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1

All-near-infrared multiphoton microscopy interrogates intact tissues at deeper imaging depths than conventional single- and two-photon near-infrared excitation microscopes  

PubMed Central

Abstract. The era of molecular medicine has ushered in the development of microscopic methods that can report molecular processes in thick tissues with high spatial resolution. A commonality in deep-tissue microscopy is the use of near-infrared (NIR) lasers with single- or multiphoton excitations. However, the relationship between different NIR excitation microscopic techniques and the imaging depths in tissue has not been established. We compared such depth limits for three NIR excitation techniques: NIR single-photon confocal microscopy (NIR SPCM), NIR multiphoton excitation with visible detection (NIR/VIS MPM), and all-NIR multiphoton excitation with NIR detection (NIR/NIR MPM). Homologous cyanine dyes provided the fluorescence. Intact kidneys were harvested after administration of kidney-clearing cyanine dyes in mice. NIR SPCM and NIR/VIS MPM achieved similar maximum imaging depth of ?100???m. The NIR/NIR MPM enabled greater than fivefold imaging depth (>500???m) using the harvested kidneys. Although the NIR/NIR MPM used 1550-nm excitation where water absorption is relatively high, cell viability and histology studies demonstrate that the laser did not induce photothermal damage at the low laser powers used for the kidney imaging. This study provides guidance on the imaging depth capabilities of NIR excitation-based microscopic techniques and reveals the potential to multiplex information using these platforms. PMID:24150231

Sarder, Pinaki; Yazdanfar, Siavash; Akers, Walter J.; Tang, Rui; Sudlow, Gail P.; Egbulefu, Christopher; Achilefu, Samuel

2013-01-01

2

Multiphoton-Excited Serotonin Photochemistry  

PubMed Central

We report photochemical and photophysical studies of a multiphoton-excited reaction of serotonin that previously has been shown to generate a photoproduct capable of emitting broadly in the visible spectral region. The current studies demonstrate that absorption of near-infrared light by an intermediate state prepared via three-photon absorption enhances the photoproduct formation yield, with the largest action cross sections (?10?19 cm2) observed at the short-wavelength limit of the titanium:sapphire excitation source. The intermediate state is shown to persist for at least tens of nanoseconds and likely to be different from a previously reported oxygen-sensitive intermediate. In addition, the two-photon fluorescence action spectrum for the fluorescent photoproduct was determined and found to have a maximum at ?780 nm (3.2 eV). A general mechanism for this photochemical process is proposed. PMID:15111435

Gostkowski, Michael L.; Allen, Richard; Plenert, Matthew L.; Okerberg, Eric; Gordon, Mary Jane; Shear, Jason B.

2004-01-01

3

Infrared multiphoton excitation and inverse electronic relaxation in SO/sub 2/  

SciTech Connect

Visible luminescence (lambda=270--470 nm) has been observed from S/sup 16/O/sub 2/ and S/sup 18/O/sub 2/ at pressures of 0.2 to 20 Torr following irradiation by an intense infrared laser (lambda=9.3 ..mu..m). Our experiments show that the luminescence is not due to dielectric breakdown or recombination of dissociation fragments, but rather is fluorescence from the first excited singlet states of SO/sub 2/ following inverse electronic relaxation from highly excited vibrational levels of the ground electronic state. Crossover from the ground to excited electronic states may also be collisionally assisted. Spectroscopic and kinetic measurements are consistent with previous studies on /sup 1/B/sub 1/ emission from SO/sub 2/. The pressure dependence of the fluorescence yield exhibits two distinct pressure regimes, while the dependence of visible emission on laser pump wavelength follows the small signal infrared absorption spectrum. The threshold for detection of fluorescence is 17--20 J/cm/sup 2/ with 9.3 ..mu..m radiation as the excitation source. These observations are discussed in terms of recently proposed theories which describe the photophysics of vibrationally excited states coupled to a radiative continuum through higher electronic states.

Wolk, G.L.; Weston, R.E. Jr.; Flynn, G.W.

1980-08-15

4

Multi-photon excitation microscopy  

PubMed Central

Multi-photon excitation (MPE) microscopy plays a growing role among microscopical techniques utilized for studying biological matter. In conjunction with confocal microscopy it can be considered the imaging workhorse of life science laboratories. Its roots can be found in a fundamental work written by Maria Goeppert Mayer more than 70 years ago. Nowadays, 2PE and MPE microscopes are expected to increase their impact in areas such biotechnology, neurobiology, embryology, tissue engineering, materials science where imaging can be coupled to the possibility of using the microscopes in an active way, too. As well, 2PE implementations in noninvasive optical bioscopy or laser-based treatments point out to the relevance in clinical applications. Here we report about some basic aspects related to the phenomenon, implications in three-dimensional imaging microscopy, practical aspects related to design and realization of MPE microscopes, and we only give a list of potential applications and variations on the theme in order to offer a starting point for advancing new applications and developments. PMID:16756664

Diaspro, Alberto; Bianchini, Paolo; Vicidomini, Giuseppe; Faretta, Mario; Ramoino, Paola; Usai, Cesare

2006-01-01

5

Multi-photon excitation microscopy.  

PubMed

Multi-photon excitation (MPE) microscopy plays a growing role among microscopical techniques utilized for studying biological matter. In conjunction with confocal microscopy it can be considered the imaging workhorse of life science laboratories. Its roots can be found in a fundamental work written by Maria Goeppert Mayer more than 70 years ago. Nowadays, 2PE and MPE microscopes are expected to increase their impact in areas such biotechnology, neurobiology, embryology, tissue engineering, materials science where imaging can be coupled to the possibility of using the microscopes in an active way, too. As well, 2PE implementations in noninvasive optical bioscopy or laser-based treatments point out to the relevance in clinical applications. Here we report about some basic aspects related to the phenomenon, implications in three-dimensional imaging microscopy, practical aspects related to design and realization of MPE microscopes, and we only give a list of potential applications and variations on the theme in order to offer a starting point for advancing new applications and developments. PMID:16756664

Diaspro, Alberto; Bianchini, Paolo; Vicidomini, Giuseppe; Faretta, Mario; Ramoino, Paola; Usai, Cesare

2006-01-01

6

Multiphoton microscopy with near infrared contrast  

E-print Network

Multiphoton microscopy with near infrared contrast agents Siavash Yazdanfar,a, * Chulmin Joo,a Chun limited to the visible spectrum. We introduce a paradigm for MPM of near-infrared NIR fluorescent Engineers. DOI: 10.1117/1.3420209 Keywords: two-photon microscopy; ultrafast fiber lasers; near-infrared

Larson-Prior, Linda

7

Infrared Multiphoton Dissociation for Quantitative Shotgun Proteomics  

PubMed Central

We modified a dual-cell linear ion trap mass spectrometer to perform infrared multiphoton dissociation (IRMPD) in the low pressure trap of a dual-cell quadrupole linear ion trap (dual cell QLT) and perform large-scale IRMPD analyses of complex peptide mixtures. Upon optimization of activation parameters (precursor q-value, irradiation time, and photon flux), IRMPD subtly, but significantly outperforms resonant excitation CAD for peptides identified at a 1% false-discovery rate (FDR) from a yeast tryptic digest (95% confidence, p = 0.019). We further demonstrate that IRMPD is compatible with the analysis of isobaric-tagged peptides. Using fixed QLT RF amplitude allows for the consistent retention of reporter ions, but necessitates the use of variable IRMPD irradiation times, dependent upon precursor mass-to-charge (m/z). We show that IRMPD activation parameters can be tuned to allow for effective peptide identification and quantitation simultaneously. We thus conclude that IRMPD performed in a dual-cell ion trap is an effective option for the large-scale analysis of both unmodified and isobaric-tagged peptides. PMID:22480380

Ledvina, Aaron R.; Lee, M. Violet; McAlister, Graeme C.; Westphall, Michael S.; Coon, Joshua J.

2012-01-01

8

Infrared multiphoton dissociation for quantitative shotgun proteomics.  

PubMed

We modified a dual-cell linear ion trap mass spectrometer to perform infrared multiphoton dissociation (IRMPD) in the low-pressure trap of a dual-cell quadrupole linear ion trap (dual-cell QLT) and perform large-scale IRMPD analyses of complex peptide mixtures. Upon optimization of activation parameters (precursor q-value, irradiation time, and photon flux), IRMPD subtly, but significantly, outperforms resonant-excitation collisional-activated dissociation (CAD) for peptides identified at a 1% false-discovery rate (FDR) from a yeast tryptic digest (95% confidence, p = 0.019). We further demonstrate that IRMPD is compatible with the analysis of isobaric-tagged peptides. Using fixed QLT rf amplitude allows for the consistent retention of reporter ions, but necessitates the use of variable IRMPD irradiation times, dependent upon precursor mass to charge (m/z). We show that IRMPD activation parameters can be tuned to allow for effective peptide identification and quantitation simultaneously. We thus conclude that IRMPD performed in a dual-cell ion trap is an effective option for the large-scale analysis of both unmodified and isobaric-tagged peptides. PMID:22480380

Ledvina, Aaron R; Lee, M Violet; McAlister, Graeme C; Westphall, Michael S; Coon, Joshua J

2012-05-15

9

Peak Multiphoton Excitation of mCherry Using an Optical Parametric Oscillator (OPO)  

PubMed Central

mCherry is a red fluorescent protein which is bright, photostable, and has a low molecular weight. It is an attractive choice for multiphoton fluorescence imaging; however, the multiphoton excitation spectrum of mCherry is not known. In this paper we report the two photon excitation spectrum of mCherry measured up to 1190 nm in the near infrared (NIR) region. Skin tissues of transgenic mice that express mCherry were used in the experiments. mCherry in the tissues was excited with a Titanium: Sapphire laser and an optical parametric oscillator pumped by the Titanium:Sapphire laser. We found that the peak excitation of mCherry occurs at 1160 nm. PMID:19590939

Culver, James C.; Gao, Liang; Anhut, Tiemo; Dickinson, Mary E.

2011-01-01

10

Multiphoton ionization and excitation spectroscopy of molecules in liquids. [Fluoranthene  

SciTech Connect

The two-photon ionization and excitation spectra of fluoranthene in liquid n-pentane have been measured and together with laser power versus signal intensity measurements have been utilized to elucidate the multiphoton ionization mechanism for this and other molecules in liquids.

Siomos, K.; Faidas, H.; Christophorou, L.G.

1984-01-01

11

Multiphoton excitation of organic chromophores in microbubble resonators  

NASA Astrophysics Data System (ADS)

We report the observation of multiphoton excitation of organic chromophores in microbubble whispering gallery mode resonators. High-Q microbubble resonators are a formed by heating a pressurized fused silica capillary to form a hollow bubble which can be filled with liquid. In this case, the microbubble is filled with a solution of Rhodamine 6G dye. The resonator and dye are excited by evanescently coupling CW light from a 980nm laser diode using a tapered optical fiber. The two-photon fluorescence of the dye can be seen with pump powers as low as 1 mW.

Cohoon, Gregory A.; Kieu, Khanh; Norwood, Robert A.

2014-03-01

12

Control of multiphoton molecular excitation with shaped femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

The work presented in this dissertation describes the use of shaped femtosecond laser pulses to control the outcome of nonlinear optical process and thus to achieve the selectivity for multiphoton molecular transitions. This research could lead to applications in various fields including nonlinear optical spectroscopy, chemical identification, biological imaging, communications, photodynamic therapy, etc. In order to realize accurate pulse shaping of the femtosecond laser pulses, it is essential to measure and correct the spectral phase distortion of such pulses. A method called multiphoton intrapulse interference phase scan is used to do so throughout this dissertation. This method is highly accurate and reproducible, and has been proved in this work to be compatible with any femtosecond pulses regardless of bandwidth, intensity and repetition rate of the laser. The phase control of several quasi-octave laser sources is demonstrated in this dissertation, with the generation of 4.3 fs and 5.9 fs pulses that reach the theoretically predicted transform-limited pulse duration. The excellent phase control achieved also guarantees the reproducibility for selective multiphoton excitations by accurate phase and/or amplitude shaping. Selective two-photon excitation, stimulated Raman scattering and coherent anti-Stokes Raman scattering with a single broadband laser source are demonstrated in this dissertation. Pulse shaping is used to achieve a fast and robust approach to measure the two-photon excitation spectrum from fluorescent molecules, which provide important information for two-photon biological imaging. The selective excitation concept is also applied in the field of remote chemical identification. Detection of characteristic Raman lines for several chemicals using a single beam coherent anti-Stokes Raman scattering spectroscopy from a 12 meter standoff distance is shown, providing a promising approach to standoff detection of chemicals, hazardous contaminations, and explosives.

Xu, Bingwei

13

Infrared multiphoton dissociation spectrum of isolated protonated 1-azapyrene  

NASA Astrophysics Data System (ADS)

The infrared spectrum of protonated 1-azapyrene has been obtained by infrared multiphoton dissociation (IRMPD) spectroscopy using a Fourier-transform ion cyclotron resonance mass spectrometer coupled to an infrared tunable free electron laser. Found when electrospraying a pyrene/methanol/acetic acid solution, the carrier of the dominant m/z 204 peak was determined by comparison of the IRMPD spectrum with density functional theory calculations (B3LYP/6-31G(d,p)). The greater proton affinity and solubility of 1-azapyrene explains the competitive protonation of azapyrene over pyrene despite its apparent smaller abundance in the electrospray solution. The possible contribution of 1-azapyrene to the interstellar infrared emission bands is briefly discussed.

Vala, Martin; Szczepanski, Jan; Dunbar, Robert; Oomens, Jos; Steill, Jeffrey D.

2009-04-01

14

Multiphoton dissociation and thermal unimolecular reactions induced by infrared lasers. [REAMPA code  

SciTech Connect

Multiphoton dissociation (MPD) of ethyl chloride was studied using a tunable 3.3 ..mu..m laser to excite CH stretches. The absorbed energy increases almost linearly with fluence, while for 10 ..mu..m excitation there is substantial saturation. Much higher dissociation yields were observed for 3.3 ..mu..m excitation than for 10 ..mu..m excitation, reflecting bottlenecking in the discrete region of 10 ..mu..m excitation. The resonant nature of the excitation allows the rate equations description for transitions in the quasicontinuum and continuum to be extended to the discrete levels. Absorption cross sections are estimated from ordinary ir spectra. A set of cross sections which is constant or slowly decreasing with increasing vibrational excitation gives good fits to both absorption and dissociation yield data. The rate equations model was also used to quantitatively calculate the pressure dependence of the MPD yield of SF/sub 6/ caused by vibrational self-quenching. Between 1000-3000 cm/sup -1/ of energy is removed from SF/sub 6/ excited to approx. > 60 kcal/mole by collision with a cold SF/sub 6/ molecule at gas kinetic rate. Calculation showed the fluence dependence of dissociation varies strongly with the gas pressure. Infrared multiphoton excitation was applied to study thermal unimolecular reactions. With SiF/sub 4/ as absorbing gas for the CO/sub 2/ laser pulse, transient high temperature pulses were generated in a gas mixture. IR fluorescence from the medium reflected the decay of the temperature. The activation energy and the preexponential factor of the reactant dissociation were obtained from a phenomenological model calculation. Results are presented in detail. (WHK)

Dai, H.L.

1981-04-01

15

Near-infrared femtosecond laser machining initiated by ultraviolet multiphoton ionization  

E-print Network

Near-infrared femtosecond laser machining initiated by ultraviolet multiphoton ionization X. Yu, Q://apl.aip.org/features/most_downloaded Information for Authors: http://apl.aip.org/authors #12;Near-infrared femtosecond laser machining initiated, and the near-infrared pulse utilizes these electrons to cause damage by avalanche ionization. VC 2013 American

Van Stryland, Eric

16

Infrared multiphoton dissociation of RDX in a molecular beam  

SciTech Connect

Infrared multiphoton dissociation (IRMPD) of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a molecular beam has been performed in order to investigate the mechanism of RDX thermal decomposition. A beam of molecules was crossed by a pulsed TEA CO/sub 2/ laser and velocity distributions of the various products were measured by the time-of-flight (TOF) technique as a function of the laboratory angle using a mass spectrometric detector. The dissociation channels, their branching ratios, and the translational energy distributions of the products were determined. In contrast to the conventional view of simple bond rupture through loss of NO/sub 2/ as the dominant primary channel in RDX decomposition, it was found that the dominant primary channel is concerted symmetric triple fission to produce three CH/sub 2/N/sub 2/O/sub 2/ fragments which subsequently undergo secondary concerted dissociation to produce HCN, H/sub 2/CO, HONO (or HNO/sub 2/), and N/sub 2/O. A total of two primary and four secondary dissociation channels were observed. Concerted reactions predominate over simple bond rupture not only in the number of channels (four vs two) but also in the amount of products. A fair amount of translational energy release through concerted reaction channels was observed, which is significant for an explanation of the energies of RDX decomposition.

Zhao, X.; Hintsa, E.J.; Lee, Y.T.

1988-01-15

17

ELECTRON DETACHMENT DISSOCIATION AND INFRARED MULTIPHOTON DISSOCIATION OF HEPARIN TETRASACCHARIDES  

PubMed Central

Heparin glycosaminoglycans (GAGs) present the most difficult glycoform for analytical characterization due to high levels of sulfation and structural heterogeneity. Recent contamination of the clinical heparin supply and subsequent fatalities has highlighted the need for sensitive methodologies of analysis. In the last decade, tandem mass spectrometry has been increasingly applied for the analysis of GAGs, but developments in the characterization of highly sulfated compounds have been minimal due to the low number of cross-ring cleavages generated by threshold ion activation by collisional induced dissociation (CID). In the current work, electron detachment dissociation (EDD) and infrared multiphoton dissociation (IRMPD) are applied to a series of heparin tetrasaccharides. With both activation methods, abundant glycosidic and cross-ring cleavages are observed. The concept of Ionized Sulfate Criteria (ISC) is presented as a succinct method for describing the charge state, degree of ionization and sodium/proton exchange in the precursor ion. These factors contribute to the propensity for useful fragmentation during MS/MS measurements. Precursors with ISC values of 0 are studied here, and shown to yield adequate structural information from ion activation by EDD or IRMPD. PMID:22247649

Leach, Franklin E.; Xiao, Zhongping; Laremore, Tatiana N.; Linhardt, Robert J.; Amster, I. Jonathan

2011-01-01

18

Fermi-coupled spherically adapted effective states in the collisionless multiphoton excitation of SF 6  

NASA Astrophysics Data System (ADS)

A calculation method for the collisionless multiphoton excitation of SF 6 by intense CO 2 laser light up to a chain of parallel nv3, ( n - 1) v3 + v2 + v6 … vibrational-rotational ladders linked by Fermi interaction is described. Spherically adapted effective states suitable to the purpose are defined, and matrix elements for multiphoton excitation in the rotatingwave approximation effective hamiltonian formalism are given in this basis. The method is aimed at the investigation of population transfer between the cited parallel vibrational ladders, and is suitable for computer-calculation programmation.

Di Lauro, C.; Lattanzi, F.

1982-10-01

19

Creation of coherent superposition states in hydrogenlike ions via multiphoton resonant excitation  

SciTech Connect

On the basis of the analytical solution of the Dirac equation the resonant multiphoton excitation of highly charged hydrogenlike ions in a strong high-frequency laser field is investigated. It is shown that the dynamics of the relativistic system is equivalent to two independent four-level systems (in the electrical-dipole approximation). The time evolution of the system is found using the nonperturbative resonant approach. We predict that due to multiphoton excitation by an appropriate laser pulse one can achieve various coherent superposition states in atomic or ionic systems with a high nuclear charge.

Avetissian, H. K.; Mkrtchian, G. F.; Poghosyan, M. G. [Department of Quantum Electronics, Yerevan State University, 1 A. Manukian St., Yerevan 375025 (Armenia)

2006-06-15

20

Thermodynamic approach for laser action and (vibrational) multiphoton excitation  

NASA Astrophysics Data System (ADS)

Using the framework of statistical mechanics, the laser is treated as a thermodynamical machine which converts heat into electromagnetic energy. Conditions are defined for smooth emission and for spontaneous pulsing (relaxation oscillation). The treatment allows precise predictions about the phase fluctuations of the produced radiation. The results are applied to the action of laser radiaton of molecular oscillators. The role of phase fluctuations on the process of multiphoton absorption of energy is stressed.

de Hemptinne, X.

1983-07-01

21

Ionization and Fragmentation of C60 via Multiphoton-Multiplasmon Excitation  

Microsoft Academic Search

We study the intensity dependence of ionization and fragmentation of buckminsterfullerene ( C60) in strong laser fields. Our data provide strong evidence that at intensities <~1014 W\\/cm2 these processes occur predominantly via multiphoton excitation of the 20 eV plasmon resonance of C60. At least two plasmons have to be created to initiate fragmentation or multiple ionization.

S. Hunsche; T. Starczewski; A. L'Huillier; A. Persson; C.-G. Wahlström; H. B. van Linden van den Heuvell; S. Svanberg

1996-01-01

22

Time-resolved infrared fluorescence from an IR multiphoton dissociation product of trifluoroacetic anhydride  

NASA Astrophysics Data System (ADS)

Infrared multiphoton dissociation of trifluoroacetic anhydride by a pulse CO 2 yields CF 3COF, C 2F 4 and CO 2 as the major, and COF 2, CO and C 2F 6 as minor photoproducts. Infrared fluorescence from a photoproduct, COF 2, is observed. The intermolecular V ? V and V ? T relaxation rate constants are calculated to be 8×10 4 and 3×10 4 s -1 Torr -1, respectively.

Kumar, Awadhesh; Vatsa, R. K.; Naik, P. D.; Rama Rao, K. V. S.; Mittal, J. P.

1992-12-01

23

Ionization and Fragmentation of {ital C}{sub {bold 60}} via Multiphoton-Multiplasmon Excitation  

SciTech Connect

We study the intensity dependence of ionization and fragmentation of buckminsterfullerene (C{sub 60}) in strong laser fields. Our data provide strong evidence that at intensities {approx_lt}10{sup 14}W/cm{sup 2} these processes occur predominantly via multiphoton excitation of the 20eV plasmon resonance of C{sub 60}. At least two plasmons have to be created to initiate fragmentation or multiple ionization. {copyright} {ital 1996 The American Physical Society.}

Hunsche, S.; Starczewski, T.; lHuillier, A.; Persson, A.; Wahlstroem, C.; van Linden van den Heuvell, H.B.; Svanberg, S. [FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (The Netherlands)] [FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (The Netherlands); [Department of Physics, Lund Institute of Technology, P.O. Box 118, S-221 00 Lund (Sweden)

1996-09-01

24

Measurement of Normal and Anomalous Diffusion of Dyes within Protein Structures Fabricated via Multiphoton Excited Cross-Linking  

Microsoft Academic Search

We demonstrate microscale spatial and chemical control of diffusion within protein matrixes created through the use of nonlinear multiphoton excited photochemistry. The mobility of fluorescent dyes of different mass and composition within controlled cross-linked environments has been measured using two-photon excited fluorescence recovery after photobleaching (FRAP). The diffusion times for several rhodamine and sulforhodamine dyes within these fabricated structures were

Swarna Basu; Charles W. Wolgemuth; Paul J. Campagnola

2004-01-01

25

Nonperturbative quantum and classical calculations of multiphoton vibrational excitation and dissociation of Morse molecules^1  

NASA Astrophysics Data System (ADS)

The multiphoton vibrational excitation and dissociation of Morse molecules have been computed nonperturbatively using Hamilton's and Schr?dinger's time-dependent equations, for a range of laser pulse parameters. The time-dependent Schr?dinger equation is solved by the state-specific expansion approach [e.g.,1]. For its solution, emphasis has been given on the inclusion of the continuous spectrum, whose contribution to the multiphoton probabilities for resonance excitation to a number of excited discrete states as well as to dissociation has been examined as a function of laser intensity, frequency and pulse duration. An analysis of possible quantal-classical correspondences for this system is being carried out. We note that distinct features exist from previous classical calculations [2]. For example, the dependence on the laser frequency gives rise to an asymmetry around the red-shifted frequency corresponding to the maximum probability. [1] Th. Mercouris, I. D. Petsalakis and C. A. Nicolaides, J. Phys. B 27, L519 (1994). [2] V. Constantoudis and C. A. Nicolaides, Phys. Rev. E 64, 562112 (2001). ^1This work was supported by the program 'Pythagoras' which is co - funded by the European Social Fund (75%) and Natl. Resources (25%). ^2Physics Department, National Technical University, Athens, Greece.^3Theoretical and Physical Chemistry Institute, Hellenic Research Foundation, Athens, Greece.

Dimitriou, K. I.; Mercouris, Th.; Constantoudis, V.; Komninos, Y.; Nicolaides, C. A.

2006-05-01

26

Generation of harmonics via multiphoton resonant excitation of hydrogenlike ions in an x-ray free-electron-laser field  

NASA Astrophysics Data System (ADS)

The coherent radiation spectrum of highly charged hydrogenlike ions in an intense x-ray free-electron-laser field is considered. The spectrum corresponding to harmonic generation in the resonant multiphoton excitation regime is investigated both analytically and numerically, arising from the Dirac Hamiltonian. The obtained analytical results are based on the generalized rotating wave approximation and are in good agreement with performed numerical calculations. Estimations show that one can achieve efficient generation of coherent hard x-ray radiation using multiphoton resonant excitation by appropriate x-ray pulses.

Avetissian, H. K.; Avchyan, B. R.; Mkrtchian, G. F.

2014-11-01

27

Nonlinear structured-illumination enhanced temporal focusing multiphoton excitation microscopy with a digital micromirror device  

PubMed Central

In this study, the light diffraction of temporal focusing multiphoton excitation microscopy (TFMPEM) and the excitation patterning of nonlinear structured-illumination microscopy (NSIM) can be simultaneously and accurately implemented via a single high-resolution digital micromirror device. The lateral and axial spatial resolutions of the TFMPEM are remarkably improved through the second-order NSIM and projected structured light, respectively. The experimental results demonstrate that the lateral and axial resolutions are enhanced from 397 nm to 168 nm (2.4-fold) and from 2.33 ?m to 1.22 ?m (1.9-fold), respectively, in full width at the half maximum. Furthermore, a three-dimensionally rendered image of a cytoskeleton cell featuring ~25 nm microtubules is improved, with other microtubules at a distance near the lateral resolution of 168 nm also able to be distinguished. PMID:25136483

Cheng, Li-Chung; Lien, Chi-Hsiang; Da Sie, Yong; Hu, Yvonne Yuling; Lin, Chun-Yu; Chien, Fan-Ching; Xu, Chris; Dong, Chen Yuan; Chen, Shean-Jen

2014-01-01

28

Multiphoton excitation and photodynamic activity of macromolecular derivatized mTHPC  

NASA Astrophysics Data System (ADS)

Multiphoton excitation of photosensitizers in photodynamic therapy constitutes a promising approach, because of the increasing tissue penetration for longer wavelength of illumination. In this contribution the photodynamic activity of polyethylene glycol macromolecular derivatized mTHPC upon two-photon excitation is established. To test the photo- activity of the photosensitizer, human colon carcinoma cells, HCT-116, were incubated with 2 (mu) g/ml of mTHPC- CMPEG4 in the nutrition medium. Subsequent pulsed laser irradiation at 784 nm focused down on growing cell monolayers restricts cell vitality clearly within 24 hours after irradiation. To investigate whether an anoxic or euoxic energy transfer mechanism is involved, a uric acid assay was performed to test for the generation of singlet oxygen. Upon single-photon excitation mTHPC-CMPEG4 in TriPEG decomposed uric acid via the generation of singlet oxygen. Using femtosecond pulsed laser irradiation no decomposition of the uric acid was found, implying an anoxic energy transfer mechanism after tow-photon excitation. However, at present, we cannot exclude local hyperthermic effects in the cells containing the photosensitizer to contribute to the photodynamic activity upon two-photon excitation.

Schneider, Marc; Graschew, Georgi; Roelofs, Theo A.; Balanos, Evangelos; Rakowsky, Stefan; Sinn, Hanns-joerg; Schlag, Peter M.

2000-03-01

29

Multiphoton versus single-photon excitation of photosensitizers for laser-induced fluorescence diagnosis and photodynamic therapy of cancer cells  

NASA Astrophysics Data System (ADS)

In laser-induced fluorescence diagnosis and photodynamic therapy of cancer the applied photosensitizers (PS) are often covalently derivatized with macromolecules to improve their selective accumulation in the cancerous tissue, while maintaining its single-photon excited photophysical properties. In this contribution methoxy-polyethylene glycol (MPEG, MW ~5 kDa) and human serum albumin (HSA, MW ~60 kDa) are used as PS carriers. Multiphoton (MP) excitation of the PS is favorable as compared to single-photon excitation because the penetration depth of the laser light is improved (>5 mm) due to the longer wavelength of the ~200 fs laser pulses used in this case (700-1050 nm). In this study cotton fibers and silica gel beads (<20 mm) were stained with various PS and multiphoton-induced fluorescence was detected with a MP laser scanning microscope. The slopes of the log-log plots of the detected fluorescence intensity versus the laser excitation intensity vary between 1.8-2.6 for the various PS investigated. The excitation wavelength dependence of the MP-induced fluoresence indicates that the excitation cross section maxima can be shifted substantially relative to twice the wavelength of the one-photon absorption maxima. Some PS (photofrin II, purpurin, mTHPC-[MPEG]2 and diaminoanthra-quinone) do not exhibit multiphoton-induced fluorescence. Some derivatized PS (sulforhodamine B, erythrosin B, purpurin) exhibit MP-induced fluorescence, although no single-photon absorption band exists in the spectral region around half the excitation wavelength

Roelofs, Theo A.; Graschew, Georgi; Schneider, Marc; Rakowsky, Stefan; Sinn, Hanns-joerg; Schlag, Peter M.

2001-04-01

30

Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation  

PubMed Central

Multicolor nonlinear microscopy of living tissue using two- and three-photon-excited intrinsic fluorescence combined with second harmonic generation by supermolecular structures produces images with the resolution and detail of standard histology without the use of exogenous stains. Imaging of intrinsic indicators within tissue, such as nicotinamide adenine dinucleotide, retinol, indoleamines, and collagen provides crucial information for physiology and pathology. The efficient application of multiphoton microscopy to intrinsic imaging requires knowledge of the nonlinear optical properties of specific cell and tissue components. Here we compile and demonstrate applications involving a range of intrinsic molecules and molecular assemblies that enable direct visualization of tissue morphology, cell metabolism, and disease states such as Alzheimer's disease and cancer. PMID:12756303

Zipfel, Warren R.; Williams, Rebecca M.; Christie, Richard; Nikitin, Alexander Yu; Hyman, Bradley T.; Webb, Watt W.

2003-01-01

31

Feasibility of using multiphoton excited tissue autofluorescence for in vivo human histopathology.  

PubMed Central

Rapid and direct imaging of microscopic tissue morphology and pathology can be achieved by multiphoton imaging of intrinsic tissue fluorophores and second harmonic signals. Engineering parameters for developing this technology for clinical applications include excitation levels and collection efficiencies required to obtain diagnostic quality images from different tissue types and whether these levels are mutagenic. Here we provide data on typical average powers required for high signal-to-noise in vivo tissue imaging and assess the risk potential of these irradiance levels using a mammalian cell gene mutation assay. Exposure times of ~16 milliseconds per cell to 760 nm, ~200 fs raster-scanned laser irradiation delivered through a 0.75 NA objective produced negligible mutagenicity at powers up to about 50 mW. PMID:21258552

Dela Cruz, Johanna M.; McMullen, Jesse D.; Williams, Rebecca M.; Zipfel, Warren R.

2010-01-01

32

Properties of crosslinked protein matrices for tissue engineering applications synthesized by multiphoton excitation.  

PubMed

We demonstrate the fabrication of model scaffolds and extracellular matrices using multiphoton excited photochemistry. This method is three-dimensional in nature and has excellent biocompatibility. Crosslinked matrices were fabricated from the proteins fibrinogen, fibronectin, and concanavalin A using two-photon rose bengal photoactivation and the relatives rates were determined. Immunofluorescence labeling of fibrinogen and fibronectin indicated retention of bioactivity following the multiphoton crosslinking process. Using the fluorescence recovery after photobleaching method, we measured the lateral mobility of fluorescent dyes of different mass and chemistry in order to model the behavior of therapeutic agents and bioactive molecules and found diffusion coefficients within these fabricated structures to be on the order of 10(-9)-10(-10) cm(2)/s, or approximately three to four orders of magnitude slower than in free solution. The precise diffusion coefficients can be smoothly tuned by varying the laser exposure during the fabrication of the matrix, which results in both an increase in crosslink density as well as protein concentration in the matrix. Terminal crosslink density is achieved at integrated high exposure dose and the relative fabrication rates were determined for these proteins. For all the proteins, the range of diffusion coefficients between the threshold for fabrication and the terminal limit is correlated with the change in matrix mesh size as determined by Flory-Rehner swelling analysis. Both normal Fickian as well as hindered anomalous diffusion is observed depending on specific molecular interactions of the tracer dyes and protein host. (c) 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 359-368, 2004. PMID:15376265

Basu, Swarna; Campagnola, Paul J

2004-11-01

33

Photodissociation dynamics of nitromethane and methyl nitrite by infrared multiphoton dissociation imaging with quasiclassical trajectory calculations: Signatures of the roaming pathway  

NASA Astrophysics Data System (ADS)

We combine the techniques of infrared multiphoton dissociation (IRMPD) with state selective ion imaging to probe roaming dynamics in the unimolecular dissociation of nitromethane and methyl nitrite. Recent theoretical calculations suggest a "roaming-mediated isomerization" pathway of nitromethane to methyl nitrite prior to decomposition. State-resolved imaging of the NO product coupled with infrared multiphoton dissociation was carried out to examine this unimolecular decomposition near threshold. The IRMPD images for the NO product from nitromethane are consistent with the earlier IRMPD studies that first suggested the importance of an isomerization pathway. A significant ?-doublet propensity is seen in nitromethane IRMPD but not methyl nitrite. The experimental observations are augmented by quasiclassical trajectory calculations for nitromethane and methyl nitrite near threshold for each dissociation pathway. The observation of distinct methoxy vibrational excitation for trajectories from nitromethane and methyl nitrite dissociation at the same total energy show that the nitromethane dissociation bears a nonstatistical signature of the roaming isomerization pathway, and this is possibly responsible for the nitromethane ?-doublet propensity as well.

Dey, Arghya; Fernando, Ravin; Abeysekera, Chamara; Homayoon, Zahra; Bowman, Joel M.; Suits, Arthur G.

2014-02-01

34

Photodissociation dynamics of nitromethane and methyl nitrite by infrared multiphoton dissociation imaging with quasiclassical trajectory calculations: signatures of the roaming pathway.  

PubMed

We combine the techniques of infrared multiphoton dissociation (IRMPD) with state selective ion imaging to probe roaming dynamics in the unimolecular dissociation of nitromethane and methyl nitrite. Recent theoretical calculations suggest a "roaming-mediated isomerization" pathway of nitromethane to methyl nitrite prior to decomposition. State-resolved imaging of the NO product coupled with infrared multiphoton dissociation was carried out to examine this unimolecular decomposition near threshold. The IRMPD images for the NO product from nitromethane are consistent with the earlier IRMPD studies that first suggested the importance of an isomerization pathway. A significant ?-doublet propensity is seen in nitromethane IRMPD but not methyl nitrite. The experimental observations are augmented by quasiclassical trajectory calculations for nitromethane and methyl nitrite near threshold for each dissociation pathway. The observation of distinct methoxy vibrational excitation for trajectories from nitromethane and methyl nitrite dissociation at the same total energy show that the nitromethane dissociation bears a nonstatistical signature of the roaming isomerization pathway, and this is possibly responsible for the nitromethane ?-doublet propensity as well. PMID:24511938

Dey, Arghya; Fernando, Ravin; Abeysekera, Chamara; Homayoon, Zahra; Bowman, Joel M; Suits, Arthur G

2014-02-01

35

Biosensing and -imaging with enantiomeric luminescent conjugated polythiophenes using multiphoton excitation  

NASA Astrophysics Data System (ADS)

We report on the initial time-resolved luminescense and nonlinear absorption properties of two polythiophenes 3-substituted with chiral charged amino acid-derivatized substituents, POWT and POMT. The photo-physical characterization yielded quantum efficiency typically in the range 0.01 - 0.1, however, with two-photon absorption cross-section better than or similar to a typical two-photon reference chromophore, such as fluorescein. They were tested as conformational sensitive optical probes for the recording of pH-induced conformational changes of synthetic peptides, proteins and samples of protein amyloid fibrils characteristic of amyloid related diseases. Particularly, the POMT polyelectrolyte with the L-enantiomeric side chains is shown to favor this induction of well defined structure as judged by the circular dichroic signal as well as a stronger enhancement of luminescense for the L-form over the D-form complex. Furthermore, time-resolved fluorescense and two-photon induced fluorescence both also showed a difference in the complexation with the D and L form. This shows that the multi-photon excitation path can be an efficient means for chiral recognition of biomolecular complexes. It is demonstrated how the conjugated polyelectrolyte L-POMT can be used to spectrally image the formation of amyloid fibrils of insulin using both one- and two-photon absorption based fluorescence imaging.

Lindgren, Mikael; Stabo-Eeg, Frantz; Schnell, Edrun A.; Nilsson, K. Peter R.; Hammarstrom, Per; Inganaes, Olle

2005-08-01

36

Nonperturbative methods in the problem of multiphoton excitation of atom by squeezed light  

NASA Technical Reports Server (NTRS)

Multiphoton detectors for the strong squeezed light vacuum are considered. The result is compared with the perturbation theory. It is shown that as the degree of squeezing is increased the statistical factor decreases.

Belousov, A. V.; Kovarsky, V. A.

1993-01-01

37

Chirped pulse multiphoton ionization of nitrogen: control of selective rotational excitation in N(2)(+)(B 2Sigma(u)(+)).  

PubMed

We report on fluorescence spectra of N(2)(+)(B (2)Sigma(u)(+)) --> N(2)(+)(X (2)Sigma(g)(+)) obtained from multiphoton ionization of molecular nitrogen by 804 nm femtosecond laser pulses. The analysis of the fluorescence spectra reveals that the vibrational levels v = 0 and v = 4 in the B (2)Sigma(u)(+)-state of N(2)(+) are primarily populated. The rotational state distribution of N(2)(+)(B (2)Sigma(u)(+), v = 0) is determined from the rotationally resolved fluorescence spectra. It is demonstrated that the linear chirp of the 804 nm femtosecond laser pulse has a strong influence on the rotational state distribution of the vibrational ground state of the molecular cation N(2)(+)(B (2)Sigma(u)(+), v = 0). Possible mechanisms leading to the experimental results are discussed. The particular population of the vibrational levels as well as the linear chirp dependence of the fluorescence signal gives evidence for the importance of a resonant intermediate state. The N(2) a (1)Pi-state is likely involved in a resonant multiphoton excitation process. This permits to selectively control the rotational population of the cation that is formed via chirped pulse multiphoton ionization. PMID:19566159

Plenge, J; Wirsing, A; Raschpichler, C; Meyer, M; Rühl, E

2009-06-28

38

Application of Infrared Multiphoton Dissociation Spectroscopy for the Study of Chiral Recognition in Protonated Serine Clusters  

NASA Astrophysics Data System (ADS)

Serine is an amino acid which has long been known to form "magic-number" ionic clusters, serine octamer [Ser_8 + H]^+. It has been shown that serine octamers exhibit strong preference for homochirality, but its structure is still unclear. We have used infrared multiphoton dissociation (IRMPD) spectroscopic technique coupled with a Fourier transform ion cyclotron (FRICR) mass spectrometer to investigate the structures of protonated serin octamer and dimer as well as the chiral recognition in these clusters. With the use of ICR cell, the ions can be stored for a sufficient time so that measurements of IRMPD spectra become possible with a CW OPO laser in the 3000-4000 cm-1 region. As an aid to interpret the observed spectra, molecular structures and vibrational frequencies of the octamer and dimer have been predicted by using the B3LYP/6-311++G** calculations. Differences in chiral selectivity between the serine octamer and dimer will be discussed. S. C. Nanita and R. G. Cooks Angew. Chem. Int. Ed. 45(554), 2006.

Sunahori, Fumie X.; Yang, Guochun; Kitova, Elena N.; Klassen, John S.; Xu, Yunjie

2010-06-01

39

Chirality recognition of the protonated serine dimer and octamer by infrared multiphoton dissociation spectroscopy.  

PubMed

Infrared multiphoton dissociation (IRMPD) spectroscopy has been used to record IR signatures of chirality recognition in the protonated serine dimer and octamer in the 3200-3800 cm(-1) region. This is the first IRMPD study to investigate the heterochiral biomolecular system by utilizing the isotope-labelled species. Noticeable differences in the homo- versus heterochiral IRMPD spectra have been obtained experimentally for both the dimer and octamer. Different dissociation patterns have been noted not only between the homo- and heterochiral octamers, but also between the two -OH stretching vibrational bands of the same chirality species. Systematic theoretical searches have been carried out to identify the most stable conformers of both the homo- and heterochiral protonated serine dimer and octamer. The final geometry optimization and harmonic vibrational calculations have been performed at the MP2/6-311++G(d,p) level for the homo- and heterochiral protonated serine dimer and at the B3LYP/6-31G(d) level for the homo- and heterochiral protonated serine octamer. For the homo- and heterochiral dimer, good agreement between the experimental and theoretical spectra has been achieved and the major conformers have been identified. For the homo- and heterochiral octamer, the main IR features observed have been satisfactorily reproduced theoretically and the dominant conformers identified. More than one main conformer has been identified for the homochiral octamer. This conclusion has been further supported by the analysis of the wavelength specific dissociation products. PMID:23247298

Sunahori, Fumie X; Yang, Guochun; Kitova, Elena N; Klassen, John S; Xu, Yunjie

2013-02-14

40

Oxygen isotope separation utilizing two-frequency infrared multiphoton dissociation of 2,3-dihydropyran  

NASA Astrophysics Data System (ADS)

Oxygen isotope separation has been examined by utilizing the two-frequency infrared multiphoton dissociation (IRMPD) of 2,3-dihydropyran (DHP). The two-frequency IRMPD reduces the required laser fluences to those lower than the damage threshold of optical windows. For example, dissociation probability of DHP containing 18O (D(18O)) and enrichment factor (S) were obtained to be 1.6×10-3/pulse and 316, respectively, by the simultaneous irradiation with 1052.2 cm-1 photons at 0.45 J/cm2 and 1031.5 cm-1 photons at 1.06 J/cm2. These are comparable with D(18O)=2.2×10-3/pulse and S=391 obtained by the single-frequency irradiation of 1033.5 cm-1 photons at 2.2 J/cm2. Therefore, the production rate of an 18O enriched dissociation product has been increased to four times or more, compared with the single-frequency IRMPD, and this two-frequency method would promise a practical large scale separation.

Hashimoto, M.; Ohba, H.; Yokoyama, A.

2011-09-01

41

Multiphoton tomography for tissue engineering  

NASA Astrophysics Data System (ADS)

Femtosecond laser multiphoton tomography has been employed in the field of tissue engineering to perform 3D high-resolution imaging of the extracellular matrix proteins elastin and collagen as well as of living cells without any fixation, slicing, and staining. Near infrared 80 MHz picojoule femtosecond laser pulses are able to excite the endogenous fluorophores NAD(P)H, flavoproteins, melanin, and elastin via a non-resonant two-photon excitation process. In addition, collagen can be imaged by second harmonic generation. Using a two-PMT detection system, the ratio of elastin to collagen was determined during optical sectioning. A high submicron spatial resolution and 50 picosecond temporal resolution was achieved using galvoscan mirrors and piezodriven focusing optics as well as a time-correlated single photon counting module with a fast microchannel plate detector and fast photomultipliers. Multiphoton tomography has been used to optimize the tissue engineering of heart valves and vessels in bioincubators as well as to characterize artificial skin. Stem cell characterization and manipulation are of major interest for the field of tissue engineering. Using the novel sub-20 femtosecond multiphoton nanoprocessing laser microscope FemtOgene, the differentiation of human stem cells within spheroids has been in vivo monitored with submicron resolution. In addition, the efficient targeted transfection has been demonstrated. Clinical studies on the interaction of tissue-engineered products with the natural tissue environment can be performed with in vivo multiphoton tomograph DermaInspect.

König, Karsten

2008-02-01

42

The theoretical concept of multipho-ton excitation was first proposed by  

E-print Network

the optical-sectioning ability of multiphoton imaging. Laser light focused on the specimen through advantages accrue sec- ondarily from the use of long excita- tion wavelengths: 1) Light scattering declines-Mayer in 1931 (11) but was not experimentally proven until the invention of the laser 30 years later, and even

Parker, Ian

43

Acylated glucosinolates with diverse acyl groups investigated by high resolution mass spectrometry and infrared multiphoton dissociation.  

PubMed

With the aim of developing a procedure for detecting and identifying intact acylated glucosinolates (a-GLSs) found in trace quantities in natural plant samples, extracts of Barbarea vulgaris seeds were analyzed by reversed-phase liquid chromatography coupled with electrospray ionization and Fourier-transform ion cyclotron resonance mass spectrometry (RPLC-ESI FTICR MS). After a preliminary optimization of fragmentation conditions, based on a non-acylated parent glucosinolate (glucobarbarin) and three previously identified a-GLSs (the 6'-isoferuloyl esters of glucobarbarin, gluconasturtiin and glucobrassicin), infrared multiphoton dissociation (IRMPD) was employed for a tandem MS-based elucidation of the molecular structures of novel a-GLSs. As a result, three acylated derivatives of glucobarbarin, esterified at the thioglucose moiety with a coumaric acid isomer, sinapic acid or an isomer and a dimethoxycinnamic acid isomer, were identified. In addition, a further acylated glucosinolate was tentatively identified as the isoferuloyl ester of an unidentified hydroxylic derivative of glucobarbarin. This is the first demonstration of diversity in the acyl moieties of thioglucose-acylated glucosinolates, which may reflect the substrate specificity of the endogenous acyl transferase. As expected, 6'-isoferuloyl-glucobarbarin was detected as the main acylated GLS in extracts of B. vulgaris seeds. A quantitative estimate suggested that non-isoferuloyl substituted glucobarbarins correspond to ca. 0.026% of the level of 6'-isoferuloyl glucobarbarin. The formation of an uncommon distonic radical anion, most likely generated in the gas phase upon methyl radical (CH3·) loss from the isoferuloyl anion, is demonstrated. PMID:24512839

Bianco, Giuliana; Agerbirk, Niels; Losito, Ilario; Cataldi, Tommaso R I

2014-04-01

44

Quantum dot infrared photodetector enhanced by surface plasma wave excitation  

E-print Network

Quantum dot infrared photodetector enhanced by surface plasma wave excitation S. C. Lee, S. Krishna: Up to a thirty-fold detectivity enhancement is achieved for an InAs quantum dot infrared photodetector (QDIP) by the excitation of surface plasma waves (SPWs) using a metal photonic crystal (MPC

Krishna, Sanjay

45

Carcinogenic damage to deoxyribonucleic acid is induced by near-infrared laser pulses in multiphoton microscopy via combination of two- and three-photon absorption.  

PubMed

Nonlinear optical imaging modalities (multiphoton excited fluorescence, second and third harmonic generation) applied in vivo are increasingly promising for clinical diagnostics and the monitoring of cancer and other disorders, as they can probe tissue with high diffraction-limited resolution at near-infrared (IR) wavelengths. However, high peak intensity of femtosecond laser pulses required for two-photon processes causes formation of cyclobutane-pyrimidine-dimers (CPDs) in cellular deoxyribonucleic acid (DNA) similar to damage from exposure to solar ultraviolet (UV) light. Inaccurate repair of subsequent mutations increases the risk of carcinogenesis. In this study, we investigate CPD damage that results in Chinese hamster ovary cells in vitro from imaging them with two-photon excited autofluorescence. The CPD levels are quantified by immunofluorescent staining. We further evaluate the extent of CPD damage with respect to varied wavelength, pulse width at focal plane, and pixel dwell time as compared with more pronounced damage from UV sources. While CPD damage has been expected to result from three-photon absorption, our results reveal that CPDs are induced by competing twoand three-photon absorption processes, where the former accesses UVA absorption band. This finding is independently confirmed by nonlinear dependencies of damage on laser power, wavelength, and pulse width. PMID:23214185

Nadiarnykh, Oleg; Thomas, Giju; Van Voskuilen, Johan; Sterenborg, Henricus J C M; Gerritsena, Hans C

2012-11-01

46

Carcinogenic damage to deoxyribonucleic acid is induced by near-infrared laser pulses in multiphoton microscopy via combination of two- and three-photon absorption  

NASA Astrophysics Data System (ADS)

Nonlinear optical imaging modalities (multiphoton excited fluorescence, second and third harmonic generation) applied in vivo are increasingly promising for clinical diagnostics and the monitoring of cancer and other disorders, as they can probe tissue with high diffraction-limited resolution at near-infrared (IR) wavelengths. However, high peak intensity of femtosecond laser pulses required for two-photon processes causes formation of cyclobutane-pyrimidine-dimers (CPDs) in cellular deoxyribonucleic acid (DNA) similar to damage from exposure to solar ultraviolet (UV) light. Inaccurate repair of subsequent mutations increases the risk of carcinogenesis. In this study, we investigate CPD damage that results in Chinese hamster ovary cells in vitro from imaging them with two-photon excited autofluorescence. The CPD levels are quantified by immunofluorescent staining. We further evaluate the extent of CPD damage with respect to varied wavelength, pulse width at focal plane, and pixel dwell time as compared with more pronounced damage from UV sources. While CPD damage has been expected to result from three-photon absorption, our results reveal that CPDs are induced by competing two- and three-photon absorption processes, where the former accesses UVA absorption band. This finding is independently confirmed by nonlinear dependencies of damage on laser power, wavelength, and pulse width.

Nadiarnykh, Oleg; Thomas, Giju; Van Voskuilen, Johan; Sterenborg, Henricus J. C. M.; Gerritsen, Hans C.

2012-11-01

47

COMPACT NON-CONTACT TOTAL EMISSION DETECTION FOR IN-VIVO MULTI-PHOTON EXCITATION MICROSCOPY  

PubMed Central

Summary We describe a compact, non-contact design for a Total Emission Detection (c-TED) system for intra-vital multi-photon imaging. To conform to a standard upright two-photon microscope design, this system uses a parabolic mirror surrounding a standard microscope objective in concert with an optical path that does not interfere with normal microscope operation. The non-contact design of this device allows for maximal light collection without disrupting the physiology of the specimen being examined. Tests were conducted on exposed tissues in live animals to examine the emission collection enhancement of the c-TED device compared to heavily optimized objective-based emission collection. The best light collection enhancement was seen from murine fat (5×-2× gains as a function of depth), while murine skeletal muscle and rat kidney showed gains of over two and just under two-fold near the surface, respectively. Gains decreased with imaging depth (particularly in the kidney). Zebrafish imaging on a reflective substrate showed close to a two-fold gain throughout the entire volume of an intact embryo (approximately 150 ?m deep). Direct measurement of bleaching rates confirmed that the lower laser powers (enabled by greater light collection efficiency) yielded reduced photobleaching in vivo. The potential benefits of increased light collection in terms of speed of imaging and reduced photo-damage, as well as the applicability of this device to other multi-photon imaging methods is discussed. PMID:24251437

Glancy, Brian; Karamzadeh, Nader S.; Gandjbakhche, Amir H.; Redford, Glen; Kilborn, Karl; Knutson, Jay R.; Balaban, Robert S.

2014-01-01

48

Femtosecond infrared intrastromal ablation and backscattering-mode adaptive-optics multiphoton microscopy in chicken corneas  

PubMed Central

The performance of femtosecond (fs) laser intrastromal ablation was evaluated with backscattering-mode adaptive-optics multiphoton microscopy in ex vivo chicken corneas. The pulse energy of the fs source used for ablation was set to generate two different ablation patterns within the corneal stroma at a certain depth. Intrastromal patterns were imaged with a custom adaptive-optics multiphoton microscope to determine the accuracy of the procedure and verify the outcomes. This study demonstrates the potential of using fs pulses as surgical and monitoring techniques to systematically investigate intratissue ablation. Further refinement of the experimental system by combining both functions into a single fs laser system would be the basis to establish new techniques capable of monitoring corneal surgery without labeling in real-time. Since the backscattering configuration has also been optimized, future in vivo implementations would also be of interest in clinical environments involving corneal ablation procedures. PMID:22076258

Gualda, Emilio J.; Vázquez de Aldana, Javier R.; Martínez-García, M. Carmen; Moreno, Pablo; Hernández-Toro, Juan; Roso, Luis; Artal, Pablo; Bueno, Juan M.

2011-01-01

49

Theory of the effect of odd-photon destructive interference on optical shifts in resonantly enhanced multiphoton excitation and ionization  

NASA Astrophysics Data System (ADS)

We present a theory for two- and three-photon excitation, optical shifting, and four-wave mixing when a first laser is tuned onto, or near, a two-photon resonance and a second much more intense laser is tuned near or on resonance between the two-photon resonance and a second excited state. When the second excited state has a dipole-allowed transition back to the ground state and the concentration is sufficiently high, a destructive interference is produced between three-photon coupling of the ground state and the second excited state and one-photon coupling between the same states by the internally generated four-wave mixing field. This interference leads to several striking effects. For instance, as the onset of the interference occurs, the optical shifts in the two-photon resonance excitation line shape become smaller in copropagating geometry so that the line shapes for multiphoton ionization enhanced by the two-photon resonance eventually become unaffected by the second laser. In the same range of concentrations the four-wave mixing field evolves to a concentration-independent intensity. With counterpropagating laser beams the line shape exhibits normal optical shifts like those observed for both copropagating and counterpropagating laser beams at very low concentrations. The theoretical work presented here extends our earlier works by including the effect of laser bandwidth and by removing the restriction of having the second laser be tuned far from three-photon resonance. In this way we have now included, as a special case, the effect of both laser bandwidth and interference on laser-induced transparency. Unlike other effects related to odd-photon destructive interference, the effect of a broad bandwidth is to bring about the predicted effects at much lower concentrations. Studies in rubidium show good agreement between theory and experiment for both ionization line shapes and four-wave mixing intensity as a function of concentration.

Payne, M. G.; Deng, Lu; Garrett, W. R.

1998-08-01

50

Practical Method for Producing a Large Amount of Isotopically Enriched Silicon by Infrared Multi-Photon Dissociation of Hexafluorodisilane  

NASA Astrophysics Data System (ADS)

This paper presents a practical method for producing highly enriched silicon isotopes utilizing laser irradiation. One- or two-frequency CO2 laser irradiation has been employed to separate the desired isotope of silicon by means of infrared multi-photon dissociation (IRMPD) of hexafluorodisilane (Si2F6) molecules using a flow reaction system. The production of Si2F6 with a 28Si fraction of 99.1% at a rate of 0.67 g (28Si)/h was successfully accomplished with a yield of about 63% by two-frequency laser irradiation. Enriched SiF4 gas with 30Si exceeding 31% was also continuously obtained at a production rate of 0.12 g/h by one-frequency laser irradiation.

Ohba, Hironori; Akagi, Hiroshi; Katsumata, Keiichi; Hashimoto, Masashi; Yokoyama, Atsushi

2008-11-01

51

Cascade Dissociations of Peptide Cation-Radicals. Part2. Infrared Multiphoton Dissociation and Mechanistic Studies of z-Ions from Pentapeptides  

PubMed Central

Dissociations of z4 ions from pentapeptides AAXAR, where X = H, Y, F, W, and V, produce dominant z2 ions that account for >50% of the fragment ion intensity. The dissociation has been studied in detail by experiment and theory and found to involve several isomerization and bond-breaking steps. Isomerizations in z4 ions proceed by amide transcis rotations followed by radical-induced transfer of a ?-hydrogen atom from the side chain, forming stable C? radical intermediates. These undergo rate-determining cleavage of the C?—CO bond at the X residue followed by loss of the neutral AX fragment, forming x2 intermediates. The latter were detected by energy-resolved resonant excitation collision-activated dissociation (CAD) and infrared multiphoton dissociation (IRMPD) experiments. The x2 intermediates undergo facile loss of HNCO to form z2 fragment ions, as also confirmed by energy-resolved CAD and IRMPD MS4 experiments. The loss of HNCO from the x2 ion from AAHWR is kinetically hampered by the Trp residue that traps the OCNH radical group in a cyclic intermediate. PMID:22669762

Ledvina, Aaron R.; Chung, Thomas W.; Hui, Renjie; Coon, Joshua J.

2013-01-01

52

Cascade dissociations of peptide cation-radicals. Part 2. Infrared multiphoton dissociation and mechanistic studies of z-ions from pentapeptides.  

PubMed

Dissociations of z(4) ions from pentapeptides AAXAR where X=H, Y, F, W, and V produce dominant z(2) ions that account for >50 % of the fragment ion intensity. The dissociation has been studied in detail by experiment and theory and found to involve several isomerization and bond-breaking steps. Isomerizations in z(4) ions proceed by amide trans?cis rotations followed by radical-induced transfer of a ?-hydrogen atom from the side chain, forming stable C(?) radical intermediates. These undergo rate-determining cleavage of the C(?)-CO bond at the X residue followed by loss of the neutral AX fragment, forming x(2) intermediates. The latter were detected by energy-resolved resonant excitation collision-induced dissociation (CID) and infrared multiphoton dissociation (IRMPD) experiments. The x(2) intermediates undergo facile loss of HNCO to form z(2) fragment ions, as also confirmed by energy-resolved CID and IRMPD MS(4) experiments. The loss of HNCO from the x(2) ion from AAHWR is kinetically hampered by the Trp residue that traps the OCNH radical group in a cyclic intermediate. PMID:22669762

Ledvina, Aaron R; Chung, Thomas W; Hui, Renjie; Coon, Joshua J; Ture?ek, Frantisek

2012-08-01

53

Cascade Dissociations of Peptide Cation-Radicals. Part 2. Infrared Multiphoton Dissociation and Mechanistic Studies of z-Ions from Pentapeptides  

NASA Astrophysics Data System (ADS)

Dissociations of z 4 ions from pentapeptides AAXAR where X = H, Y, F, W, and V produce dominant z 2 ions that account for >50 % of the fragment ion intensity. The dissociation has been studied in detail by experiment and theory and found to involve several isomerization and bond-breaking steps. Isomerizations in z 4 ions proceed by amide trans?cis rotations followed by radical-induced transfer of a ?-hydrogen atom from the side chain, forming stable C? radical intermediates. These undergo rate-determining cleavage of the C?-CO bond at the X residue followed by loss of the neutral AX fragment, forming x 2 intermediates. The latter were detected by energy-resolved resonant excitation collision-induced dissociation (CID) and infrared multiphoton dissociation (IRMPD) experiments. The x 2 intermediates undergo facile loss of HNCO to form z 2 fragment ions, as also confirmed by energy-resolved CID and IRMPD MS4 experiments. The loss of HNCO from the x 2 ion from AAHWR is kinetically hampered by the Trp residue that traps the OCNH radical group in a cyclic intermediate.

Ledvina, Aaron R.; Chung, Thomas W.; Hui, Renjie; Coon, Joshua J.; Ture?ek, Frantisek

2012-08-01

54

Measurement of normal and anomalous diffusion of dyes within protein structures fabricated via multiphoton excited cross-linking.  

PubMed

We demonstrate microscale spatial and chemical control of diffusion within protein matrixes created through the use of nonlinear multiphoton excited photochemistry. The mobility of fluorescent dyes of different mass and composition within controlled cross-linked environments has been measured using two-photon excited fluorescence recovery after photobleaching (FRAP). The diffusion times for several rhodamine and sulforhodamine dyes within these fabricated structures were found to be approximately 3-4 orders of magnitude slower than in free solution. The precise diffusion times can be tuned by varying the laser exposure during the fabrication of the matrix, and the diffusion can be correlated with the mesh size determined by TEM and Flory-Rehner analysis. We find that the hydrophobic Texas Red dyes (sulforhodamines) exhibit diffusion that is highly anomalous, indicative of a strong interaction with the hydrophobic cross-linked protein matrix. These results suggests the use of these cross-linked protein matrixes as ideal model systems in which to systematically study anomalous diffusion. Finally, the diffusion can be tuned within a multilayered protein matrix, and this in conjunction with slow diffusion also suggests the use of these structures in controlled release applications. PMID:15530051

Basu, Swarna; Wolgemuth, Charles W; Campagnola, Paul J

2004-01-01

55

Simulation-based investigation of the three-dimensional distribution of fluorescence and photobleaching in multi-photon excited samples  

NASA Astrophysics Data System (ADS)

We present a numerical study on the spatial distribution of fluorescence and photobleaching occurring in samples subject to multi-photon excitation. We developed a simulation model and implemented a simulator program. Its quantitative predictions can help to find the optimal operating parameters (such as laser power, pulse length, pulse repetition rate) of the two-photon microscope to reach higher image quality, to reduce undesired photobleaching, and to pave the way for optimized photoswitching-based super-resolution imaging. Conversely, the simulator might also be useful when photodynamic parameters are searched for. Furthermore, such simulations can promote the evaluation of the results of other fluorescence-based techniques [e.g. fluorescence recovery after photobleaching (FRAP) measurements]. The photodynamic model of the fluorophore contains a ground state, an excited state, a triplet state, and several photobleached states; the state transitions are characterized by absorption cross sections and lifetimes. The sample is modeled as a fluorophore solution divided into cubic cells among which diffusion takes place. The illumination is simulated as a focused laser pulse train described by a pulsed Gaussian beam. As a demonstration of the capabilities of the simulator, an example is presented that reveals the spatial distribution of photon emission in the sample investigated by a two-photon microscope in the case of different laser and photobleaching parameters, assuming one-photon absorption induced photobleaching. The simulation demonstrates quantitatively how photobleaching affects the spatial distribution of fluorescence and the resolution of the microscope.

Juhász, Imre B.; Csurgay, Árpád. I.

2014-05-01

56

Direct observation of the vibrational energy redistribution in (CF3)2CCO molecules resonantly excited by femtosecond infrared laser radiation  

NASA Astrophysics Data System (ADS)

The dynamics of multiphoton excitation of (CF3)2CCO molecules has been investigated under the condition of resonant action of femtosecond infrared laser radiation on the ?1 vibrational mode of the C=C=O bond. It has been shown that the mode-selective excitation of this vibration occurs up to the ? = 6 level. The kinetics of the subsequent intramolecular vibrational energy redistribution from the ?1 mode has been measured. A value of 5 ± 0.3 ps has been obtained for the characteristic time of this process.

Kompanets, V. O.; Laptev, V. B.; Makarov, A. A.; Pigulsky, S. V.; Ryabov, E. A.; Chekalin, S. V.

2010-10-01

57

Application of Infrared Multiphoton Dissociation Spectroscopy for the Study of Chiral Recognition in the Protonated Serine Clusters: Part II  

NASA Astrophysics Data System (ADS)

Serine is an amino acid which has long been known to form the magic-number serine octamer [Ser_8 + H]^+. It has been shown that the serine octamer exhibits strong preference for homochirality. Although a few possible structures for the homochiral serine octamer have been proposed, no definite conclusion has so far been drawn. Last year at this conference, we reported on the study of the protonated serine octamer and dimer as well as the chiral recognition in these clusters using infrared multiphoton dissociation (IRMPD) spectroscopic technique coupled with a Fourier transform ion cyclotron (FTICR) mass spectrometer. Here we present our latest results on the search for the infrared signatures of chiral recognition in the serine octamer and the dimer using a mixture of the deuterated 2,3,3-d_3-L-serine and normal D-serine solution. Using the isotopic labeled species, we could isolate the heterochiral species and obtain their IRMPD spectra which can be directly compared with those of the homochiral species. As an aid to interpret the observed spectra, molecular structures and vibrational frequencies of both homochiral and heterochiral octamer and dimer have been predicted by ab initio calculations. New insights into the hitherto undetermined structure of the serine octamer will be discussed. S. C. Nanita and R. G. Cooks Angew. Chem. Int. Ed. 45, (554), 2006.

Sunahori, Fumie X.; Kitova, Elena N.; Klassen, John S.; Xu, Yunjie; Yang, Guochun

2011-06-01

58

Multi-photon molecular tagging velocimetry with femtosecond excitation (FemtoMTV)  

NASA Astrophysics Data System (ADS)

We present results for first molecular tagging velocimetry (MTV) measurements in water under resonant femtosecond excitation/emission process of a phosphorescent supramolecule. Both two-photon and three-photon absorption processes are examined, and the feasibility of measurements is demonstrated by single component velocimetry in a simple jet flow. The new capabilities enabled by FemtoMTV include elimination of the need for short wavelength UV excitation source and UV optical access in flow facilities, and potential for high rep-rate flow imaging.

Pouya, Shahram; Van Rhijn, Alexander; Dantus, Marcos; Koochesfahani, Manoochehr

2014-08-01

59

Measurement of Normal and Anomalous Diffusion of Dyes within Protein Structures Fabricated via Multiphoton Excited  

E-print Network

confined to the plane of focus through precise control of the laser power, just as in the more commonMeasurement of Normal and Anomalous Diffusion of Dyes within Protein Structures Fabricated via and composition within controlled cross-linked environments has been measured using two-photon excited

Wolgemuth, Charles

60

Multi-photon molecular tagging velocimetry with femtosecond excitation (FemtoMTV)  

E-print Network

on linear, single-photon excitation pro- cesses. This includes laser-induced fluorescence (LIF) techniques- locimetry in a simple jet flow. The new capabilities enabled by FemtoMTV include elimination of the need. 1983), and its single-beam implementation using sub-10 fs pulses (Roy et al. 2009). In MTV, long

Koochesfahani, Manoochehr M.

61

Infrared light excites cells by changing their electrical capacitance.  

PubMed

Optical stimulation has enabled important advances in the study of brain function and other biological processes, and holds promise for medical applications ranging from hearing restoration to cardiac pace making. In particular, pulsed laser stimulation using infrared wavelengths >1.5 ?m has therapeutic potential based on its ability to directly stimulate nerves and muscles without any genetic or chemical pre-treatment. However, the mechanism of infrared stimulation has been a mystery, hindering its path to the clinic. Here we show that infrared light excites cells through a novel, highly general electrostatic mechanism. Infrared pulses are absorbed by water, producing a rapid local increase in temperature. This heating reversibly alters the electrical capacitance of the plasma membrane, depolarizing the target cell. This mechanism is fully reversible and requires only the most basic properties of cell membranes. Our findings underscore the generality of pulsed infrared stimulation and its medical potential. PMID:22415827

Shapiro, Mikhail G; Homma, Kazuaki; Villarreal, Sebastian; Richter, Claus-Peter; Bezanilla, Francisco

2012-01-01

62

INFLUENCE OF CHARGE STATE AND SODIUM CATIONIZATION ON THE ELECTRON DETACHMENT DISSOCIATION AND INFRARED MULTIPHOTON DISSOCIATION OF GLYCOSAMINOGLYCAN OLIGOSACCHARIDES  

PubMed Central

Electron detachment dissociation (EDD) Fourier transform mass spectrometry has recently been shown to be a useful method for tandem mass spectrometry analysis of sulfated glycosaminoglycans (GAGs). EDD produces abundant glycosidic and cross-ring fragmentation that is useful for localizing sites of sulfation in GAG oligosaccharides. While EDD fragmentation can be used to characterize GAGs in a single tandem mass spectrometry experiment, SO3 accompanies many peaks, and complicates the resulting mass spectra. In this work we demonstrate the ability to significantly decrease SO3 loss by selection of the proper ionized state of GAG precursor ions. When the degree of ionization is greater than the number of sulfate groups in an oligosaccharide, a significant reduction in SO3 loss is observed in the EDD mass spectra. This data suggested that SO3 loss is reduced when an electron is detached from carboxylate groups instead of sulfate. Electron detachment occurs preferentially from carboxylate versus sulfate for thermodynamic reasons, provided that carboxylate is in its ionized state. Ionization of the carboxylate group is achieved by selecting the appropriate precursor ion charge state, or by the replacement of protons with sodium cations. Increasing the ionization state by sodium cation addition decreases, but does not eliminate, SO3 loss from infrared multiphoton dissociation (IRMPD) of the same GAG precursor ions. PMID:18499037

Wolff, Jeremy J.; Laremore, Tatiana N.; Busch, Alexander M.; Linhardt, Robert J.; Amster, I. Jonathan

2008-01-01

63

Infrared multiphoton dissociation in quadrupole time-of-flight mass spectrometry: top-down characterization of proteins.  

PubMed

The first implementation of infrared multiphoton dissociation (IRMPD) for a hybrid quadrupole time-of-flight (QqTOF) mass spectrometer is reported. Ions were trapped in the radio frequency-only quadrupole (q2), which normally serves as a collision cell, and irradiated by a continuous CO2 IR laser. The laser beam was introduced coaxially with the quadrupoles in order to maximize overlap with the ion path. The resolution of the TOF mass analyzer allowed direct charge state determination for fragments smaller than 7 kDa. For larger fragments, the charge state could be assigned using the multiple losses of water, characteristic for IRMPD of proteins. The analytical performance is demonstrated by top-down sequencing of several representative proteins (equine myoglobin, bovine casein, and human insulin and chaperonin 10). Various post-translational modifications such as phosphorylation, acetylation, formation of disulfide bridges, and removal of N-terminal methionine followed by acetylation are detected and characterized. The utility of IRMPD for the analysis of biological samples is demonstrated in a study of a recently identified potential marker for endometrial cancer, chaperonin 10. PMID:16808467

Raspopov, Serguei A; El-Faramawy, Ayman; Thomson, Bruce A; Siu, K W Michael

2006-07-01

64

Differentiation and distributions of DNA/cisplatin crosslinks by liquid chromatography-electrospray ionization-infrared multiphoton dissociation mass spectrometry.  

PubMed

Liquid chromatography-electrospray ionization-infrared multiphoton dissociation (IRMPD) mass spectrometry was developed to investigate the distributions of intrastrand crosslinks formed between cisplatin and two oligodeoxynucleotides (ODNs), d(A1T2G3G4G5T6A7C8C9C10A11T12) (G3-D) and its analog d(A1T2G3G4G5T6T7C8C9C10A11T12) (G3-H), which have been reported to adopt different secondary structures in solution. Based on the formation of site-specific fragment ions upon IRMPD, two isobaric crosslink products were differentiated for each ODN. The preferential formation of G3G4 and G4G5 crosslinks was determined as a function of reaction conditions, including incubation temperature and presence of metal ions. G3-D consistently exhibited a greater preference for formation of the G4G5 crosslink compared with the G3-H ODN. The ratio of G3G4:G4G5 crosslinks increased for both G3-D and G3-H at higher incubation temperatures or when metal salts were added. Comparison of the IRMPD fragmentation patterns of the unmodified ODNs and the intramolecular platinated crosslinks indicated that backbone cleavage was significantly suppressed near the crosslink. PMID:24135806

Xu, Zhe; Brodbelt, Jennifer S

2014-01-01

65

Differentiation and Distributions of DNA/Cisplatin Crosslinks by Liquid Chromatography-Electrospray Ionization-Infrared Multiphoton Dissociation Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Liquid chromatography-electrospray ionization-infrared multiphoton dissociation (IRMPD) mass spectrometry was developed to investigate the distributions of intrastrand crosslinks formed between cisplatin and two oligodeoxynucleotides (ODNs), d(A1T2G3G4G5T6A7C8C9C10A11T12) (G3-D) and its analog d(A1T2G3G4G5T6T7C8C9C10A11T12) (G3-H), which have been reported to adopt different secondary structures in solution. Based on the formation of site-specific fragment ions upon IRMPD, two isobaric crosslink products were differentiated for each ODN. The preferential formation of G3G4 and G4G5 crosslinks was determined as a function of reaction conditions, including incubation temperature and presence of metal ions. G3-D consistently exhibited a greater preference for formation of the G4G5 crosslink compared with the G3-H ODN. The ratio of G3G4:G4G5 crosslinks increased for both G3-D and G3-H at higher incubation temperatures or when metal salts were added. Comparison of the IRMPD fragmentation patterns of the unmodified ODNs and the intramolecular platinated crosslinks indicated that backbone cleavage was significantly suppressed near the crosslink.

Xu, Zhe; Brodbelt, Jennifer S.

2014-01-01

66

Differentiation and Distributions of DNA/Cisplatin Crosslinks by Liquid Chromatography-Electrospray Ionization-Infrared Multiphoton Dissociation Mass Spectrometry  

PubMed Central

Liquid chromatography-electrospray ionization-infrared multiphoton dissociation (IRMPD) mass spectrometry was developed to investigate the distributions of intrastrand crosslinks formed between cisplatin and two oligodeoxynucleotides (ODNs), d(A1T2G3G4G5T6A7C8C9C10A11T12) (G3-D) and its analog d(A1T2G3G4G5T6T7C8C9C10A11T12) (G3-H), that have been reported to adopt different secondary structures in solution. Based on the formation of site-specific fragment ions upon IRMPD, two isobaric crosslink products were differentiated for each ODN. The preferential formation of G3G4 and G4G5 crosslinks was determined as a function of reaction conditions, including incubation temperature and presence of metal ions. G3-D consistently exhibited a greater preference for formation of the G4G5 crosslink compared to the G3-H ODN. The ratio of G3G4:G4G5 crosslinks increased for both G3-D and G3-H at higher incubation temperatures or when metal salts were added. Comparison of the IRMPD fragmentation patterns of the unmodified ODNs and the intramolecular platinated crosslinks indicated that backbone cleavage was significantly suppressed near the crosslink. PMID:24135806

Xu, Zhe; Brodbelt, Jennifer S.

2013-01-01

67

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Carbon isotope separation by infrared multiphoton dissociation of CF2HCl molecules with a separation reactor in a laser cavity  

NASA Astrophysics Data System (ADS)

An investigation was made of isotopically selective multiphoton dissociation of CF2HCl molecules by high-intensity infrared radiation in a separation reactor placed inside the cavity of a TEA CO2 laser. Special attention was paid to the influence of the laser system parameters (linear and nonlinear cavity losses, input energy) on the time and spatial characteristics of the laser radiation, and to the dependences of the characteristics of an elementary isotope separation event (selectivity and dissociation yield) on these laser parameters. The intracavity position of the separation reactor made it possible to reach high energy densities in large volumes, to utilise efficiently the laser radiation, and to achieve high values of the selectivity (in excess of 100) and yield (over 5%) of the multiphoton dissociation process. The conditions of operation of this laser system were optimised in respect of the input energy and the CF2HCl pressure in the separation reactor.

Lokhman, V. N.; Makarov, Grigorii N.; Ryabov, Evgenii A.; Sotnikov, M. V.

1996-01-01

68

Infrared imaging results of an excited planar jet  

NASA Astrophysics Data System (ADS)

Planar jets are used for many applications including heating, cooling, and ventilation. Generally such a jet is designed to provide good mixing within an enclosure. In building applications, the jet provides both thermal comfort and adequate indoor air quality. Increased mixing rates may lead to lower short-circuiting of conditioned air, elimination of dead zones within the occupied zone, reduced energy costs, increased occupant comfort, and higher indoor air quality. This paper discusses using an infrared imaging system to show the effect of excitation of a jet on the spread angle and on the jet mixing efficiency. Infrared imaging captures a large number of data points in real time (over 50,000 data points per image) providing significant advantages over single-point measurements. We used a screen mesh with a time constant of approximately 0.3 seconds as a target for the infrared camera to detect temperature variations in the jet. The infrared images show increased jet spread due to excitation of the jet. Digital data reduction and analysis show change in jet isotherms and quantify the increased mixing caused by excitation.

Farrington, R. B.

1991-12-01

69

Fragmentation of Singly, Doubly, and Triply Charged Hydrogen Deficient Peptide Radical Cations in Infrared Multiphoton Dissociation and Electron Induced Dissociation  

NASA Astrophysics Data System (ADS)

Gas phase fragmentation of hydrogen deficient peptide radical cations continues to be an active area of research. While collision induced dissociation (CID) of singly charged species is widely examined, dissociation channels of singly and multiply charged radical cations in infrared multiphoton dissociation (IRMPD) and electron induced dissociation (EID) have not been, so far, investigated. Here, we report on the gas phase dissociation of singly, doubly and triply charged hydrogen deficient peptide radicals, [M + nH](n+1)+· ( n = 0, 1, 2), in MS3 IRMPD and EID and compare the observed fragmentation pathways to those obtained in MS3 CID. Backbone fragmentation in MS3 IRMPD and EID was highly dependent on the charge state of the radical precursor ions, whereas amino acid side chain cleavages were largely independent of the charge state selected for fragmentation. Cleavages at aromatic amino acids, either through side chain loss or backbone fragmentation, were significantly enhanced over other dissociation channels. For singly charged species, the MS3 IRMPD and EID spectra were mainly governed by radical-driven dissociation. Fragmentation of doubly and triply charged radical cations proceeded through both radical- and charge-driven processes, resulting in the formation of a wide range of backbone product ions including, a-, b-, c-, y-, x-, and z-type. While similarities existed between MS3 CID, IRMPD, and EID of the same species, several backbone product ions and side chain losses were unique for each activation method. Furthermore, dominant dissociation pathways in each spectrum were dependent on ion activation method, amino acid composition, and charge state selected for fragmentation.

Kalli, Anastasia; Hess, Sonja

2012-02-01

70

A New FRAP\\/FRAPa Method for Three-Dimensional Diffusion Measurements Based on Multiphoton Excitation Microscopy  

Microsoft Academic Search

We present a new convenient method for quantitative three-dimensionally resolved diffusion measurements based on the photobleaching (FRAP) or photoactivation (FRAPa) of a disk-shaped area by the scanning laser beam of a multiphoton microscope. Contrary to previously reported spot-photobleaching protocols, this method has the advantage of full scalability of the size of the photobleached area and thus the range of diffusion

Davide Mazza; Kevin Braeckmans; Francesca Cella; Ilaria Testa; Dries Vercauteren; J. Demeester; Stefaan S. De Smedt; Alberto Diaspro

2008-01-01

71

SPONTANEOUS RAMAN AND COHERENT ANTI-STOKES RAMAN SPECTROSCOPY OF INFRARED MULTIPHOTON EXCITED MOLECULES  

E-print Network

and rigorousness in scientific research. It has been a pleasure to collaborate with Professor Mary Shultz. Her Street, Somerville was indispensable during the past five years. My landlady Margaret Waller taught me

Mazur, Eric

72

Multiphoton microscopy in neuroscience  

NASA Astrophysics Data System (ADS)

The study of the nervous system requires to an exceptional extent observation of and experimentation on intact tissue. There, in particular, high-resolution optical microscopy benefits from the inherent advantages of multi-photon fluorescence excitation. Several cases will be presented from a number of different tissues and organisms, where multi-photon excited laser scanning fluorescence microscopy has been an essential experimental tool. Those examples include the discovery of biochemical coincidence detection in synaptic spines and the clarification of the underlying mechanism; the observation of sensory evoked dendritic signaling in intact animals and the observation of light induced calcium signals in the intact retina. Recently a fiber coupled two-photon microscopy has been developed that allows the imaging in moving animal.

Denk, Winfried

2002-06-01

73

TESTING MODELS OF LOW-EXCITATION PHOTODISSOCIATION REGIONS WITH FAR-INFRARED OBSERVATIONS OF REFLECTION NEBULAE  

E-print Network

emission in the far-infrared ( $ 30 200 lm). Far-infrared (FIR) spectroscopy is a standard toolTESTING MODELS OF LOW-EXCITATION PHOTODISSOCIATION REGIONS WITH FAR-INFRARED OBSERVATIONS nebulae. These observations include the far-infrared atomic fine-structure lines of [O i] 63 and 145 lm

Rudolph, Alexander L.

74

Infrared multiphoton induced isomerization and dissociation of FCN, ClCN, and BrCN in liquid Ar: A classical simulation study  

SciTech Connect

We report the results of classical mechanics simulations of infrared multiphoton induced control of isomerization of FCN, ClCN, and BrCN in liquid Ar, using ab initio potential energy and dipole moment surfaces for the XCN molecules. The field induced isomerization and fragmentation dynamics of these molecules are found to be different from that of HCN in liquid Ar. In particular, the scheme that provides complete controlled conversion of HCN to CNH in liquid Ar fails to generate complete conversion of XCN to CNX in liquid Ar for X=F,Cl,Br. It is suggested that the sources of the differences in behavior arise from differences in the spectra of vibrational nonlinear resonances in HCN and XCN and to the occurrence of monodromy in the dynamics of the XCN molecules.

Zhang Ming; Gong Jiangbin; Ma Ao; Rice, Stuart A. [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States); Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States) and James Franck Institute, University of Chicago, Chicago, Illinois 60637 (United States)

2007-10-14

75

Studies of protonated and anionic artemisinin in the gas-phase by infrared multi-photon dissociation and by negative ion photoelectron spectroscopies  

NASA Astrophysics Data System (ADS)

Protonated and anionic artemisinin in the gas phase have respectively been studied by infrared multi-photon dissociation (IRMPD) spectroscopy and by anion photoelectron spectroscopy. Comparison of the measured IRMPD spectrum with calculated spectra of various conformations showed that the two lowest-energy protonated structures, both corresponding to protonation at the C dbnd O 14 carbonyl site, were observed experimentally. The calculations also indicated that the peroxide bridge in artemisinin is only slightly modified by protonation. Additionally, stable, intact (parent) artemisinin radical anions have been obtained for the first time in the gas phase and the photoelectron spectrum supports the computational finding that the excess electron is mainly localized on the ? ? orbital of the peroxide bond. The vertical detachment energy and adiabatic electron affinity, calculated at the MP2/6-31+G ? level, are in good agreement with the experimental data and the O-O distance is calculated to be stretched by more than 50% in the anion.

Seydou, M.; Gillet, J. C.; Li, X.; Wang, H.; Posner, G. H.; Grégoire, G.; Schermann, J. P.; Bowen, K. H.; Desfrançois, C.

2007-12-01

76

Multivariate Analysis of Electron Detachment Dissociation and Infrared Multiphoton Dissociation Mass Spectra of Heparan Sulfate Tetrasaccharides Differing Only in Hexuronic acid Stereochemistry  

NASA Astrophysics Data System (ADS)

The structural characterization of glycosaminoglycan (GAG) carbohydrates by mass spectrometry has been a long-standing analytical challenge due to the inherent heterogeneity of these biomolecules, specifically polydispersity, variability in sulfation, and hexuronic acid stereochemistry. Recent advances in tandem mass spectrometry methods employing threshold and electron-based ion activation have resulted in the ability to determine the location of the labile sulfate modification as well as assign the stereochemistry of hexuronic acid residues. To facilitate the analysis of complex electron detachment dissociation (EDD) spectra, principal component analysis (PCA) is employed to differentiate the hexuronic acid stereochemistry of four synthetic GAG epimers whose EDD spectra are nearly identical upon visual inspection. For comparison, PCA is also applied to infrared multiphoton dissociation spectra (IRMPD) of the examined epimers. To assess the applicability of multivariate methods in GAG mixture analysis, PCA is utilized to identify the relative content of two epimers in a binary mixture.

Oh, Han Bin; Leach, Franklin E.; Arungundram, Sailaja; Al-Mafraji, Kanar; Venot, Andre; Boons, Geert-Jan; Amster, I. Jonathan

2011-03-01

77

Optical visualization of Alzheimer’s pathology via multiphoton-excited intrinsic fluorescence and second harmonic generation  

PubMed Central

Intrinsic optical emissions, such as autofluorescence and second harmonic generation (SHG), are potentially useful for functional fluorescence imaging and biomedical disease diagnosis for neurodegenerative diseases such as Alzheimer’s disease (AD). Here, using multiphoton and SHG microscopy, we identified sources of intrinsic emissions in ex vivo, acute brain slices from AD transgenic mouse models. We observed autofluorescence and SHG at senile plaques as well as characterized their emission spectra. The utility of intrinsic emissions was demonstrated by imaging senile plaque autofluorescence in conjunction with SHG from microtubule arrays to assess the polarity of microtubules near pathological lesions. Our results suggest that tissues from AD transgenic models contain distinct intrinsic emissions, which can provide valuable information about the disease mechanisms. PMID:19259208

Kwan, Alex C.; Duff, Karen; Gouras, Gunnar K.; Webb, Watt W.

2010-01-01

78

Investigating the central engine and excitation mechanisms of ultraluminous infrared galaxies: near-infrared spectroscopy  

NASA Astrophysics Data System (ADS)

We present near-infrared observations of a sample of mainly interacting ultraluminous infrared galaxies, comprising H- and K-band spectra. Our main aims are to investigate the power source of these extremely luminous objects and the various excitation mechanisms of the strong molecular hydrogen emission often seen in such objects. Broadened emission lines were only detected in one object, IRAS 23498, consistent with the previous results for this galaxy. The [Sivi] emission line was detected in IRAS 17179 and 20210, both classified as Sy2s. Two of the samples were unclassified, IRAS 00150 and 23420, which exhibit neither [Sivi] emission nor broadened Hi emission. However this does not rule out the presence of an obscured AGN. Analysis of the molecular hydrogen emission showed that the major excitation mechanism for most objects was thermal. Modelling of the more luminous objects indicates that for IRAS 20210 10 per cent, and for both IRAS 23365 and IRAS 23420 30 per cent, of the 1-0 S(1) line emission has a non-thermal origin.

Burston, A. J.; Ward, M. J.; Davies, R. I.

2001-09-01

79

Image reconstruction for multiphoton fluorescence microscopy  

NASA Astrophysics Data System (ADS)

We present a general image reconstruction methodology for multiphoton fluorescence microscopy. The method is primarily based on Markov random field modeling of the detected image data. Evaluation on two-photon-excitation-(TPE) and two-photon-excited-4PI-microscopy images shows high quality artifact-free reconstruction. Image reconstruction for multiphoton imaging modalities such as TPE and 4PI may find potential application in nano-bioimaging and optical imaging.

Mondal, Partha Pratim; Vicidomini, Giuseppe; Diaspro, Alberto

2008-03-01

80

Time and structural crosscorrelation image analysis of microscopic volumes, simultaneously recorded with second harmonic generation, third harmonic generation, and multiphoton excitation fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Our newly developed multimodal microscope enables simultaneous collection of second harmonic generation (SHG), third harmonic generation (THG) and multiphoton excitation fluorescence (MPF) signals. The signals can be generated within different or the same intercellular structures. In comparing two signals, traditional methods of image crosscorrelation analysis using Pearson's coefficient provide a general parameter as to whether the images are similar, however it does not give detailed information about correlation of different structures inside the images. We present here a new technique that employs a pixel by pixel analysis over an entire area or volume that is used to correlate the structures appearing in the images. The result of the analysis reveals structures within the sample that are generated by both nonlinear signals as well as highlighting the structures that are generated by only one of the nonlinear signals. The algorithm provides a means to colocalize different structures revealed by the different nonlinear contrast mechanisms. Structural correlation maps are useful in identifying the origin of structures in one nonlinear contrast mechanism when the origin of structures in another is known. Image analysis has also been exploited for sequences of images taken in time. The intensity fluctuations in time for each pixel reveal regions of intense physiological activity in biological samples. Correlation of time dependent fluctuations from different pixels in the image time series allows construction of the structural map that undergoes similar time behavior or appears out of phase. These structural correlation analysis techniques are demonstrated based on polystyrene beads and cardiomyocytes.

Greenhalgh, Catherine; Cisek, Richard; Prent, Nicole; Major, Arkady; Aus de Au, Juerg; Squier, Jeff; Barzda, Virginijus

2005-09-01

81

Ab initio study of the orientation effects in multiphoton ionization and high-order harmonic generation from the ground and excited electronic states of H2+  

E-print Network

We present an ab initio three-dimensional (3D) calculation of multiphoton ionization (MPI) and high-order harmonic generation (HHG) of the hydrogen molecular ions subject to intense linearly polarized laser pulses. The orientation of the molecular...

Chu, Shih-I; Telnov, Dmitry A.

2007-10-11

82

Assigning structures to gas-phase peptide cations and cation-radicals. An infrared multiphoton dissociation, ion mobility, electron transfer, and computational study of a histidine peptide ion.  

PubMed

Infrared multiphoton dissociation (IRMPD) spectroscopy, using a free-electron laser, and ion mobility measurements, using both drift-cell and traveling-wave instruments, were used to investigate the structure of gas-phase peptide (AAHAL + 2H)(2+) ions produced by electrospray ionization. The experimental data from the IRMPD spectra and collisional cross section (?) measurements were consistent with the respective infrared spectra and ? calculated for the lowest-energy peptide ion conformer obtained by extensive molecular dynamics searches and combined density functional theory and ab initio geometry optimizations and energy calculations. Traveling-wave ion mobility measurements were employed to obtain the ? of charge-reduced peptide cation-radicals, (AAHAL + 2H)(+?), and the c(3), c(4), z(3), and z(4) fragments from electron-transfer dissociation (ETD) of (AAHAL + 2H)(2+). The experimental ? for the ETD charge-reduced and fragment ions were consistent with the values calculated for fully optimized ion structures and indicated that the ions retained specific hydrogen bonding motifs from the precursor ion. In particular, the ? for the doubly protonated ions and charge-reduced cation-radicals were nearly identical, indicating negligible unfolding and small secondary structure changes upon electron transfer. The experimental ? for the (AAHAL + 2H)(+?) cation-radicals were compatible with both zwitterionic and histidine radical structures formed by electron attachment to different sites in the precursor ion, but did not allow their distinction. The best agreement with the experimental ? was found for ion structures fully optimized with M06-2X/6-31+G(d,p) and using both projection approximation and trajectory methods to calculate the theoretical ? values. PMID:22364440

Moss, Christopher L; Chamot-Rooke, Julia; Nicol, Edith; Brown, Jeffery; Campuzano, Iain; Richardson, Keith; Williams, Jonathan P; Bush, Matthew F; Bythell, Benjamin; Paizs, Bela; Turecek, Frantisek

2012-03-15

83

Multiphoton imaging and fluorescence lifetime studies on unstained cells and tissue at cryogenic conditions  

NASA Astrophysics Data System (ADS)

Monitoring the functional status of cryo-preserved cells and tissue in-situ, i.e. in the frozen state, might allow for optimal adjustment of preservation conditions and might provide the information necessary to predict a functionality recovery rate. Here, an imaging approach with compositional sensitivity seems favourable. In our approach we use multiphoton microscopy in combination with fluorescence lifetime imaging to investigate cells, human and plant tissue at cryogenic conditions. By the non-linearity of multiphoton excitation we largely suppress image distortions attributed to scattering of incoming light. Only where the intensity of the pulsed near-infrared laser beam is sufficiently large, significant fluorescence is excited. This allows reaching penetration depth in ice comparable to the liquid state. As additional information we use the fluorescence decay to assign compositional entities. Results obtained on cells and tissues are discussed with respect to temperature dependencies and the related use for applications.

Stark, Martin; Dörr, Daniel; Ehlers, Alexander; Sauer, Daniel; Bückle, Rainer; Martin, Sven; Ehrhart, Friederike; Baunach, Jennifer; Katsen-Globa, Alisa; Zimmermann, Heiko; König, Karsten

2007-07-01

84

Microwave multiphoton rabi oscillations  

SciTech Connect

Resonant multiphoton transitions are driven between the 21s state and the lowest energy member of the adjacent n = 19 Stark manifold in Potassium using a high intensity 9 GHz microwave field generated inside a resonant cavity. Using the linear Stark shift of the manifold state the levels can be tuned into resonance by applying a static voltage to a septum inside the cavity. Atoms are first excited to the 21s state by a laser while the microwave field is resonant. Some time later a voltage pulse applied to the cavity detunes the atoms from resonance. A high voltage pulse is then applied to ionize only the excited n = 19 atoms, which are then detected. Oscillations in the n = 19 population are observed as a function of the time the atoms spend in resonance.

Gatzke, M.; Watkins, R.B.; Gallagher, T.F.

1993-05-01

85

Multiphoton microscopy in life sciences  

Microsoft Academic Search

Summary Near infrared (NIR) multiphoton microscopy is becoming a novel optical tool of choice for fluorescence imaging with high spatial and temporal resolution, diagnostics, photo- chemistry and nanoprocessing within living cells and tissues. Three-dimensional fluorescence imaging based on non-resonant two-photon or three-photon fluorophor exci- tation requires light intensities in the range of MW cm22 to GW cm22, which can be

K. Konig

2000-01-01

86

H2 Ejection from Polycyclic Aromatic Hydrocarbons: Infrared Multiphoton Dissociation Study of Protonated Acenaphthene and 9,10-dihydrophenanthrene  

NASA Astrophysics Data System (ADS)

The infrared multiple-photon dissociation (IRMPD) spectra of protonated acenaphthene ([ACN+H]+) and 9,10-dihydrophenanthrene ([DHP+H]+) have been recorded using an infrared free electron laser after the compounds were protonated by electrospray ionization and trapped in a Fourier transform ion cyclotron mass spectrometer. In both compounds, the loss of two mass units is predominant. Density functional calculations (B3LYP/6-311++G(d,p)) of the infrared spectra of all possible protonated isomers of each species showed that the observed IRMPD spectra are best fit to the isomer with the largest proton affinity and lowest relative electronic energy. Potential energy surfaces of the most stable isomers of [ACN+H]+ and [DHP+H]+ have been calculated for H and H2 loss. The lowest energy barriers are for loss of H2, with predicted energies 4.28 and 4.15 eV, respectively. After H2 ejection, the adjacent aliphatic hydrogens migrate to the bare ejection site and stabilize the remaining fragment. Single H loss may occur from [ACN+H]+ but the energy required is higher. No single H loss is predicted from [DHP+H]+, only H migration around the carbon skeleton. The vibrational bands in the parent closed-shell protonated polycyclic aromatic hydrocarbons are compared to bands observed from the interstellar medium.

Szczepanski, Jan; Oomens, Jos; Steill, Jeffrey D.; Vala, Martin T.

2011-01-01

87

Combined infrared multiphoton dissociation and electron capture dissociation with a hollow electron beam in Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

An electron injection system based on an indirectly heated ring-shaped dispenser cathode has been developed and installed in a 7 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This new hardware design allows high-rate electron capture dissociation (ECD) to be carried out by a hollow electron beam coaxial with the ion cyclotron resonance (ICR) trap. Infrared multiphoton dissociation (IRMPD) can also be performed with an on-axis IR-laser beam passing through a hole at the centre of the dispenser cathode. Electron and photon irradiation times of the order of 100 ms are required for efficient ECD and IRMPD, respectively. As ECD and IRMPD generate fragments of different types (mostly c, z and b, y, respectively), complementary structural information that improves the characterization of peptides and proteins by FTICR mass spectrometry can be obtained. The developed technique enables the consecutive or simultaneous use of the ECD and IRMPD methods within a single FTICR experimental sequence and on the same ensemble of trapped ions in multistage tandem (MS/MS/MS or MS(n)) mass spectrometry. Flexible changing between ECD and IRMPD should present advantages for the analysis of protein digests separated by liquid chromatography prior to FTICRMS. Furthermore, ion activation by either electron or laser irradiation prior to, as well as after, dissociation by IRMPD or ECD increases the efficiency of ion fragmentation, including the w-type fragment ion formation, and improves sequencing of peptides with multiple disulfide bridges. The developed instrumental configuration is essential for combined ECD and IRMPD on FTICR mass spectrometers with limited access into the ICR trap. PMID:12872281

Tsybin, Youri O; Witt, Matthias; Baykut, Gökhan; Kjeldsen, Frank; Håkansson, Per

2003-01-01

88

Scrambling of autoinducing precursor peptides investigated by infrared multiphoton dissociation with electrospray ionization and Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

Two synthetic precursor peptides, H(2)N-CVGIW and H(2)N-LVMCCVGIW, involved in the quorum sensing of Lactobacillus plantarum WCFS1, were characterized by mass spectrometry (MS) with electrospray ionization and 7-T Fourier transform ion cyclotron resonance (ESI-FTICR) instrument. Cell-free bacterial supernatant solutions were analyzed by reversed-phase liquid chromatography with ESI-FTICR MS to verify the occurrence of both pentapeptide and nonapeptide in the bacterial broth. The structural characterization of both protonated peptides was performed by infrared multiphoton dissociation using a continuous CO(2) laser source at a wavelength of 10.6 ?m. As their fragmentation behavior cannot be directly derived from the primary peptide structure, all anomalous fragments were interpreted as neutral loss of amino acids from the interior of both peptides, i.e., loss of V, G, VG and M, MC, V, CC, from H(2)N-CVGIW and H(2)N-LVMCCVGIW, respectively. Mechanisms of this scrambling are proposed. FTICR MS provides accurate masses of all fragment ions with very low absolute mass errors (<1.6 ppm), which facilitated the reliable assignment of their elemental compositions. The resolving power was more than sufficient to resolve closely isobaric product ions with routine subparts per million mass accuracies. Only the occurrence of pentapeptide was found in the cell-free culture of L. plantarum, grown in Waymouth's medium broth, with a low content of 5.2 ± 2.6 ?M by external calibration. Most of it was present as oxidized H(2)N-CVGIW, that is, the soluble disulfide pentapeptide with a level tenfold higher (i.e., 50 ± 4 ?M, n = 3). PMID:23208287

Bianco, Giuliana; Labella, Cristiana; Pepe, Antonietta; Cataldi, Tommaso R I

2013-02-01

89

Thermodynamics of vibrational multiphoton processes  

NASA Astrophysics Data System (ADS)

On the basis of a thermodynamic treatment of driven harmonic oscillators in a coherent field it is demonstrated that resonant molecules are attracted by the high-field region of a finite-width laser beam. This phenomenon has been observed experimentally. The same thermodynamic treatment explains the pressure and the fluence dependence of "Collisionless" multiphoton excitation. Saturation phenomena (Lamb dip) are shown to be caused by the distortion of the translational velocity distribution of oscillators in a nearly resonant field.

De Hemptinne, X.

1985-02-01

90

Investigating the 3.3 micron infrared fluorescence from naphthalene following ultraviolet excitation  

NASA Technical Reports Server (NTRS)

Polycyclic aromatic hydrocarbon (PAH) type molecules are proposed as the carriers of the unidentified infrared (UIR) bands. Detailed studies of the 3.3 micrometer infrared emission features from naphthalene, the simplest PAH, following ultraviolet laser excitation are used in the interpretation of the 3.29 micrometer (3040 cm(sup -1)) UIR band. A time-resolved Fourier transform spectrometer is used to record the infrared emission spectrum of gas-phase naphthalene subsequent to ultraviolet excitation facilitated by an excimer laser operated at either 193 nm or 248 nm. The emission spectra differ significantly from the absorption spectrum in the same spectral region. Following 193 nm excitation the maximum in the emission profile is red-shifted 45 cm(sup -1) relative to the absorption maximum; a 25 cm(sup -1) red-shift is observed after 248 nm excitation. The red-shifting of the emission spectrum is reduced as collisional and radiative relaxation removes energy from the highly vibrationally excited molecules. Coupling between the various vibrational modes is thought to account for the differences between absorption and emission spectra. Strong visible emission is also observed following ultraviolet excitation. Visible emission may play an important role in the rate of radiative relaxation, which according to the interstellar PAH hypothesis occurs only by the slow emission of infrared photons. Studying the visible emission properties of PAH type molecules may be useful in the interpretation of the DIB's observed in absorption.

Williams, Richard M.; Leone, Stephen R.

1994-01-01

91

Microbeam-integrated multiphoton imaging system  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy has been added to the array of imaging techniques at the endstation for the Microbeam II cell irradiator at Columbia University's Radiological Research Accelerator Facility (RARAF). This three-dimensional (3D), laser-scanning microscope functions through multiphoton excitation, providing an enhanced imaging routine during radiation experiments with tissuelike samples, such as small living animals and organisms. Studies at RARAF focus on radiation effects; hence, this multiphoton microscope was designed to observe postirradiation cellular dynamics. This multiphoton microscope was custom designed into an existing Nikon Eclipse E600-FN research fluorescence microscope on the irradiation platform. Design details and biology applications using this enhanced 3D-imaging technique at RARAF are reviewed.

Bigelow, Alan W.; Geard, Charles R.; Randers-Pehrson, Gerhard; Brenner, David J.

2008-12-01

92

Multiphoton spectroscopy of Rydberg states of small molecules  

SciTech Connect

Multiphoton ionization techniques provide a versatile means for studying highly excited states of atoms and molecules and provide a valuable complement to traditional techniques based on single-photon absorption and ionization studies. In this paper we present the results of new multiphoton ionization studies of molecular nitrogen and molecular oxygen that serve to illustrate the power of these techniques. 30 refs., 3 figs.

Pratt, S.T.; McCormack, E.F.; Dehmer, J.L.; Dehmer, P.M.

1990-01-01

93

High multi-photon visible upconversion emissions of Er{sup 3+} singly doped BiOCl microcrystals: A photon avalanche of Er{sup 3+} induced by 980?nm excitation  

SciTech Connect

Under 980?nm excitation, high multi-photon upconversion (UC) emission from the {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} (green) and {sup 4}F{sub 9/2} (red) levels of Er{sup 3+} ions were observed from Er{sup 3+} singly doped BiOCl microcrystals. These high-energy excited states were populated by a three to ten photon UC process conditionally, which depended on the pump power density and the Er{sup 3+} ion doping concentration, characterizing as a hetero-looping enhanced energy transfer avalanche UC process. UC emission lifetime and Raman analysis suggest that the unusual UC phenomena are initiated by the new and intense phonon vibration modes of BiOCl lattices due to Er{sup 3+} ions doping.

Li, Yongjin; Song, Zhiguo, E-mail: songzg@kmust.edu.cn; Li, Chen; Wan, Ronghua; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Yang, Yong; Zhou, Dacheng; Wang, Qi [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)] [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

2013-12-02

94

Three-dimensional multiphoton autofluorescence spectral imaging of live tissues  

NASA Astrophysics Data System (ADS)

We combined a homebuilt multiphoton microscope and a prism-CCD based spectrograph to develop a spectral imaging system capable of imaging deep into live tissues. The spectral images originate from the two-photon autofluorescence of the tissue and second harmonic signal from the collagen fibers. A highly penetrating near-infrared light is used to excite the endogenous fluorophores via multiphoton excitation enabling us to produce high quality images deep into the tissue. We were able to produce 100-channel (330 nm to 600 nm) autofluorescence spectral images of live skin tissues in less than 2 minutes for each xy-section. The spectral images rendered in RGB (real) colors showed green hair shafts, blue cells, and purple collagen. Analysis on the optical signal degradation with increasing depth of the collagen second-harmonic signal showed 1) exponential decay behavior of the intensity and 2) linear broadening of the spectrum. This spectral imaging system is a promising tool for both in biological applications and biomedical applications such as optical biopsy.

Palero, Jonathan A.; de Bruijn, Henriëtte S.; van der Ploeg van den Heuvel, Angélique; Sterenborg, Henricus J. C. M.; Gerritsen, Hans C.

2006-04-01

95

Non-destructive Testing by Infrared Thermography Under Random Excitation and ARMA Analysis  

NASA Astrophysics Data System (ADS)

Photothermal thermography is a non-destructive testing (NDT) method, which has many applications in the field of control and characterization of thin materials. This technique is usually implemented under CW or flash excitation. Such excitations are not adapted for control of fragile materials or for multi-frequency analysis. To allow these analyses, in this article, the use of a new control mode is proposed: infrared thermography under random excitation and auto regressive moving average analysis. First, the principle of this NDT method is presented. Then, the method is shown to permit detection, with low energy constraints, of detachments situated in mural paintings.

Bodnar, J. L.; Nicolas, J. L.; Candoré, J. C.; Detalle, V.

2012-11-01

96

Multiphoton processes: conference proceedings  

SciTech Connect

The chapters of this volume represent the invited papers delivered at the conference. They are arranged according to thermatic proximity beginning with atoms and continuing with molecules and surfaces. Section headings include multiphoton processes in atoms, field fluctuations and collisions in multiphoton process, and multiphoton processes in molecules and surfaces. Abstracts of individual items from the conference were prepared separately for the data base. (GHT)

Lambropoulos, P.; Smith, S.J. (eds.)

1984-01-01

97

Toward control of electron transfer in donor-acceptor molecules by bond-specific infrared excitation.  

PubMed

Electron transfer (ET) from donor to acceptor is often mediated by nuclear-electronic (vibronic) interactions in molecular bridges. Using an ultrafast electronic-vibrational-vibrational pulse-sequence, we demonstrate how the outcome of light-induced ET can be radically altered by mode-specific infrared (IR) excitation of vibrations that are coupled to the ET pathway. Picosecond narrow-band IR excitation of high-frequency bridge vibrations in an electronically excited covalent trans-acetylide platinum(II) donor-bridge-acceptor system in solution alters both the dynamics and the yields of competing ET pathways, completely switching a charge separation pathway off. These results offer a step toward quantum control of chemical reactivity by IR excitation. PMID:25525241

Delor, Milan; Scattergood, Paul A; Sazanovich, Igor V; Parker, Anthony W; Greetham, Gregory M; Meijer, Anthony J H M; Towrie, Michael; Weinstein, Julia A

2014-12-19

98

Multiphoton absorption in amyloid protein fibres  

NASA Astrophysics Data System (ADS)

Fibrillization of peptides leads to the formation of amyloid fibres, which, when in large aggregates, are responsible for diseases such as Alzheimer's and Parkinson's. Here, we show that amyloids have strong nonlinear optical absorption, which is not present in native non-fibrillized protein. Z-scan and pump-probe experiments indicate that insulin and lysozyme ?-amyloids, as well as ?-synuclein fibres, exhibit either two-photon, three-photon or higher multiphoton absorption processes, depending on the wavelength of light. We propose that the enhanced multiphoton absorption is due to a cooperative mechanism involving through-space dipolar coupling between excited states of aromatic amino acids densely packed in the fibrous structures. This finding will provide the opportunity to develop nonlinear optical techniques to detect and study amyloid structures and also suggests that new protein-based materials with sizable multiphoton absorption could be designed for specific applications in nanotechnology, photonics and optoelectronics.

Hanczyc, Piotr; Samoc, Marek; Norden, Bengt

2013-12-01

99

Multiphoton detachment of H-  

E-print Network

Multiphoton detachment of H- is considered. An accurate one-electron model, which reproduces precisely the known H- detachment energy and the low-energy e-H(1s) elastic-scattering phase shifts, is developed. Generalized ...

Chu, Shih-I; Laughlin, Cecil

1993-12-01

100

A Near-Infrared Transient Absorption Study of the Excited-State Dynamics of the Carotenoid Spirilloxanthin in Solution and in the LH1 Complex of Rhodospirillum rubrum  

E-print Network

A Near-Infrared Transient Absorption Study of the Excited-State Dynamics of the Carotenoid rubrum were studied by near-infrared ultrafast transient absorption spectroscopy. Global analysis), does not exhibit detectable spectral features in the near-infrared region. Introduction The excited

van Stokkum, Ivo

101

New multimodal multiphoton imaging and spectroscopy apparatus for dermatology  

NASA Astrophysics Data System (ADS)

We present the construction of a new multimodal, multiphoton spectroscopic and imaging instrument for in vivo patient use. Utilizing a tunable femtosecond laser, we are able to simultaneously acquire two-photon excited fluorescence, second harmonic generation, and confocal reflectance images at half video rate, while concurrently acquiring two-photon excited fluorescence and second harmonic generation spectra.

Yu, Yingqiu; Lee, Anthony; Wang, Hequn; Zhao, Jianhua; Tang, Shuo; Lui, Harvey; McLean, David I.; Zeng, Haishan

2010-02-01

102

Assessing and benchmarking multiphoton microscopes for biologists.  

PubMed

Multiphoton microscopy has become staple tool for tracking cells within tissues and organs due to superior depth of penetration, low excitation volumes, and reduced phototoxicity. Many factors, ranging from laser pulse width to relay optics to detectors and electronics, contribute to the overall ability of these microscopes to excite and detect fluorescence deep within tissues. However, we have found that there are few standard ways already described in the literature to distinguish between microscopes or to benchmark existing microscopes to measure the overall quality and efficiency of these instruments. Here, we discuss some simple parameters and methods that can either be used within a multiphoton facility or by a prospective purchaser to benchmark performance. This can both assist in identifying decay in microscope performance and in choosing features of a scope that are suited to experimental needs. PMID:24974026

Corbin, Kaitlin; Pinkard, Henry; Peck, Sebastian; Beemiller, Peter; Krummel, Matthew F

2014-01-01

103

Application of liposome-encapsulated ceramic phoshpors for cancer cell imaging under near infrared excitation  

NASA Astrophysics Data System (ADS)

Bioimaging with fluorescent probes is used as an invaluable tool in a biomedical field both in vivo and in vitro. However, organic dyes have some problems such as photo-breaching and cytotoxicity due to short wavelength with high quantum energy. Recently, a new approach using rare-earth-doped ceramic nanophosphors (RED-CNP) shows that fluorescence from RED-CNP in both visible (upconversion) and near infrared (NIR) wavelength region under NIR excitation is available for bioimaging. In order to efficiently introduce the RED-CNP into cancer cells, in this study we have developed a lipid nano-particles of liposome-encapsulated erbium (Er) ion-doped Y2O3 (lipo-Y2O3). Cationic lipo-Y2O3 could clearly visualize the intracellular region of human hepatocellular carcinoma Huh-7 cells by a fluorescence microscope measurements equipped with near-infrared excitation source scanning. The results imply that the lipo-Y2O3 would potentially be useful material for imaging of cancer cells. The embedded Y2O3 in the liposome having cancer-specific ligands and/or antibodies on its surface should have a great potential for cancer cell imaging in general in living subjects.

Akiyama, Hirotada; Tokuzen, Kimikazu; Otsuka, Hiroko; Soga, Kohei; Tashiro, Fumio

2010-06-01

104

Multiphoton ionization of uranium hexafluoride  

NASA Astrophysics Data System (ADS)

Multiphoton ionization (MPI) time-of-flight mass spectroscopy (TOFMS) and photoelectron spectroscopy (PES) studies of UF6 are reported using focused light from the Nd:YAG laser fundamental (?=1064 nm) and its harmonics (?=532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UF+x fragment ions, even at the lowest laser power densities at which signal could be detected. In general, the doubly charged uranium ion (U2+) intensity is much greater than that of the singly charged uranium ion (U+). For the case of the tunable dye laser experiments, the Un+ (n=1-4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The MPI-PES studies reveal only very slow electrons (?0.5 eV) for all wavelengths investigated. The dominance of the U2+ ion, the absence or very small intensities of UF+x (x=1-3) fragments, the unstructured wavelength dependence, and the preponderance of slow electrons all indicate that mechanisms may exist other than ionization of bare U atoms following the stepwise photodissociation of F atoms from the parent molecule. The data also argue against stepwise photodissociation of UF+x (x=5,6) ions. Neither of the traditional MPI mechanisms (``neutral ladder'' or the ``ionic ladder'') are believed to adequately describe the ionization phenomena observed. We propose that the multiphoton excitation of UF6 under these experimental conditions results in a highly excited molecule, superexcited UF6**. The excitation of highly excited UF6** is proposed to be facilitated by the well known ``giant resonance,'' whose energy level lies in the range of 12-14 eV above that of ground state UF6. The highly excited molecule then primarily dissociates, via multiple channels, into Un+, UF+x, fluorine atoms, and ``slow'' electrons, although dissociation into F- ions is not ruled out.

Armstrong, D. P.; Harkins, D. A.; Compton, R. N.; Ding, D.

1994-01-01

105

Spectroscopic analysis of keratin endogenous signal for skin multiphoton microscopy.  

PubMed

We recorded one-photon excited fluorescence (1PEF) and two-photon excited fluorescence (2PEF) spectra of purified keratin from human epidermis, and determined the action cross section of this endogenous chromophore. We used this spectroscopic analysis to analyse multiphoton images of skin biopsies and assign the intrinsic fluorescence signals in the epidermis. We observed a good agreement between in situ and in vitro 2PEF spectra of keratin. This study provides a comprehensive characterization of the 2PEF signal of the keratins from the epidermis, and will be of practical interest for multiphoton imaging of the skin. PMID:19498639

Pena, A; Strupler, M; Boulesteix, T; Schanne-Klein, M

2005-08-01

106

Spectroscopic analysis of keratin endogenous signal for skin multiphoton microscopy  

NASA Astrophysics Data System (ADS)

We recorded one-photon excited fluorescence (1PEF) and two-photon excited fluorescence (2PEF) spectra of purified keratin from human epidermis, and determined the action cross section of this endogenous chromophore. We used this spectroscopic analysis to analyse multiphoton images of skin biopsies and assign the intrinsic fluorescence signals in the epidermis. We observed a good agreement between in situ and in vitro 2PEF spectra of keratin. This study provides a comprehensive characterization of the 2PEF signal of the keratins from the epidermis, and will be of practical interest for multiphoton imaging of the skin.

Pena, A.-M.; Strupler, M.; Boulesteix, T.; Schanne-Klein, M.-C.

2005-08-01

107

Identification of glucosinolates in capers by LC-ESI-hybrid linear ion trap with Fourier transform ion cyclotron resonance mass spectrometry (LC-ESI-LTQ-FTICR MS) and infrared multiphoton dissociation.  

PubMed

An liquid chromatography-mass spectrometry method using electrospray ionization in negative ion mode coupled with a hybrid quadrupole linear ion trap and Fourier transform ion cyclotron resonance (FTICR) mass spectrometer was applied to characterize of intact glucosinolates (GLSs) in crude sample extracts of wild bud flowers of Capparis spinosa (Capparis species, family Capparaceae). Structural information of GLSs was obtained upon precursor ions' isolation within the FTICR trapping cell and subsequent fragmentation induced by infrared multiphoton dissociation (IRMPD). Such a fragmentation was found very useful in terms of chemical identification of all precursor ions [M-H](-) including sulfur-rich GLSs reported here for the first time. Along with most common GLSs already found in capers such as glucocapparin, isopropyl/n-propyl-GLS, mercapto-glucocapparin, and two indolic GLS, i.e., 4-hydroxyglucobrassicin and glucobrassicin, the occurrence of the uncommon glycinyl-glucocapparin as well as two sulfur-rich GLSs is reported. IRMPD showed an increased selectivity towards disulfide bond cleavages with thiol migration, suggesting the side chain structure of non-targeted compounds, i.e., disulfanyl-glucocapparin and trisulfanyl-glucocapparin. Glucocapparin [2.05?±?0.25?mg/g, dry weight (dw)] was the most abundant GLS, followed by glucobrassicin (232?±?18?µg/g, dw) and 4-hydroxyglucobrassicin (89?±?12?µg/g, dw). All other compounds were present at very low content ranging from 0.5 to 1.5?µg/g dw. PMID:22972784

Bianco, Giuliana; Lelario, Filomena; Battista, Fabio Giuseppe; Bufo, Sabino A; Cataldi, Tommaso R I

2012-09-01

108

High contrast in vivo bioimaging using multiphoton upconversion in novel rare-earth-doped fluoride upconversion nanoparticles  

NASA Astrophysics Data System (ADS)

Upconversion in rare-earth ions is a sequential multiphoton process that efficiently converts two or more low-energy photons, which are generally near infrared (NIR) light, to produce anti-Stokes emission of a higher energy photon (e.g., NIR, visible, ultraviolet) using continuous-wave (cw) diode laser excitation. Here, we show the engineering of novel, efficient, and biocompatible NIRin-to-NIRout upconversion nanoparticles for biomedical imaging with both excitation and emission being within the "optical transparency window" of tissues. The small animal whole-body imaging with exceptional contrast (signal-to-noise ratio of 310) was shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles. An imaging depth as deep as 3.2-cm was successfully demonstrated using thick animal tissue (pork) under cw laser excitation at 980 nm.

Chen, Guanying; Yang, Chunhui; Prasad, Paras N.

2013-02-01

109

Gene inactivation by multiphoton-targeted photochemistry  

PubMed Central

Multiphoton-targeted photochemistry was used to selectively inactivate the expression of genes in vertebrate cells. A membrane permeable DNA-associating vital dye, ethidium bromide monoacetate (visible wavelength single photon absorption peak at 530 nm) was used to photosensitize chromosomes in dividing cells. A 100-ps infrared laser beam operating at 1.06 microns was focused onto a selected region of a mitotic chromosome corresponding to the sites of the nucleolar (ribosomal) genes. Individual cells followed through mitosis demonstrated a reduction in the number of nucleoli formed in daughter cells that corresponded to the number of nucleolar genes sites irradiated. These results demonstrate the ability to selectively manipulate genes by using the focal point specificity characteristic of multiphoton microscopy. This technique should have wide biotechnology applications both in vitro and in vivo. PMID:10944219

Berns, Michael W.; Wang, Zifu; Dunn, Andrew; Wallace, Vincent; Venugopalan, Vasan

2000-01-01

110

Highly excited symmetry-breaking infrared and THz transitions in methanol-D 1  

NASA Astrophysics Data System (ADS)

In this paper, symmetry-breaking transitions have been identified in the Fourier transform infrared (FTIR) and Terra Hertz (THz) fast scan spectra of asymmetrically deuterated methanol CH 2DOH involving three quanta of the lowest lying vibrational state ( ?1). These transitions have an upper state belonging to highly excited torsional state with the torsional quantum number v=11 (e 5) (with the axial component of total rotational angular momentum K=5 and 6) in the Internal Axis Method (IAM) formalism developed by Quade and his co-workers [J. Mol. Spectrosc. 146 (1991) 238; J. Mol. Spectrosc. 146 (1991) 252], which was later extended by Mukhopadhyay [Spectrochim. Acta A 53 (1997) 2457; Spectrochim. Acta A 53 (1997) 1947] to include highly excited torsional-rotational states. The originating lower states belong to the o 1 ( v=3) with K=4 and 5. In analogy with pure methanol these transitions terminate to the third excited torsional state, which has very small torsional matrix elements to be observable in normal FTIR spectra. The location of the e 5 states suggests that the calculated energy levels using the parameters of Liu and Quade [J. Mol. Spectrosc. 146 (1991) 252] are reasonable and very helpful to assign such highly excited transitions, considering that their studies include low angular momentum states. In addition the very existence of these transitions proves that the matrix elements calculated by Mukhopadhyay [Spectrochim. Acta A 53 (1997) 1947] are very useful and dependable. Thus they represent a valuable tool for entangling the complex spectrum of this asymmetrically deuterated methanol. In order to provide confirmatory evidence the THz spectra obtained using the Fast Scanning Submillimeter Spectroscopy Technique (FASSST) at the Ohio State University [Rev. Instr. 68 (1997) 1675; Anal. Chem. 70 (1998) 719A] were searched for the ground state transitions that can be calculated precisely from IR combination relations. All the transitions that can be predicted with K=4 and 5 in the o 1 states are indeed identified in the FASSST spectrum. To our knowledge this is the first reported work involving direct transitions to such highly excited torsional state of CH 2DOH. This work will enable the determination of higher order barrier terms and provide enough understanding of the energy levels for the identification of many unidentified transitions. To our knowledge, this is the first time such high frequency symmetry-breaking transitions have been observed in asymmetrically deuterated methanol.

Mukhopadhyay, Indranath

2004-06-01

111

Clinical multiphoton endoscopy with FLIM capability  

NASA Astrophysics Data System (ADS)

Multiphoton endoscopy can be applied for intra-corporeal imaging as well as to examine otherwise hard-to-access tissue areas like chronic wounds. Using high-NA (NA = 0.8) gradient-index (GRIN) lens-based endoscopes with a diameter of 1.4 mm and effective lengths of 7 mm and 20 mm, respectively, two-photon excitation of endogenous fluorophores and second-harmonic generation (SHG) is used for multimodal in vivo imaging of human skin. A further imaging modality is fluorescence lifetime imaging (FLIM) which allows functional imaging to investigate the healing mechanism of chronic wounds and the corresponding cell metabolism. We performed first in vivo measurements using FLIM endoscopy with the medically-certified multiphoton tomograph MPTflex® in combination with a computer-controlled motorized scan head and a GRIN-lens endoscope.

Weinigel, Martin; Breunig, Hans Georg; Fischer, Peter; Kellner-Höfer, Marcel; Bückle, Rainer; König, Karsten

2013-02-01

112

Highly Emitting Near-Infrared Lanthanide “Encapsulated Sandwich” Metallacrown Complexes with Excitation Shifted Toward Lower Energy  

PubMed Central

Near-infrared (NIR) luminescent lanthanide complexes hold great promise for practical applications, as their optical properties have several complementary advantages over organic fluorophores and semiconductor nanoparticles. The fundamental challenge for lanthanide luminescence is their sensitization through suitable chromophores. The use of the metallacrown (MC) motif is an innovative strategy to arrange several organic sensitizers at a well-controlled distance from a lanthanide cation. Herein we report a series of lanthanide “encapsulated sandwich” MC complexes of the form Ln3+[12-MCZn(II),quinHA-4]2[24-MCZn(II),quinHA-8] (Ln3+[Zn(II)MCquinHA]) in which the MC framework is formed by the self-assembly of Zn2+ ions and tetradentate chromophoric ligands based on quinaldichydroxamic acid (quinHA). A first-generation of luminescent MCs was presented previously but was limited due to excitation wavelengths in the UV. We report here that through the design of the chromophore of the MC assembly, we have significantly shifted the absorption wavelength toward lower energy (450 nm). In addition to this near-visible inter- and/or intraligand charge transfer absorption, Ln3+[Zn(II)MCquinHA] exhibits remarkably high quantum yields, long luminescence lifetimes (CD3OD; Yb3+, QLnL = 2.88(2)%, ?obs = 150.7(2) ?s; Nd3+, QLnL = 1.35(1)%, ?obs = 4.11(3) ?s; Er3+, QLnL = 3.60(6)·10–2%, ?obs = 11.40(3) ?s), and excellent photostability. Quantum yields of Nd3+ and Er3+ MCs in the solid state and in deuterated solvents, upon excitation at low energy, are the highest values among NIR-emitting lanthanide complexes containing C–H bonds. The versatility of the MC strategy allows modifications in the excitation wavelength and absorptivity through the appropriate design of the ligand sensitizer, providing a highly efficient platform with tunable properties. PMID:24432702

2015-01-01

113

Highly emitting near-infrared lanthanide "encapsulated sandwich" metallacrown complexes with excitation shifted toward lower energy.  

PubMed

Near-infrared (NIR) luminescent lanthanide complexes hold great promise for practical applications, as their optical properties have several complementary advantages over organic fluorophores and semiconductor nanoparticles. The fundamental challenge for lanthanide luminescence is their sensitization through suitable chromophores. The use of the metallacrown (MC) motif is an innovative strategy to arrange several organic sensitizers at a well-controlled distance from a lanthanide cation. Herein we report a series of lanthanide “encapsulated sandwich” MC complexes of the form Ln3+ [12-MC(Zn(II),quinHA)-4]2[24-MC(Zn(II),quinHA)-8] (Ln3+ [Zn(II)MC(quinHA)]) in which the MC framework is formed by the self-assembly of Zn2+ ions and tetradentate chromophoric ligands based on quinaldichydroxamic acid (quinHA). A first-generation of luminescent MCs was presented previously but was limited due to excitation wavelengths in the UV. We report here that through the design of the chromophore of the MC assembly, we have significantly shifted the absorption wavelength toward lower energy (450 nm). In addition to this near-visible inter- and/or intraligand charge transfer absorption, Ln3+ [Zn(II)MC(quinHA)] exhibits remarkably high quantum yields, long luminescence lifetimes (CD3OD; Yb3+, QLn(L) = 2.88(2)%, ?obs = 150.7(2) ?s; Nd3+, QLn(L) = 1.35(1)%, ?obs = 4.11(3) ?s; Er3+, QLn(L) = 3.60(6)·10–2%, ?obs = 11.40(3) ?s), and excellent photostability. Quantum yields of Nd3+ and Er3+ MCs in the solid state and in deuterated solvents, upon excitation at low energy, are the highest values among NIR-emitting lanthanide complexes containing C–H bonds. The versatility of the MC strategy allows modifications in the excitation wavelength and absorptivity through the appropriate design of the ligand sensitizer, providing a highly efficient platform with tunable properties. PMID:24432702

Trivedi, Evan R; Eliseeva, Svetlana V; Jankolovits, Joseph; Olmstead, Marilyn M; Petoud, Stéphane; Pecoraro, Vincent L

2014-01-29

114

Optical multiphoton lattices  

SciTech Connect

We propose a scheme that allows us to Fourier-synthesize arbitrarily shaped periodic potentials for atoms. The method is based on the dispersion connected with higher order multiphoton Raman processes, where a suitable combination of laser frequencies eliminates unwanted standing wave effects. Future application of the scheme could range from blazed atomic beam splitters up to atomic quantum ratchets.

Weitz, Martin; Cennini, Giovanni; Ritt, Gunnar; Geckeler, Carsten [Physikalisches Institut der Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany)

2004-10-01

115

Characterizing lamina propria of human gastric mucosa by multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Lamina propria (LP) of gastric mucosa plays an important role in progression of gastric cancer because of the site at where inflammatory reactions occur. Multiphoton imaging has been recently employed for microscopic examination of intact tissue. In this paper, using multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG), high resolution multiphoton microscopic images of lamina propria (LP) are obtained in normal human gastric mucosa at excitation wavelength ?ex = 800 nm. The main source of tissue TPEF originated from the cells of gastric glands, and loose connective tissue, collagen, produced SHG signals. Our results demonstrated that MPM can be effective for characterizing the microstructure of LP in human gastric mucosa. The findings will be helpful for diagnosing and staging early gastric cancer in the clinics.

Liu, Y. C.; Yang, H. Q.; Chen, G.; Zhuo, S. M.; Chen, J. X.; Yan, J.

2011-01-01

116

Post conductive keratoplasty visualization of rabbit cornea by multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Conductive keratoplasty (CK) is a new refractive surgery for presbyopia and hyperopia patients. By applying radio frequency current at the peripheral regions of cornea, collagen, the most abundant composition of corneal stroma, shrinks due to the heat generated. The shrinkage at the periphery alters the corneal architecture and achieves clearer focus for near vision. In this work we use multiphoton microscopy to observe the post surgery structure variation at both submicron resolution and over a large region within the tissue. Since collagen can be induced to generate strong second harmonic generation (SHG) signal, multiphoton excitation provide direct visualization of collagen orientation within corneal stroma. In addition, since the SHG intensity of collagen tissue deteriorates with increasing thermal damage [1-3], our methodology can be used to characterize the extent of corneal stroma damage from the CK procedure. Finally, the influence of CK on the morphology and distribution of keratocytes can also be investigated by detecting multiphoton excited autofluorescence from the cells.

Lo, Wen; Wang, Tsung-Jen; Hu, Fung-Rong; Dong, Chen-Yuan

2007-07-01

117

Studies of atmospheric molecules by multiphoton spectroscopy  

SciTech Connect

Carbon dioxide presents a great challenge to spectroscopy because of its propensity toward dissociation in all of its excited states. Multiphoton ionization spectroscopy is usually not applicable to the study of dissociating molecules because the dissociation competes effectively with ionization, resulting in no signal. We reasoned, however, that with high enough laser fluence, ionization could compete with dissociation in the longer lived states, exposing them for study from the continuous spectral background resulting from rapidly dissociating states. We describe the various spectroscopic and photophysical effects found through the multiphoton ionization and multiphoton photoelectron spectra. A recently developed variant of threshold ionization spectroscopy, usually called ZEKE, has shown a great deal of usefulness in providing the same information as traditional photoelectron spectroscopy but with higher resolution and much better signal-to-noise when using standard laboratory lasers. Threshold ionization techniques locate the states of an ion by scanning a light source across the ionization continuum of a neutral and somehow detecting when electrons are produced with no kinetic energy. We chose to develop our capabilities in threshold ionization spectroscopy using aromatic molecules because of their importance and because their electronic structure allows a pump-probe type of excitation scheme which avoids the use of vacuum ultraviolet laser beams. Among aromatics, the azines are noted for their small S{sub 1}-T{sub 1} energy gap which give them unique and interesting photophysical properties. We have continued our work on the multiphoton spectrum of metastable nitrogen produced by an electric discharge in supersonic beam. We have been able to assign more of the lines and simulated their rotational structure but many peaks remain unassigned.

Johnson, P.M.

1991-10-01

118

Non Destructive Testing by active infrared thermography coupled with shearography under same optical heat excitation  

NASA Astrophysics Data System (ADS)

As infrastructures are aging, the evaluation of their health is becoming crucial. To do so, numerous Non Destructive Testing (NDT) methods are available. Among them, thermal shearography and active infrared thermography represent two full field and contactless methods for surface inspection. The synchronized use of both methods presents multiples advantages. Most importantly, both NDT are based on different material properties. Thermography depend on the thermal properties and shearography on the mechanical properties. The cross-correlation of both methods result in a more accurate and exact detection of the defects. For real site application, the simultaneous use of both methods is simplified due to the fact that the excitation method (thermal) is the same. Active infrared thermography is the measure of the temperature by an infrared camera of a surface subjected to heat flux. Observation of the variation of temperature in function of time reveal the presence of defects. On the other hand, shearography is a measure of out-of-plane surface displacement. This displacement is caused by the application of a strain on the surface which (in our case) take the form of a temperature gradient inducing a thermal stress To measure the resulting out-of-plane displacement, shearography exploit the relation between the phase difference and the optical path length. The phase difference is measured by the observation of the interference between two coherent light beam projected on the surface. This interference is due to change in optical path length as the surface is deformed [1]. A series of experimentation have been conducted in laboratory with various sample of concrete reinforced with CFRP materials. Results obtained reveal that with both methods it was possible to detect defects in the gluing. An infrared lamp radiating was used as the active heat source. This is necessary if measurements with shearography are to be made during the heating process. A heating lamp in the visible spectrum would hinder the projected light beam since a laser with wavelength of 532 nm was used as the coherent light source. Experimentations were successful, but only with mitigated efficiency for shearography [2]. The thermal response was the fastest and it was possible to fully locate all defects. For shearography, the available equipment forced us to restrict the area of observation to only one defect at a time (roughly 100 cm²). Numerical models were designed based on the multiple sample tested in the experimental step of the study. Using the COMSOL© finite elements modeling software, numerous simulations yielded results in accordance with experimental data. Different types of defect could be modeled and showed that both shearography and thermography have different sensibility in function of the nature of the defect. Furthermore, analysis of the simulated results demonstrated a relation between the contrast evolution of the temperature and displacement field. In the near future, we expect to make several improvement to our experimental setup. As for the numerical model, some small disparities between the theoretical and experimental results still remain to be addressed. The numerical model could be improved but to do so it requires to raise the shearographic measurements sampling rate close to the one used for infrared thermography. Once this issue will be resolved, it will be possible to use experimental data to refine the numerical model. So, accurate models will be helpful to optimize the overall efficiency of the coupling of thermal shearography and active infrared thermography for in situ NDT application. References [1] Y.Y. Hung, C.Y. Liand, Image-shearing camera for direct measurement of surface strains, Applied Optics, Vol. 18, n°7, pages 1046-1051, 1979 [2] L-D. Théroux, J. Dumoulin, X. Maldague, Square heating applied to shearography and active infrared thermography measurements coupling: form feasibility test in laboratory to numerical study of pultruded CFRP plates glued on concrete specimen, STRAIN journal, in press

Theroux, Louis-Daniel; Dumoulin, Jean; Maldague, Xavier

2014-05-01

119

Dynamic particle tracking via temporal focusing multiphoton microscopy with astigmatism imaging.  

PubMed

A three-dimensional (3D) single fluorescent particle tracking strategy based on temporal focusing multiphoton excitation microscopy (TFMPEM) combined with astigmatism imaging is proposed for delivering nanoscale-level axial information that reveals 3D trajectories of single fluorospheres in the axially-resolved multiphoton excitation volume without z-axis scanning. Whereas other scanning spatial focusing multiphoton excitation schemes induce optical trapping interference, temporal focusing multiphoton excitation produces widefield illumination with minimum optical trapping force on the fluorospheres. Currently, the lateral and axial positioning resolutions of the dynamic particle tracking approach are about 14 nm and 21 nm in standard deviation, respectively. Furthermore, the motion behavior and diffusion coefficients of fluorospheres in glycerol solutions with different concentrations are dynamically measured at a frame rate up to 100 Hz. This TFMPEM with astigmatism imaging holds great promise for exploring dynamic molecular behavior deep inside biotissues via its superior penetration, reduced trapping effect, fast frame rate, and nanoscale-level positioning. PMID:25401879

Lien, Chi-Hsiang; Lin, Chun-Yu; Chen, Shean-Jen; Chien, Fan-Ching

2014-11-01

120

Two-photon-excited upconversion luminescence of Mn2+-doped germanate glass by infrared femtosecond laser irradiation  

NASA Astrophysics Data System (ADS)

We report on the upconversion luminescence of transition metal Mn ions doped germanate glass exited by an infrared femtosecond laser at room temperature. The luminescent spectra exhibited that the upconversion luminescence originates from the Mn2+ ions. The dependence of the fluorescence intensity on the pump power reveals that a two-photon excitation process dominates in the conversion of infrared radiation to the visible emission. It is suggested that the simultaneous absorption of two infrared photons produces the population of upper excited states, which leads to the characteristic visible emission. Furthermore, we observed that the photo-oxidation of Mn2+ ions to Mn3+ ions by measuring the absorption spectra of the Mn ions doped germanate glass before and after femtosecond laser irradiation.

Zhang, Yang; Li, Pengfei; Wang, Chengwei; Bao, Zongjie; Zhao, Quan-Zhong

2014-09-01

121

Extended infrared line emission excited by starburst and Seyfert activity in NGC 3256 and NGC 4945  

NASA Astrophysics Data System (ADS)

We present visible and infrared images, 1.5 to 2.3 micrometer infrared spectra and (Fe II) 1.64 micrometer, H2 (1 - 0) S(1) 2.121 micrometer, and Brgamma 2.165 micrometer infrared line contour maps obtained to investigate the nature of the activity and the origin of the infrared line emission in two relatively nearby infrared luminous galaxies. NGC 3256 is a merging system exhibiting starburst activity over a region several kpc across and a high infrared luminosity of approximately 3 x 1011 solar luminosity. A specific search for (Si VI) 1.96 micrometer coronal line emission from a possibly visually obscured Seyfert nucleus proved negative. Extremely high star-formation and SN rates of approximately 20 solar mass/year and approximately 1.5/year, respectively, however, are estimated using the observed integrated Brgamma line luminosites and He I 2.06 micrometer/Brgamma ratios together with an existing starburst model. At this rate, the injection energy associated with SN explosions alone could account for the observed (Fe II) 1.64 micrometer and H2(1 - 0)S(1) line luminosities. NGC 4945 is an almost edge-on spiral with an order of magnitude lower infrared luminosity which is powered by both a approximately 400 pc size starburst and a visually obscured Seyfert nucleus which is a variable source of hard X-ray emission and could substantially contribute to the total luminosity. Its star formation efficiency is higher than in NGC 3256 whereas its luminosity and star formation and SN rates of (approximately 0.4 solar mass/year and approximately 0.05/year are much lower although still adequate to account for the excitation of the observed (Fe II) 1.64 micrometer and H2(1 - 0)S(1) lines. Based on previous survey work, however, the large integrated H2(1 - 0)S(1)/Brgamma ratio observed in this galaxy is also indicative of the presence of a Seyfert nucleus. Maps of the Brgamma, (Fe II), and H2 (1 - 0)S(1) line emission reveal significantly different spatial distributions in the two galaxies. In NGC 3256 the emission extends over a region approximately 4 kpc across and shows similar (Fe II) and Brgamma morphologies, whereas the H2 (1 - 0)S(1) emission does not correlate in detail with either. In particular, it is less peaked on the nucleus and traces a spiral arm and embedded source to the south of the nucleus. This source is also prominent in our K' (2.1 micrometer) image but totally obscured by dust in the visible and is probably the nucleus of the merging companion. Additional evidence that the merger is not yet complete is also provided by the fact that the light distribution in the K' image does not correspond to that expected of a relaxed system. In NGC 4945 the Brgamma emission is largely confined to a approximately 380 pc diameter and less than or equal to 190 pc thick disk in the plane of the galaxy whereas both the (Fe II) 1.64 micrometer and H2 (1 - 0)S(1) line emission extends over the full extent of the molecular complex which is a factor of 2 larger perpendicular to the plane. This morphology is consistent with additional excitation by an embedded active galactic nucleus and/or a starburst driven superwind. The similarity of the observed (Fe II) and H2 intensity profiles perpendicular to the plane suggests a common excitation mechanism for the 'excess' emission which we propose can be attributed to partial ionization and heating of molecular gas respectively by X-rays from the nuclear source. The overall conclusion of this study is that NGC 4945 is probably at an advanced stage of its evolution from a starburst to a Seyfert galaxy whereas there is no evidence that such an evolution is occurring yet in the considerably more luminous, merging system, NGC 3256.

Moorwood, A. F. M.; Oliva, E.

1994-07-01

122

Spectroscopic analysis of skin intrinsic signals for multiphoton microscopy  

Microsoft Academic Search

We recorded multiphoton images of human skin biopsies using endogenous sources of nonlinear optical signals. We detected simultaneously two-photon excited fluorescence (2PEF) from intrinsic fluorophores and second harmonic generation (SHG) from collagen. We observed SHG from fibrillar collagens in the dermis, whereas no SHG was detectable from the non fibrillar type IV collagen in the basal laminae. We compared these

Ana-Maria Pena; Mathias Strupler; Thierry Boulesteix; Karim Senni; Gaston Godeau; Emmanuel Beaurepaire; Marie-Claire Schanne-Klein

2006-01-01

123

Adaptive optics multiphoton microscopy  

NASA Astrophysics Data System (ADS)

We have developed an adaptive optics multiphoton microscope. The multiphoton imaging system combines an ultrafast high-power laser, a scanning unit, a motorized Z-scan device and a photon-counting detector. The adaptive optics module is composed of a Hartmann-Shack wavefront sensor and a MEMS deformable mirror. The impact of compensating the aberrations of the laser beam is shown in a number of biological and non-biological samples. As examples, nonlinear fluorescence and second harmonic generation images of non-stained ex-vivo ocular tissues are compared with and without adaptive optics. The correction of the beam's aberrations increases both contrast and resolution in the non-linear microscope images.

Gualda, Emilio J.; Bueno, Juan M.; Artal, Pablo

2010-02-01

124

An Interplay Between Infrared Multiphoton Dissociation Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry and Density Functional Theory Computations in the Characterization of a Tripodal Quinolin-8-Olate Gd(III) Complex  

NASA Astrophysics Data System (ADS)

A new hexadentate, tripodal 8-hydroxyquinoline based ligand (QH3) and its gadolinium(III) tris-chelated (GdQ) complex with hemicage structure was investigated by using high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICRMS). The protonated adduct of the free ligand and its hemicage tripodal Gd(III) complex, [GdQ + H]+, were first observed in experiments of electrospray ionization (ESI) with a linear ion trap (LTQ) mass spectrometer and further investigated by using high resolution FTICRMS. Gas-phase dissociation of the protonated Gd(III) complex, by infrared multiphoton dissociation (IRMPD) FTICR MS, demonstrated a fragmentation pattern with six main product cluster ions labeled as [Fn]+ ( n = 1 up to 6). These product ions suggest the elimination of 7-amino-alkyl or 7-alkyl chains of the hemicage moiety. High resolution MS conditions allowed the elucidation of the fragmentation pattern and product ion structures along with the determination, among the isotopic pattern of Gd, of the chemical compositions of closely related species, which differ in terms of hydrogen content. Among the Gd six naturally stable isotopes, 158Gd is the most abundant, and its peak within each cluster was used as a reference for distinguishing each product ions. Computational DFT investigations were applied to give support to some hypothesis of fragmentation pathways, which could not have been easily justified on the basis of the experimental work. Furthermore, computational studies suggested the coordination geometry of the protonated parent complex and the five- and four-coordinated complexes, which derive from its fragmentation. Furthermore, experimental and computational evidences were collected about the octet spin state of the parent compound.

De Bonis, Margherita; Bianco, Giuliana; Amati, Mario; Belviso, Sandra; Cataldi, Tommaso R. I.; Lelj, Francesco

2013-04-01

125

An interplay between infrared multiphoton dissociation Fourier-transform ion cyclotron resonance mass spectrometry and density functional theory computations in the characterization of a tripodal quinolin-8-olate Gd(III) complex.  

PubMed

A new hexadentate, tripodal 8-hydroxyquinoline based ligand (QH3) and its gadolinium(III) tris-chelated (GdQ) complex with hemicage structure was investigated by using high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICRMS). The protonated adduct of the free ligand and its hemicage tripodal Gd(III) complex, [GdQ + H](+), were first observed in experiments of electrospray ionization (ESI) with a linear ion trap (LTQ) mass spectrometer and further investigated by using high resolution FTICRMS. Gas-phase dissociation of the protonated Gd(III) complex, by infrared multiphoton dissociation (IRMPD) FTICR MS, demonstrated a fragmentation pattern with six main product cluster ions labeled as [Fn](+) (n = 1 up to 6). These product ions suggest the elimination of 7-amino-alkyl or 7-alkyl chains of the hemicage moiety. High resolution MS conditions allowed the elucidation of the fragmentation pattern and product ion structures along with the determination, among the isotopic pattern of Gd, of the chemical compositions of closely related species, which differ in terms of hydrogen content. Among the Gd six naturally stable isotopes, (158)Gd is the most abundant, and its peak within each cluster was used as a reference for distinguishing each product ions. Computational DFT investigations were applied to give support to some hypothesis of fragmentation pathways, which could not have been easily justified on the basis of the experimental work. Furthermore, computational studies suggested the coordination geometry of the protonated parent complex and the five- and four-coordinated complexes, which derive from its fragmentation. Furthermore, experimental and computational evidences were collected about the octet spin state of the parent compound. PMID:23436232

De Bonis, Margherita; Bianco, Giuliana; Amati, Mario; Belviso, Sandra; Cataldi, Tommaso R I; Lelj, Francesco

2013-04-01

126

Investigating excited state dynamics of salinixanthin and xanthorhodopsin in the near-infrared.  

PubMed

Excited state dynamics of native Xanthorhodopsin (XR), of an XR sample with a reduced prosthetic group, and of the associated Carotenoid (CAR) salinixanthin (SX) in ethanol were investigated by hyperspectral Near Infrared (NIR) probing. Global kinetic analysis shows that: (1) unlike the transient spectra recorded in the visible, fitting of the NIR data requires only two phases of exponential spectral evolution, assigned to internal conversion from S(2) ? S(1) and from S(1) ? S(0) of the carotene. (2) The rate of the internal conversion from S(2) ? S(1) in the reduced sample is well fit with a decay time of 130 fs, significantly longer than in XR and in SX, both of which are well fit with ? ? 100 fs. This increased lifetime is consistent with a ?30% efficiency of ET from SX to retinal in XR. (3) S(1) of salinixanthin is verified to lie ?12,700 cm(-1) above the ground electronic surface, excluding its involvement in the retinal sensitization in XR. (4) The oscillator strength of the S(1) ? S(2) transition is determined to be no more than 0.16, despite its symmetry allowedness. (5) No long lived NIR absorbance decay assignable to the carotenoid S* state was detected in any of the samples. Inconsistencies concerning previously determined S(2) lifetimes and kinetic schemes used to model these data are discussed. PMID:21183996

Gdor, Itay; Zhu, Jingyi; Loevsky, Boris; Smolensky, Elena; Friedman, Noga; Sheves, Mordechai; Ruhman, Sanford

2011-03-01

127

65 nm feature sizes using visible wavelength 3-D multiphoton lithography.  

PubMed

Nanoscale features as small as 65 +/- 5 nm have been formed reproducibly by using 520 nm femtosecond pulsed excitation of a 4,4'-bis(di-n-butylamino)biphenyl chromophore to initiate crosslinking in a triacrylate blend. Dosimetry studies of the photoinduced polymerization were performed on chromophores with sizable two-photon absorption cross-sections at 520 and 730 nm. These studies show that sub-diffraction limited line widths are obtained in both cases with the lines written at 520 nm being smaller. Three-dimensional multiphoton lithography at 520 nm has been used to fabricate polymeric woodpile photonic crystal structures that show stop bands in the near-infrared spectral region. PMID:19532584

Haske, Wojciech; Chen, Vincent W; Hales, Joel M; Dong, Wenting; Barlow, Stephen; Marder, Seth R; Perry, Joseph W

2007-03-19

128

Experimental Resonance Enhanced Multiphoton Ionization (REMPI) studies of small molecules  

NASA Technical Reports Server (NTRS)

Resonance enhanced multiphoton ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of exciting opportunities for both basic and applied science. On the applied side, REMPI has great potential as an ultrasensitive, highly selective detector for trace, reactive, or transient species. On the basic side, REMPI affords an unprecedented means of exploring excited state physics and chemistry at the quantum-state-specific level. An overview of current studies of excited molecular states is given to illustrate the principles and prospects of REMPI.

Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.; Ohalloran, M. A.; Tomkins, F. S.

1987-01-01

129

Spatially and frequency-resolved monitoring of intradie capacitive coupling by heterodyne excitation infrared lock-in thermography  

NASA Astrophysics Data System (ADS)

This paper combines the infrared lock-in thermography (IR-LIT) and heterodyne excitation techniques to detect high-frequency capacitive currents due to intradie electrical coupling between microelectronic devices or more complex systems. Modulating the excitation with the heterodyne approach, we drive devices or complex systems with high frequency electrical signals in such a way that they behave as low frequency heat sources, modulating their temperature field at a frequency detectable by an IR-LIT system. This approach is analytically studied and extended to a bi-dimensional scenario, showing that the thermal information at low frequency depends on the electrical characteristics of the sample at high frequency.

León, J.; Perpiñà, X.; Altet, J.; Vellvehi, M.; Jordà, X.

2013-02-01

130

Spectroscopic analysis of keratin endogenous signal for skin multiphoton microscopy  

Microsoft Academic Search

We recorded one-photon excited fluorescence (1PEF) and two-photon excited fluorescence (2PEF) spectra of purified keratin from human epidermis, and determined the action cross section of this endogenous chromophore. We used this spectroscopic analysis to analyse multiphoton images of skin biopsies and assign the intrinsic fluorescence signals in the epidermis. We observed a good agreement between in situ and in vitro

A.-M. Pena; M. Strupler; T. Boulesteix; M.-C. Schanne-Klein

2005-01-01

131

Photosensitizer-doped conjugated polymer nanoparticles with high cross-sections for one- and two-photon excitation.  

PubMed

We report a novel nanoparticle that is promising for photodynamic therapy applications, which consists of a ?-conjugated polymer doped with a singlet oxygen photosensitizer. The nanoparticles exhibit highly efficient collection of excitation light due to the large excitation cross-section of the polymer. A quantum efficiency of singlet oxygen production of 0.5 was determined. Extraordinarily large two-photon excitation cross-sections were determined, indicating promise for near infrared multiphoton photodynamic therapy. Gel electrophoresis of DNA after near-UV irradiation in the presence of nanoparticles indicated both purine base and backbone DNA damage. PMID:21293789

Grimland, Jennifer L; Wu, Changfeng; Ramoutar, Ria R; Brumaghim, Julia L; McNeill, Jason

2011-04-01

132

Low cytotoxicity porous Nd2(SiO4)3 nanoparticles with near infrared excitation and emission  

Microsoft Academic Search

Porous Nd2(SiO4)3 nanoparticles were successfully synthesized by a controlled route. This kind of silicate nanoparticle could be excited by near-infrared (NIR) radiation (808 nm) and triggered a NIR emission (1066 nm) at room temperature. By monitoring the 1066 nm emission, the long-lived luminescent lifetime was determined to be 19.5 µs. These NIR nanoparticles with appropriate diameters (<100 nm) were suitable

Xian-Hua Zhang; Dequan Zeng; Lei Zhang; Haomiao Zhu; Guang-Hui Jin; Zhaoxiong Xie; Xueyuan Chen; Junyong Kang; Lansun Zheng

2011-01-01

133

Efficiency vs. multi-photon contribution test for quantum dots  

E-print Network

The development of linear quantum computing within integrated circuits demands high quality semiconductor single photon sources. In particular, for a reliable single photon source it is not sufficient to have a low multi-photon component, but also to possess high efficiency. We investigate the photon statistics of the emission from a single quantum dot with a method that is able to sensitively detect the trade-off between the efficiency and the multi-photon contribution. Our measurements show, that the light emitted from the quantum dot when it is resonantly excited possess a very low multi-photon content. Additionally, we demonstrated, for the first time, the non-Gaussian nature of the quantum state emitted from a single quantum dot.

Ana Predojevic; Miroslav Jezek; Tobias Huber; Harishankar Jayakumar; Thomas Kauten; Glenn S. Solomon; Radim Filip; Gregor Weihs

2014-03-19

134

Reduction of excitation light leakage to improve near-infrared fluorescence imaging for tissue surface and deep tissue imaging  

PubMed Central

Purpose: Fluorescence-enhanced optical imaging using near-infrared (NIR) light developed for in vivo molecular targeting and reporting of various diseases provides promising opportunities for diagnostic imaging. However, the measurement sensitivity of NIR fluorescence (NIRF) optical imaging systems is limited by the leakage of the strong backscattered excitation light through rejection filters. In this article, the authors present a systematic method for improving sensitivity and validating the NIRF optical imager currently used for clinical imaging of human lymphatic function. Methods: The proposed systemic method consists of an appropriate filter combination and a collimation optics adapted to an NIRF optical imager. The spectral contributions were first assessed due to the excitation light backscattered from the tissue and from non-normal-incidence of the excitation light on the optical filters used in the authors’ NIRF clinical imaging system. Then two tests were conducted to assess the system with and without the components of appropriate filters combination and collimation optics using: (1) a phantom to evaluate excitation light leakage as a function of target depth and (2) deployment in an actual human study. Results: The phantom studies demonstrate as much as two to three orders of magnitude reduction in the transmission ratio, indicating that the excitation light leakage can be reduced upon using the appropriate filter combination and collimation optics while an in vivo investigatory human study confirms improved imaging. Conclusions: The method for reducing the excitation light leakage is presented for validating collected signals for fluorescence imaging. PMID:21158309

Zhu, Banghe; Rasmussen, John C.; Lu, Yujie; Sevick-Muraca, Eva M.

2010-01-01

135

PHYSICAL REVIEW A 83, 013405 (2011) Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser  

E-print Network

) to infrared radiations (1�105 nm). With the recent development of intense and ultrashort-wavelength free-electron lasers [32­34], the study of multiphoton * zyzhou@ku.edu sichu@ku.edu processes in the high

Chu, Shih-I

136

Improvement of depth resolution on photoacoustic imaging using multiphoton absorption  

NASA Astrophysics Data System (ADS)

Commercial imaging systems, such as computed tomography and magnetic resonance imaging, are frequently used powerful tools for observing structures deep within the human body. However, they cannot precisely visualized several-tens micrometer-sized structures for lack of spatial resolution. In this presentation, we propose photoacoustic imaging using multiphoton absorption technique to generate ultrasonic waves as a means of improving depth resolution. Since the multiphoton absorption occurs at only the focus point and the employed infrared pulses deeply penetrate living tissues, it enables us to extract characteristic features of structures embedded in the living tissue. When nanosecond pulses from a 1064-nm Nd:YAG laser were focused on Rhodamine B/chloroform solution (absorption peak: 540 nm), the peak intensity of the generated photoacoustic signal was proportional to the square of the input pulse energy. This result shows that the photoacoustic signals can be induced by the two-photon absorption of infrared nanosecond pulse laser and also can be detected by a commercial low-frequency MHz transducer. Furthermore, in order to evaluate the depth resolution of multiphoton-photoacoustic imaging, we investigated the dependence of photoacoustic signal on depth position using a 1-mm-thick phantom in a water bath. We found that the depth resolution of two-photon photoacoustic imaging (1064 nm) is greater than that of one-photon photoacoustic imaging (532 nm). We conclude that evolving multiphoton-photoacoustic imaging technology renders feasible the investigation of biomedical phenomena at the deep layer in living tissue.

Yamaoka, Yoshihisa; Fujiwara, Katsuji; Takamatsu, Tetsuro

2007-07-01

137

Multiphoton ionization of barium with a tunable pulsed laser in the range 570-608 nm  

Microsoft Academic Search

Multiphoton ionization (MPI) of barium atom using an excimer-pumped pulsed dye laser has been studied in the wavelength range 570-608 nm at a laser intensity approximately 10.0 GW cm-2. Resonances in MPI were recorded by monitoring either the ions produced in the multiphoton process using a thermionic detector or fluorescence from the ions formed in their various excited states of

S G Nakhate; S A Ahmad; M A N Razvi; G D Saksena

1991-01-01

138

Multiphoton microscopy as a detection tool for photobleaching of EO materials.  

PubMed

Multi-photon microscopy operating at 1550 nm is employed as a rapid characterization tool for studying the photostability of three well-known electro-optical materials. Different nonlinear optical responses such as multi-photon excitation fluoresence, second-, and third-harmonic generation can be used as detection probes to reveal the degradation mechanisms. This technique is rapid, accurate, and can be used to study the photostability of a broad range of materials. PMID:25607044

Shahin, Shiva; Mehravar, Soroush; Gangopadhyay, Palash; Peyghambarian, Nasser; Norwood, Robert A; Kieu, Khanh

2014-12-15

139

Attosecond XUV absorption spectroscopy of doubly excited states in helium atoms dressed by a time-delayed femtosecond infrared laser  

NASA Astrophysics Data System (ADS)

In the present paper, we investigate the time-resolved transient absorption spectroscopy of doubly excited states of helium atoms by solving the time-dependent two-electron Schrödinger equation numerically based on a one-dimensional model. The helium atoms are subjected to an extreme ultraviolet (XUV) attosecond pulse and a time-delayed infrared (IR) few-cycle laser pulse. A superposition of doubly excited states populated by the XUV pulse is identified, which interferes with the direct ionization pathway leading to Fano resonance profiles in the photoabsorption spectrum. In the presence of an IR laser, however, the Fano line profiles are strongly modified: A shifting, splitting, and broadening of the original absorption lines is observed when the XUV attosecond pulse and infrared few-cycle laser pulse overlap in time, which is in good agreement with recent experimental results. At certain time delays, we observe symmetric Lorentz, inverted Fano profiles, and even negative absorption cross sections indicating that the XUV light can be amplified during the interaction with atoms. We further prove that the above pictures are general for different doubly excited states by suitably varying the frequency of the IR field to coherently couple the corresponding states.

Yang, Z. Q.; Ye, D. F.; Ding, Thomas; Pfeifer, Thomas; Fu, L. B.

2015-01-01

140

Infrared  

NASA Astrophysics Data System (ADS)

'Infrared' is a very wide field in physics and the natural sciences which has evolved enormously in recent decades. It all started in 1800 with Friedrich Wilhelm Herschel's discovery of infrared (IR) radiation within the spectrum of the Sun. Thereafter a few important milestones towards widespread use of IR were the quantitative description of the laws of blackbody radiation by Max Planck in 1900; the application of quantum mechanics to understand the rotational-vibrational spectra of molecules starting in the first half of the 20th century; and the revolution in source and detector technologies due to micro-technological breakthroughs towards the end of the 20th century. This has led to much high-quality and sophisticated equipment in terms of detectors, sources and instruments in the IR spectral range, with a multitude of different applications in science and technology. This special issue tries to focus on a few aspects of the astonishing variety of different disciplines, techniques and applications concerning the general topic of infrared radiation. Part of the content is based upon an interdisciplinary international conference on the topic held in 2012 in Bad Honnef, Germany. It is hoped that the information provided here may be useful for teaching the general topic of electromagnetic radiation in the IR spectral range in advanced university courses for postgraduate students. In the most general terms, the infrared spectral range is defined to extend from wavelengths of 780 nm (upper range of the VIS spectral range) up to wavelengths of 1 mm (lower end of the microwave range). Various definitions of near, middle and far infrared or thermal infrared, and lately terahertz frequencies, are used, which all fall in this range. These special definitions often depend on the scientific field of research. Unfortunately, many of these fields seem to have developed independently from neighbouring disciplines, although they deal with very similar topics in respect of the underlying physics. There are now at least six different disciplines that deal with infrared radiation in one form or another, and in one or several different spectral portions of the whole IR range. These are spectroscopy, astronomy, thermal imaging, detector and source development and metrology, as well the field of optical data transmission. Scientists working in these fields range from chemists and astronomers through to physicists and even photographers. This issue presents examples from some of these fields. All the papers—though some of them deal with fundamental or applied research—include interesting elements that make them directly applicable to university-level teaching at the graduate or postgraduate level. Source (e.g. quantum cascade lasers) and detector development (e.g. multispectral sensors), as well as metrology issues and optical data transmission, are omitted since they belong to fundamental research journals. Using a more-or-less arbitrary order according to wavelength range, the issue starts with a paper on the physics of near-infrared photography using consumer product cameras in the spectral range from 800 nm to 1.1 µm [1]. It is followed by a series of three papers dealing with IR imaging in spectral ranges from 3 to 14 µm [2-4]. One of them deals with laboratory courses that may help to characterize the IR camera response [2], the second discusses potential applications for nondestructive testing techniques [3] and the third gives an example of how IR thermal imaging may be used to understand cloud cover of the Earth [4], which is the prerequisite for successful climate modelling. The next two papers cover the vast field of IR spectroscopy [5, 6]. The first of these deals with Fourier transform infrared spectroscopy in the spectral range from 2.5 to 25 µm, studying e.g. ro-vibrational excitations in gases or optical phonon interactions within solids [5]. The second deals mostly with the spectroscopy of liquids such as biofuels and special techniques such as attenuated total reflectance [6]. The two final papers deal with what se

Vollmer, M.

2013-11-01

141

Quantitative determination of maximal imaging depth in all-NIR multiphoton microscopy images of thick tissues  

NASA Astrophysics Data System (ADS)

We report two methods for quantitatively determining maximal imaging depth from thick tissue images captured using all-near-infrared (NIR) multiphoton microscopy (MPM). All-NIR MPM is performed using 1550 nm laser excitation with NIR detection. This method enables imaging more than five-fold deep in thick tissues in comparison with other NIR excitation microscopy methods. In this study, we show a correlation between the multiphoton signal along the depth of tissue samples and the shape of the corresponding empirical probability density function (pdf) of the photon counts. Histograms from this analysis become increasingly symmetric with the imaging depth. This distribution transitions toward the background distribution at higher imaging depths. Inspired by these observations, we propose two independent methods based on which one can automatically determine maximal imaging depth in the all-NIR MPM images of thick tissues. At this point, the signal strength is expected to be weak and similar to the background. The first method suggests the maximal imaging depth corresponds to the deepest image plane where the ratio between the mean and median of the empirical photon-count pdf is outside the vicinity of 1. The second method suggests the maximal imaging depth corresponds to the deepest image plane where the squared distance between the empirical photon-count mean obtained from the object and the mean obtained from the background is greater than a threshold. We demonstrate the application of these methods in all-NIR MPM images of mouse kidney tissues to study maximal depth penetration in such tissues.

Sarder, Pinaki; Akers, Walter J.; Sudlow, Gail P.; Yazdanfar, Siavash; Achilefu, Samuel

2014-02-01

142

Excite  

NSDL National Science Digital Library

Hot on the heels of AltaVista's Raging Search (see the May 5, 2000 Scout Report) comes another returned and (somewhat) slimmed-down search engine that focuses on relevant results. Like Raging Search, Excite's new Precision Search uses Google-style link analysis technology ("Deep Analysis") to help identify the most useful sites. Test queries produced consistently relevant results among the top few returns, though an indication of the number of total returns would be helpful, with two banner ads and (in some but not all cases) a Quick Results box on the left that could be quite handy for consumer-related searching. For instance, a search for "Plymouth" yielded links to research and comparisons, blue book values, financing, and service and repair information in the Quick Results box. I was also pleased to see that clicking on one of the other search categories (category, news, photo, audio/video) instantly produces returns for the original query, though the photo databases available seem somewhat limited compared to, say, AltaVista. While users searching for "official" sites will still do best at Google, those who also search for additional resources such as news, photos, and audio/video content may wish to give Excite Precision a run-through.

143

Origin of the low frequency radiation emitted by radiative polaritons excited by infrared radiation in planar La2O3 films  

NASA Astrophysics Data System (ADS)

Upon excitation in thin oxide films by infrared radiation, radiative polaritons are formed with complex angular frequency ?, according to the theory of Kliewer and Fuchs (1966 Phys. Rev. 150 573). We show that radiative polaritons leak radiation with frequency ?i to the space surrounding the oxide film. The frequency ?i is the imaginary part of ?. The effects of the presence of the radiation leaked out at frequency ?i are observed experimentally and numerically in the infrared spectra of La2O3 films on silicon upon excitation by infrared radiation of the 0TH type radiative polariton. The frequency ?i is found in the microwave to far infrared region, and depends on the oxide film chemistry and thickness. The presented results might aid in the interpretation of fine structures in infrared and, possibly, optical spectra, and suggest the study of other similar potential sources of electromagnetic radiation in different physical scenarios.

Vincent-Johnson, Anita J.; Schwab, Yosyp; Mann, Harkirat S.; Francoeur, Mathieu; Hammonds, James S., Jr.; Scarel, Giovanna

2013-01-01

144

Laser action in chromium-activated forsterite for near infrared excitation  

NASA Technical Reports Server (NTRS)

This paper reports on laser action in chromium-doped forsterite (Cr:Mg2SiO4) for 1064-nm excitation of the crystal's double-hump absorption band spanning the 850-1200-nm wavelength range. The cavity arrangement used for obtaining laser action in Cr:Mg2SiO2 was similar to that described by Petricevic et al. (1988). The fundamental and second harmonic emissions from a Q-switched Nd:YAG laser operating at a 10-Hz repetition rate were used for excitation of the NIR and visible bands, respectively. Pulsed laser action was readily observed for both the 1064-nm and 532-nm pumping at or above the respective thresholds. The laser parameters of the 532-nm and 1064-nm excitations were similar, indicating that the IR band is responsible for laser action for both excitations.

Petricevic, V.; Gayen, S. K.; Alfano, R. R.

1988-01-01

145

Infrared multiphoton dissociation of two perfluorobutenes  

E-print Network

. Activation a!Present address: NOAA, Aeronomy Laboratory, 325 Broadway, Boulder, CO 80303. b!Present address: Academia Sinica, Nankang, Taipei, 11529, Taiwan. 7202 J. Chem. Phys. 107 (18), 8 November 1997 0021-9606/97/107(18)/7202/7/$10.00 © 1997 American...

Longfellow, Cheryl A.; Berrie, Cindy L.; Suits, Arthur G.; Lee, Yuan T.

1997-08-04

146

Photosensitizer-doped conjugated polymer nanoparticles with high cross-sections for one- and two-photon excitation  

NASA Astrophysics Data System (ADS)

We report a novel nanoparticle that is promising for photodynamic therapy applications, which consists of a ?-conjugated polymer doped with a singlet oxygen photosensitizer. The nanoparticles exhibit highly efficient collection of excitation light due to the large excitation cross-section of the polymer. A quantum efficiency of singlet oxygen production of 0.5 was determined. Extraordinarily large two-photon excitation cross-sections were determined, indicating promise for near infrared multiphoton photodynamic therapy. Gel electrophoresis of DNA after near-UV irradiation in the presence of nanoparticles indicated both purine base and backbone DNA damage.We report a novel nanoparticle that is promising for photodynamic therapy applications, which consists of a ?-conjugated polymer doped with a singlet oxygen photosensitizer. The nanoparticles exhibit highly efficient collection of excitation light due to the large excitation cross-section of the polymer. A quantum efficiency of singlet oxygen production of 0.5 was determined. Extraordinarily large two-photon excitation cross-sections were determined, indicating promise for near infrared multiphoton photodynamic therapy. Gel electrophoresis of DNA after near-UV irradiation in the presence of nanoparticles indicated both purine base and backbone DNA damage. Electronic supplementary information (ESI) available: Fluorescence lifetime determination, AFM particle height histogram, and gel electrophoresis details. See DOI: 10.1039/c0nr00834f

Grimland, Jennifer L.; Wu, Changfeng; Ramoutar, Ria R.; Brumaghim, Julia L.; McNeill, Jason

2011-04-01

147

High-resolution infrared spectra of vibrationally excited HC4H in a supersonic hydrocarbon plasma jet  

NASA Astrophysics Data System (ADS)

High-resolution infrared spectra of diacetylene (HC4H) are recorded in the 3 ?m CH stretch region using continuous wave cavity ring-down spectroscopy (cw-CRDS). The HC4H molecules are generated in a pulsed and supersonic planar plasma expansion by discharging a C2H2/He/Ar gas mixture. The jet-cooling realizes a low rotational temperature of Trot ˜ 17 K. Vibrational temperatures are found to be relatively high, allowing the detection of vibrationally excited HC4H in direct absorption with energies up to 1800 cm-1. In total, sixteen ro-vibrational bands are identified, where nine of them were not reported before. Detailed and systematic rotational analyses are presented, yielding spectroscopic parameters for a series of vibrational levels over energy regions of 0-1800 and 3300-5100 cm-1. Using the observed infrared band intensities, two vibrational excitation temperatures of HC4H in the plasma jet, ˜570(50) K for the ?6, ?7 and ?8 bending vibrations, and ˜125(10) K for the ?9 bending vibration, are deduced.

Zhao, Dongfeng; Doney, Kirstin D.; Linnartz, Harold

2014-02-01

148

Ultrafast, large-field multiphoton microscopy based on an acousto-optic deflector and a spatial light modulator  

PubMed Central

We present an ultrafast, large-field multiphoton excitation fluorescence microscope with high lateral and axial resolutions based on a two-dimensional (2-D) acousto-optical deflector (AOD) scanner and spatial light modulator (SLM). When a phase-only SLM is used to shape the near-infrared light from a mode-locked titanium:sapphire laser into a multifocus array including the 0-order beam, a 136 ?m × 136 ?m field of view is achieved with a 60× objective using a 2-D AOD scanner without any mechanical scan element. The two-photon fluorescence image of a neuronal network that was obtained using this system demonstrates that our microscopy permits observation of dynamic biological events in a large field with high-temporal and -spatial resolution. PMID:22743445

Shao, Yonghong; Qin, Wan; Liu, Honghai; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z.

2013-01-01

149

Multiphoton nanosurgery in cells and tissues  

NASA Astrophysics Data System (ADS)

Multiphoton Microscopy with a femtosecond pulsed Ti:sapphire laser in the near infrared (NIR) enables the user not only to image cells and tissues with a subcellular resolution but also to perform highly precise nanosurgery. Intratissue compartments, single cells and even cell organelles like mitochondria, membranes or chromosomes can be manipulated and optically knocked out. Working at transient TW/cm2 laser intensities, single cells of tumor-sphaeroids were eliminated efficiently inside the sphaeroid without damaging the neighbour cells. Also single organelles of cells inside tissues could be optically knocked out with the nanoscalpel without collateral damage. Tissue structures inside a human tooth have been ablated with sizes below 1 ?m. This method may become a useful instrument for nano-manipulating and surgery in several fields of science, including targeted transfection.

Riemann, Iris; Anhut, Tiemo; Stracke, Frank; Le Harzic, Ronan; Koenig, Karsten

2005-04-01

150

Infrared spectra and molecular structure of excited electronic metastable states of the nitroprusside anion, [Fe(CN) 5NO] 2-  

NASA Astrophysics Data System (ADS)

Na 2[Fe(CN) 5NO].2H 2O (SNP) and Ba[Fe(CN) 5NO].3H 2O (BNP) irradiated at low temperature with light in the green—blue region exhibit two new sets of infrared (IR) bands. These can be assigned to two, long-lived, electronically excited metastable states of the [Fe(CN) 5NO] 2- (NP) ion. Upon heating, these states depopulate following decay processes with different onset temperatures. We considerably extend here previous polarized IR data on irradiated SNP (100) plates to include the other basal planes. All IR-active CN, NO and FeN stretching modes and FENO bending modes of NP in both metastable states exhibit frequency down shifts This points to a softening of the corresponding bonds upon excitation. Relative frequency shift values observed for modes associated with the FeNO group are about one order of magnitude larger than the corresponding values for CN stretching modes. This supports the conclusion that the metastable states are reached through an electronic transition involving mainly the metal( nd)-NO bonding. We employ dichroic measurements in SNP to estimate the orientation in the lattice of the transition dipole moment vector corresponding to the NO mode of NP in both metastable states. Results show that the FeNO group is not appreciably bent upon excitation of NP to either of these states.

Güida, J. A.; Aymonino, P. J.; Piro, O. E.; Castellano, E. E.

1993-04-01

151

Quantitative multiphoton imaging  

NASA Astrophysics Data System (ADS)

Certified clinical multiphoton tomographs for label-free multidimensional high-resolution in vivo imaging have been introduced to the market several years ago. Novel tomographs include a flexible 360° scan head attached to a mechanooptical arm for autofluorescence and SHG imaging as well as a CARS module. Non-fluorescent lipids and water, mitochondrial fluorescent NAD(P)H, fluorescent elastin, keratin, and melanin as well as SHG-active collagen can be imaged in vivo with submicron resolution in human skin. Sensitive and rapid detectors allow single photon counting and the construction of 3D maps where the number of detected photons per voxel is depicted. Intratissue concentration profiles from endogenous as well exogenous substances can be generated when the number of detected photons can be correlated with the number of molecules with respect to binding and scattering behavior. Furthermore, the skin ageing index SAAID based on the ratio elastin/collagen as well as the epidermis depth based on the onset of SHG generation can be determined.

König, Karsten; Weinigel, Martin; Breunig, Hans Georg; Uchugonova, Aisada

2014-02-01

152

Infrared/ultraviolet quadruple resonance spectroscopy to investigate structures of electronically excited states  

SciTech Connect

Molecular beam investigations in combination with IR/UV spectroscopy offer the possibility to obtain structural information on isolated molecules and clusters. One of the demanding tasks is the discrimination of different isomers, e.g., by the use of isomer specific UV excitations. If this discrimination fails due to overlaying UV spectra of different isomers, IR/IR methods offer another possibility. Here, we present a new IR/UV/IR/UV quadruple resonance technique to distinguish between different isomers especially in the electronically excited state. Due to the IR spectra, structural changes and photochemical pathways in excited states can be assigned and identified. The method is applied to the dihydrated cluster of 3-hydroxyflavone which has been investigated as photochemically relevant system and proton wire model in the S{sub 1} state. By applying the new IR/UV/IR/UV technique, we are able to show experimentally that both in the electronic ground (S{sub 0}) and the electronically excited state (S{sub 1}) two isomers have to be assigned.

Weiler, M.; Bartl, K.; Gerhards, M. [TU Kaiserslautern and Research Center Optimas, Fachbereich Chemie, Erwin-Schroedinger-Strasse 52, 67663 Kaiserslautern (Germany)

2012-03-21

153

Surface deactivation of vibrationally excited N2 studied using infrared titration combined with quantum cascade laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The wall de-excitation probability \\gamma_{N_{2}} of vibrationally excited nitrogen molecules was determined using infrared (IR) titration with CO, CO2 and N2O. Gas mixtures of N2 with 0.05-0.5% of CO (CO2 or N2O) were excited by a pulsed dc discharge at p = 133 Pa in a cylindrical discharge tube. During the afterglow, the vibrational relaxation of titrating molecules was monitored in situ with quantum cascade laser absorption spectroscopy. The value of \\gamma _{N_{2}} was deduced from measured vibrational relaxation times using a model of vibrational kinetics in N2. It was found that adsorption of IR tracers on the surface may increase the value of \\gamma _{N_{2}} by a factor up to two, depending on the molecule and the surface material. It was demonstrated that N2O is the most inert and reliable tracer and it was used for the determination of \\gamma_{N_{2}} on silica, Pyrex, TiO2, Al2O3 and anodized aluminum. Pretreatment of the silica surface by low-pressure plasma was found to have a strong effect on the vibrational de-excitation. Values of \\gamma_{N_{2}} measured after O2, Ar and N2 plasma pretreatment of the same silica discharge tube were 5.7 × 10-4, 8.2 × 10-4 and 11 × 10-4, respectively. This study clearly demonstrates that the presence of adsorbed atoms and molecules on the surface may significantly alter the value of \\gamma_{N_{2}} .

Marinov, D.; Lopatik, D.; Guaitella, O.; Ionikh, Y.; Röpcke, J.; Rousseau, A.

2014-01-01

154

Far-infrared spectroscopy of spin excitations and Dzyaloshinskii-Moriya interactions in the Shastry-Sutherland compound Sr Cu2 (B O3 )2  

Microsoft Academic Search

We have studied spin excitation spectra in the Shastry-Sutherland model compound SrCu2(BO3)2 in magnetic fields using far-infrared Fourier spectroscopy. The transitions from the ground singlet state to the triplet state at 24cm-1 and to several bound triplet states are induced by the electric field component of the far-infrared light. To explain the light absorption in the spin system we invoke

T. Rõõm; D. Hüvonen; U. Nagel; J. Hwang; T. Timusk; H. Kageyama

2004-01-01

155

Advances in multiphoton microscopy technology  

PubMed Central

Multiphoton microscopy has enabled unprecedented dynamic exploration in living organisms. A significant challenge in biological research is the dynamic imaging of features deep within living organisms, which permits the real-time analysis of cellular structure and function. To make progress in our understanding of biological machinery, optical microscopes must be capable of rapid, targeted access deep within samples at high resolution. In this Review, we discuss the basic architecture of a multiphoton microscope capable of such analysis and summarize the state-of-the-art technologies for the quantitative imaging of biological phenomena. PMID:24307915

Hoover, Erich E.; Squier, Jeff A.

2013-01-01

156

Excitation of Rydberg states in rubidium with near infrared diode lasers  

NASA Astrophysics Data System (ADS)

A system of three external cavity diode lasers is used to excite Rydberg states in rubidium. The 5S?5P?5D transitions are driven using lasers with ? = 780 and 776 nm respectively. From the 5D state, atoms fluoresce down to the 6P state. The final transition to Rydberg levels is from the 6P state with laser light near ? = 1016 nm. The nS and nD Rydberg states are accessible directly and with the application of a modest electric field nP states can also be excited. As a test of this system, Stark spectra are collected for nD and nP states.

Fahey, Donald P.; Noel, Michael W.

2011-08-01

157

Multiphoton microscopy based cryo-imaging of inflated frozen human lung sections at -60°C in healthy and COPD lungs  

NASA Astrophysics Data System (ADS)

Lung is a complex gas exchanger with interfacial area (where the gas exchange takes place) is about the size of a tennis court. Respiratory function is linked to the biomechanical stability of the gas exchange or alveolar regions which directly depends on the spatial distributions of the extracellular matrix fibers such fibrillar collagens and elastin fibers. It is very important to visualize and quantify these fibers at their native and inflated conditions to have correct morphometric information on differences between control and diseased states. This can be only achieved in the ex vivo states by imaging directly frozen lung specimens inflated to total lung capacity. Multiphoton microscopy, which uses ultra-short infrared laser pulses as the excitation source, produces multiphoton excitation fluorescence (MPEF) signals from endogenously fluorescent proteins (e.g. elastin) and induces specific second harmonic generation (SHG) signals from non-centrosymmetric proteins such as fibrillar collagens in fresh human lung tissues [J. Struct. Biol. (2010)171,189-196]. Here we report for the first time 3D image data obtained directly from thick frozen inflated lung specimens (~0.7- 1.0 millimeter thick) visualized at -60°C without prior fixation or staining in healthy and diseased states. Lung specimens donated for transplantation and released for research when no appropriate recipient was identified served as controls, and diseased lung specimens donated for research by patients receiving lung transplantation for very severe COPD (n=4) were prepared as previously described [N. Engl. J. Med. (2011) 201, 1567]. Lung slices evenly spaced between apex and base were examined using multiphoton microscopy while maintained at -60°C using a temperature controlled cold stage with a temperature resolution of 0.1°C. Infrared femto-second laser pulses tuned to 880nm, dry microscopic objectives, and non-de-scanned detectors/spectrophotometer located in the reflection geometry were used for generating the 3D images/spectral information. We found that this novel imaging approach can provide spatially resolved 3D images with spectral specificities from frozen inflated lungs that are sensitive enough to identity the micro-structural details of fibrillar collagens and elastin fibers in alveolar walls in both healthy and diseased tissues.

Abraham, Thomas; Kayra, Damian; Zhang, Angela; Suzuki, Masaru; McDonough, John; Elliott, W. M.; Cooper, Joel D.; Hogg, James C.

2013-02-01

158

Optical and Near Infrared Study of the Cepheus E outflow, a very low excitation object  

E-print Network

We present images and spectra of the Cepheus E (Cep E) region at both optical and infrared wavelengths. Only the brightest region of the southern lobe of the Cep E outflow reveals optical emission, suggesting that the extinction close to the outflow source plays an important r\\^ole in the observed difference between the optical and IR morphologies. Cep E is a unique object since it provides a link between the spectroscopic properties of the optical Herbig-Haro (HH) objects and those of deeply embedded outflows.

S. Ayala; A. Noriega-Crespo; P. M. Garnavich; S. Curiel; A. C. Raga; K. H. Bohm; J. Raymond

2000-04-20

159

Luminescence quenching of conductive Si nanocrystals via "Linkage emission": Hopping-like propagation of infrared-excited Auger electrons  

NASA Astrophysics Data System (ADS)

Phosphorus (P) is an n-type dopant for conductive silicon nanocrystals (Si-nc's), the electrical activation of which may be monitored through a non-radiative Auger recombination process that quenches the Si-nc luminescence. We investigated this quenching mechanism through electrical measurements of Si-nc's. Infrared-excited Auger electron emission as the non-radiative process was directly probed and the dynamics of the process are determined from a frequency response analysis. To explain the dynamics, we propose a model in which Auger electrons with a low kinetic energy establish a local inter-nanocrystal conductance and the repetition of this local conductance results in a constant photocurrent ("linkage emission"). This emission becomes significant by electron filling in the Si-nc's owing to the electrical activation of P, which is consistent with observed luminescence quenching behavior. We found that the IR photo-excited emission is distinct from the thermally induced hopping conduction and show that confined, rather than trapped, charges are the source of the Auger electrons. Thus, the process consumes both confined charges and the recombination energy for Auger emission, which explains the luminescence quenching mechanism of Si-nc:P.

Ishii, Masashi; Crowe, Iain F.; Halsall, Matthew P.; Knights, Andrew P.; Gwilliam, Russell M.; Hamilton, Bruce

2014-08-01

160

Molecular dynamics simulation of the homogeneous nucleation of UF6 molecules: Configurations and infrared spectra of the excited hot clusters  

NASA Astrophysics Data System (ADS)

The temperature, potential energy, and configurations of the clusters produced in the homogeneous nucleation of UF6 molecules from the supercooled (supersaturated) vapor phase were determined by classical molecular dynamics (MD) simulations. We observed two phenomena which demonstrate that the nucleation process occurs in the state far from thermal equilibrium. First, the excited hot clusters, the temperature of which is much higher than that of the monomer, were produced and continued to exist during the nucleation process. Second, the relationship between the potential energy and temperature of the clusters depends on the monomer temperature, that is, the potential energy at a temperature decreases with the increase in monomer temperature. In the simulations, various types of cluster configurations were observed: prolate, oblate, spherelike, and confeitolike. The confeitolike cluster is composed of one core and a few horns, and it was found predominantly in the hotter clusters. The infrared spectra of the UF6 clusters were calculated using a dipole-dipole and dipole-induced dipole interaction model and compared with those measured in a supercooled state by Tanimura et al. [J. Chem. Phys. 107, 7096 (1997)]. As a result, we found that the spectra measured in the supercooled state can be attributed to the excited hot clusters, the configuration of which are confeitolike.

Tanimura, Shinobu; Yasuoka, Kenji; Ebisuzaki, Toshikazu

2000-02-01

161

Anti-Stokes fluorescence from endogenously formed protoporphyrin IX – Implications for clinical multiphoton diagnostics  

PubMed Central

Multiphoton imaging based on two-photon excitation is making its way into the clinics, particularly for skin cancer diagnostics. It has been suggested that endogenously formed protoporphyrin IX (PpIX) induced by aminolevulinic acid or methylaminolevulinate can be applied to improve tumor contrast, in connection to imaging of tissue autofluorescence. However, previous reports are limited to cell studies and data from tissue are scarce. No report shows conclusive evidence that endogenously formed PpIX increases tumor contrast when performing multiphoton imaging in the clinical situation. We here demonstrate by spectral analysis that two-photon excitation of endogenously formed PpIX does not provide additional contrast in superficial basal cell carcinomas. In fact, the PpIX signal is overshadowed by the autofluorescent background. The results show that PpIX should be excited at a wavelength giving rise to one-photon anti-Stokes fluorescence, to overcome the autofluorescent background. Thus, this study reports on a plausible method, which can be implemented for clinical investigations on endogenously formed PpIX using multiphoton microscopy. Three-dimensional multiphoton microscopy images obtained from a superficial basal cell carcinoma illustrating higher porphyrin contrast when anti-stokes excitation (710 nm) is used compared to two-photon excitation (810 nm). PMID:22997024

Kantere, Despina; Guldbrand, Stina; Paoli, John; Goksör, Mattias; Hanstorp, Dag; Wennberg, Ann-Marie; Smedh, Maria; Ericson, Marica B

2013-01-01

162

Angle-and polarization-dependent collective excitation of plasmonic nanoarrays for surface enhanced infrared spectroscopy.  

PubMed

Our recent work has showed that diffractively coupled nanoplasmonic arrays for Fourier transform infrared (FTIR) microspectroscopy can enhance the Amide I protein vibrational stretch by up to 10(5) times as compared to plain substrates. In this work we consider computationally the impact of a microscope objective illumination cone on array performance. We derive an approach for computing angular- and spatially-averaged reflectance for various numerical aperture (NA) objectives. We then use this approach to show that arrays that are perfectly optimized for normal incidence undergo significant response degradation even at modest NAs, whereas arrays that are slightly detuned from the perfect grating condition at normal incidence irradiation exhibit only a slight drop in performance when analyzed with a microscope objective. Our simulation results are in good agreement with microscope measurements of experimentally optimized periodic nanoplasmonic arrays. PMID:21716349

Liberman, Vladimir; Adato, Ronen; Mertiri, Alket; Yanik, Ahmet A; Chen, Kai; Jeys, Thomas H; Erramilli, Shyamsunder; Altug, Hatice

2011-06-01

163

Infrared two-photon-excited visible lasing from a DNA-surfactant-chromophore complex  

NASA Astrophysics Data System (ADS)

Infrared two-photon-pumped and cavity-enhanced frequency upconversion lasing has been achieved in a novel DNA-surfactant-chromophore complex (DSCC) gel system, which is a new step toward producing a biological laser. Once the focused intensity of the 150 fs and ˜775 nm pump laser beam is higher than a certain threshold level, highly directional stimulated emission at ˜582 nm wavelength can be observed from a 1 cm long DSCC complex gel cell. With cavity feedback provided by the two optical windows, the pump threshold can be further reduced, the highly directional output lasing can be greatly enhanced, and the output spectral linewidth can be reduced to less than 1/5 of the spontaneous fluorescence spectral bandwidth.

He, Guang S.; Zheng, Qingdong; Prasad, Paras N.; Grote, James G.; Hopkins, Frank K.

2006-02-01

164

Infrared two-photon-excited visible lasing from a DNA-surfactant-chromophore complex.  

PubMed

Infrared two-photon-pumped and cavity-enhanced frequency upconversion lasing has been achieved in a novel DNA-surfactant-chromophore complex (DSCC) gel system, which is a new step toward producing a biological laser. Once the focused intensity of the 150 fs and approximately 775 nm pump laser beam is higher than a certain threshold level, highly directional stimulated emission at approximately 582 nm wavelength can be observed from a 1 cm long DSCC complex gel cell. With cavity feedback provided by the two optical windows, the pump threshold can be further reduced, the highly directional output lasing can be greatly enhanced, and the output spectral linewidth can be reduced to less than 1/5 of the spontaneous fluorescence spectral bandwidth. PMID:16480208

He, Guang S; Zheng, Qingdong; Prasad, Paras N; Grote, James G; Hopkins, Frank K

2006-02-01

165

Development of infrared sensors using energy transfer/energy upconversion processes: Study of laser excited fluorescence in rare Earth ion doped crystals  

NASA Technical Reports Server (NTRS)

A summary is presented of the spectroscopic study of three systems: LaF3:Ho(3+), LaF3:Er(3+) and CaF2:Nd(3+). When the D levels of Ho(3+) in LaF3 were resonantly excited with a laser beam of 640 nm, upconverted emissions were detected from J (416 nm), F (485 nm), and E (546 nm) levels. Energy upconverted emissions were also observed from F and E levels of Ho(3+) when the material was excited with an 800 nm near infrared laser. When the D levels of Er(3+) in LaF3 were resonantly excited with a laser beam of 637 nm, upconverted emissions were detected from the E (540 nm) and P (320, 400, and 468 nm) levels. Energy upconverted emissions were also observed from F, E, and D levels of Er(3+) when the material was resonantly excited with an 804 nm near infrared laser. When the D levels of Nd(3+) in CaF2 were resonantly excited with a laser beam of 577 nm, upconverted emissions were detected from the L (360 and 382 nm), K (418 nm), and I (432 nm) levels. Very weak upconverted emissions were detected when this system was irradiated with a near infrared laser. The numbers in parentheses are the wavelengths of the emissions.

Nash-Stevenson, S. K.; Reddy, B. R.; Venkateswarlu, P.

1994-01-01

166

Spread of cochlear excitation during stimulation with pulsed infrared radiation: Inferior colliculus measurements  

PubMed Central

Infrared neural stimulation (INS) has received considerable attention over the last few years. It provides an alternative method to artificially stimulate neurons without electrical current or the introduction of exogenous chromophores. One of the primary benefits of INS could be the improved spatial selectivity when compared with electrical stimulation. In the present study, we have evaluated the spatial selectivity of INS in the acutely damaged cochlea of guinea pigs and compared it to stimulation with acoustic tone pips in normal hearing animals. The radiation was delivered via a 200 ?m-diameter optical fiber, which was inserted through a cochleostomy into the scala tympani of the basal cochlear turn. The stimulated section along the cochlear spiral ganglion was estimated from the neural responses recorded from the central nucleus of the inferior colliculus (ICC). ICC responses were recorded in response to cochlear INS using a multichannel penetrating electrode array. Spatial tuning curves were constructed from the responses. For INS, approximately 55% of the activation profiles showed a single maximum, ~22% had two maxima, and ~13% had multiple maxima. The remaining 10% of the profiles occurred at the limits of the electrode array and could not be classified. The majority of ICC spatial tuning curves indicated that the spread of activation evoked by optical stimuli is comparable to that produced by acoustic pips. PMID:21828906

Richter, C.-P.; Rajguru, S.M.; Matic, A.I.; Moreno, E.L.; Fishman, A.J.; Robinson, A.M.; Suh, E.; Walsh, J.T.

2012-01-01

167

Spread of cochlear excitation during stimulation with pulsed infrared radiation: inferior colliculus measurements  

NASA Astrophysics Data System (ADS)

Infrared neural stimulation (INS) has received considerable attention over the last few years. It provides an alternative method to artificially stimulate neurons without electrical current or the introduction of exogenous chromophores. One of the primary benefits of INS could be the improved spatial selectivity when compared with electrical stimulation. In the present study, we have evaluated the spatial selectivity of INS in the acutely damaged cochlea of guinea pigs and compared it to stimulation with acoustic tone pips in normal-hearing animals. The radiation was delivered via a 200 µm diameter optical fiber, which was inserted through a cochleostomy into the scala tympani of the basal cochlear turn. The stimulated section along the cochlear spiral ganglion was estimated from the neural responses recorded from the central nucleus of the inferior colliculus (ICC). ICC responses were recorded in response to cochlear INS using a multichannel penetrating electrode array. Spatial tuning curves (STCs) were constructed from the responses. For INS, approximately 55% of the activation profiles showed a single maximum, ~22% had two maxima and ~13% had multiple maxima. The remaining 10% of the profiles occurred at the limits of the electrode array and could not be classified. The majority of ICC STCs indicated that the spread of activation evoked by optical stimuli is comparable to that produced by acoustic tone pips.

Richter, C.-P.; Rajguru, S. M.; Matic, A. I.; Moreno, E. L.; Fishman, A. J.; Robinson, A. M.; Suh, E.; Walsh, J. T., Jr.

2011-10-01

168

Plasma membrane nanoporation as a possible mechanism behind infrared excitation of cells  

NASA Astrophysics Data System (ADS)

Objective. Short infrared (IR) laser pulses have been used to stimulate action potentials in neurons both in vivo and in vitro. However, the mechanism(s) underlying this phenomenon has remained elusive. In vitro studies have found that pulsed IR exposure generates a nearly instant change in capacitance in the plasma membrane, characterized by inward rectification, a common feature in pore-forming exposures, such as electrical pulses and acoustic shock waves. Based on this similarity, we hypothesize that the mechanism of IR stimulation is the formation of short-lived nanopores in the plasma membrane. These transient, small-diameter pores allow the influx of extracellular ions that lead to action potential generation, possibly through activation of secondary messenger pathways or depolarization of the cell membrane resulting in activation of voltage-gated ion channels. Approach. A variety of fluorescent markers are used to observe the cell response to IR stimulation to monitor for effects indicative of nanoporation in other modalities. Main results. We observe rapid, transient rises in intracellular Ca2+, influx of YO-PRO-1 and propidium iodide into the cell signifying membrane permeabilization, cellular blebbing and swelling, and activation of the intracellular phosphoinositides lipid signaling pathway. Significance. This conclusion better explains the experimental observations and limitations of IR-induced neurological stimulation and represents a distinct theoretical shift in the understanding of the mechanism of IR-induced stimulation.

Beier, Hope T.; Tolstykh, Gleb P.; Musick, Joshua D.; Thomas, Robert J.; Ibey, Bennett L.

2014-12-01

169

Plasma membrane nanoporation as a possible mechanism behind infrared excitation of cells.  

PubMed

Objective. Short infrared (IR) laser pulses have been used to stimulate action potentials in neurons both in vivo and in vitro. However, the mechanism(s) underlying this phenomenon has remained elusive. In vitro studies have found that pulsed IR exposure generates a nearly instant change in capacitance in the plasma membrane, characterized by inward rectification, a common feature in pore-forming exposures, such as electrical pulses and acoustic shock waves. Based on this similarity, we hypothesize that the mechanism of IR stimulation is the formation of short-lived nanopores in the plasma membrane. These transient, small-diameter pores allow the influx of extracellular ions that lead to action potential generation, possibly through activation of secondary messenger pathways or depolarization of the cell membrane resulting in activation of voltage-gated ion channels. Approach. A variety of fluorescent markers are used to observe the cell response to IR stimulation to monitor for effects indicative of nanoporation in other modalities. Main results. We observe rapid, transient rises in intracellular Ca(2+), influx of YO-PRO-1 and propidium iodide into the cell signifying membrane permeabilization, cellular blebbing and swelling, and activation of the intracellular phosphoinositides lipid signaling pathway. Significance. This conclusion better explains the experimental observations and limitations of IR-induced neurological stimulation and represents a distinct theoretical shift in the understanding of the mechanism of IR-induced stimulation. PMID:25340253

Beier, Hope T; Tolstykh, Gleb P; Musick, Joshua D; Thomas, Robert J; Ibey, Bennett L

2014-12-01

170

Multiphoton polarization imaging of the stratum corneum and the dermis in ex-vivo human skin  

Microsoft Academic Search

In this work, we demonstrate the application of multiphoton polarization imaging in resolving the structures in surface stratum corneum and dermal layers of ex-vivo human skin. By varying the excitation and emission polarizations, we characterized the structural features in both Laurdan labeled stratum corneum and dermal fibers. The results presented here have important consequences in bioimaging applications of the skin.

Yen Sun; Jiunn-Wen Su; Wen Lo; Sun-Jan Lin; Shiou-Hwa Jee; Chen-Yuan Dong

2003-01-01

171

Addressable multiregional and multifocal multiphoton microscopy based on a spatial light modulator  

PubMed Central

Abstract. Through a combination of a deflective phase-only diffractive spatial light modulator (SLM) and galvo scanners, an addressable multiregional and multifocal multiphoton microscope (AM-MMM) is developed. The SLM shapes an incoming mode-locked, near-infrared Ti:sapphire laser beam into multiple beamlet arrays with addressable shapes and sizes that match the regions of interest on the sample. Compared with conventional multifocal multiphoton microscope (MMM), AM-MMM achieves the effective use of the laser power with an increase of imaging rate and a decrease of photodamage without sacrifice of resolution. PMID:22502556

Shao, Yonghong; Qin, Wan; Liu, Honghai; Qu, Junle; Peng, Xiang; Niu, Hanben; Gao, Bruce Z.

2012-01-01

172

Stochastic scanning multiphoton multifocal microscopy.  

PubMed

Multiparticle tracking with scanning confocal and multiphoton fluorescence imaging is increasingly important for elucidating biological function, as in the transport of intracellular cargo-carrying vesicles. We demonstrate a simple rapid-sampling stochastic scanning multifocal multiphoton microscopy (SS-MMM) fluorescence imaging technique that enables multiparticle tracking without specialized hardware at rates 1,000 times greater than conventional single point raster scanning. Stochastic scanning of a diffractive optic generated 10x10 hexagonal array of foci with a white noise driven galvanometer yields a scan pattern that is random yet space-filling. SS-MMM creates a more uniformly sampled image with fewer spatio-temporal artifacts than obtained by conventional or multibeam raster scanning. SS-MMM is verified by simulation and experimentally demonstrated by tracking microsphere diffusion in solution. PMID:19516485

Jureller, Justin E; Kim, Hee Y; Scherer, Norbert F

2006-04-17

173

Multi-Photon Quantum Interferometry  

Microsoft Academic Search

Based on the investigation of multi-photon entanglement, as produced by stimulated parametric down-conversion, a technique is presented to create heralded ``noon'' states. The relevance for interferometry will be discussed. Furthermore we explored the use of photon-number resolving detectors in Mach-Zehnder type of interferometers. Our current detectors can distinguish 0, 1, 2, to7, photon impacts. Although the overall collection and detection

Dirk Bouwmeester

2007-01-01

174

Far-infrared spectroscopy of spin excitations and Dzyaloshinskii-Moriya interactions in the Shastry-Sutherland compound SrCu2(BO3)2  

Microsoft Academic Search

We have studied spin excitation spectra in the Shastry-Sutherland model\\u000acompound SrCu$_2$(BO$_3$)$_2$ in magnetic fields using far-infrared Fourier\\u000aspectroscopy. The transitions from the ground singlet state to the triplet\\u000astate at 24 cm$^{-1}$ and to several bound triplet states are induced by the\\u000aelectric field component of the far-infrared light. To explain the light\\u000aabsorption in the spin system we

T. Rõõm; D. Hüvonen; U. Nagel; J. Hwang; T. Timusk; H. Kageyama

2004-01-01

175

Experimental demonstration of mode-selective phonon excitation of 6H-SiC by a mid-infrared laser with anti-Stokes Raman scattering spectroscopy  

NASA Astrophysics Data System (ADS)

Mode-selective phonon excitation by a mid-infrared laser (MIR-FEL) is demonstrated via anti-Stokes Raman scattering measurements of 6H-silicon carbide (SiC). Irradiation of SiC with MIR-FEL and a Nd-YAG laser at 14 K produced a peak where the Raman shift corresponds to a photon energy of 119 meV (10.4 ?m). This phenomenon is induced by mode-selective phonon excitation through the irradiation of MIR-FEL, whose photon energy corresponds to the photon-absorption of a particular phonon mode.

Yoshida, Kyohei; Sonobe, Taro; Zen, Heishun; Hachiya, Kan; Okumura, Kensuke; Mishima, Kenta; Inukai, Motoharu; Negm, Hani; Torgasin, Konstantin; Omer, Mohamed; Kii, Toshiteru; Masuda, Kai; Ohgaki, Hideaki

2013-10-01

176

Experimental demonstration of mode-selective phonon excitation of 6H-SiC by a mid-infrared laser with anti-Stokes Raman scattering spectroscopy  

SciTech Connect

Mode-selective phonon excitation by a mid-infrared laser (MIR-FEL) is demonstrated via anti-Stokes Raman scattering measurements of 6H-silicon carbide (SiC). Irradiation of SiC with MIR-FEL and a Nd-YAG laser at 14 K produced a peak where the Raman shift corresponds to a photon energy of 119 meV (10.4 ?m). This phenomenon is induced by mode-selective phonon excitation through the irradiation of MIR-FEL, whose photon energy corresponds to the photon-absorption of a particular phonon mode.

Yoshida, Kyohei; Hachiya, Kan; Okumura, Kensuke; Mishima, Kenta; Inukai, Motoharu; Torgasin, Konstantin; Omer, Mohamed [Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)] [Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Sonobe, Taro [Kyoto University Research Administration Office, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)] [Kyoto University Research Administration Office, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Zen, Heishun; Negm, Hani; Kii, Toshiteru; Masuda, Kai; Ohgaki, Hideaki [Institute of Advanced Energy, Kyoto University, Gokasyo, Uji, Kyoto 611-0011 (Japan)] [Institute of Advanced Energy, Kyoto University, Gokasyo, Uji, Kyoto 611-0011 (Japan)

2013-10-28

177

Coherent laser control of the resonance-enhanced multiphoton ionization of HCl  

NASA Astrophysics Data System (ADS)

Coherent control of the ionization of HCl was achieved by simulataneous 3+1 and 1+1 multiphoton excitation in a molecular beam machine, using either three 336 nm photons or one 112 nm photon to resonantly excite the intermediate j 3?-(?=0+) state. The phase difference between the two laser beams was continuously varied by passing the radiation through a cell containing either Ar or H2 gas.

Park, Seung Min; Lu, Shao-Ping; Gordon, Robert J.

1991-06-01

178

Multiphoton ionization\\/dissociation of cyclopentanone at the lower Rydberg states  

Microsoft Academic Search

The 2-photon excitation of the 3p and 3d Rydberg states in jet-cooled cyclopentanone has been investigated by resonance enhanced multiphoton ionization (REMPI) in a time of flight mass spectrometer. The three 3px,y,z components are clearly resolved while the case for the 3di excitations is obscure due to the S1 one-photon resonance. The ns laser induced mass spectra are characteristic of

John G. Philis; Constantine Kosmidis; Paraskevas Tzallas

1998-01-01

179

Wavefront sensorless adaptive optics temporal focusing-based multiphoton microscopy  

PubMed Central

Temporal profile distortions reduce excitation efficiency and image quality in temporal focusing-based multiphoton microscopy. In order to compensate the distortions, a wavefront sensorless adaptive optics system (AOS) was integrated into the microscope. The feedback control signal of the AOS was acquired from local image intensity maximization via a hill-climbing algorithm. The control signal was then utilized to drive a deformable mirror in such a way as to eliminate the distortions. With the AOS correction, not only is the axial excitation symmetrically refocused, but the axial resolution with full two-photon excited fluorescence (TPEF) intensity is also maintained. Hence, the contrast of the TPEF image of a R6G-doped PMMA thin film is enhanced along with a 3.7-fold increase in intensity. Furthermore, the TPEF image quality of 1?m fluorescent beads sealed in agarose gel at different depths is improved. PMID:24940539

Chang, Chia-Yuan; Cheng, Li-Chung; Su, Hung-Wei; Hu, Yvonne Yuling; Cho, Keng-Chi; Yen, Wei-Chung; Xu, Chris; Dong, Chen Yuan; Chen, Shean-Jen

2014-01-01

180

Application of Multiphoton Microscopy in Dermatological Studies: a Mini-Review  

PubMed Central

This review summarizes the historical and more recent developments of multiphoton microscopy, as applied to dermatology. Multiphoton microscopy offers several advantages over competing microscopy techniques: there is an inherent axial sectioning, penetration depths that compete well with confocal microscopy on account of the use of near-infrared light, and many two-photon contrast mechanisms, such as second-harmonic generation, have no analogue in one-photon microscopy. While the penetration depths of photons into tissue are typically limited on the order of hundreds of microns, this is of less concern in dermatology, as the skin is thin and readily accessible. As a result, multiphoton microscopy in dermatology has generated a great deal of interest, much of which is summarized here. The review covers the interaction of light and tissue, as well as the various considerations that must be made when designing an instrument. The state of multiphoton microscopy in imaging skin cancer and various other diseases is also discussed, along with the investigation of aging and regeneration phenomena, and finally, the use of multiphoton microscopy to analyze the transdermal transport of drugs, cosmetics and other agents is summarized. The review concludes with a look at potential future research directions, especially those that are necessary to push these techniques into widespread clinical acceptance. PMID:25075226

Yew, Elijah; Rowlands, Christopher

2014-01-01

181

Multiphoton quantum optics and quantum state engineering  

Microsoft Academic Search

We present a review of theoretical and experimental aspects of multiphoton quantum optics. Multiphoton processes occur and are important for many aspects of matter–radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric processes, and interferometry. A single review cannot account for all

Fabio Dell’Anno; Silvio De Siena; Fabrizio Illuminati

2006-01-01

182

Multiphoton Quantum Optics and Quantum State Engineering  

Microsoft Academic Search

We present a review of theoretical and experimental aspects of multiphoton quan- tum optics. Multiphoton processes occur and are important for many aspects of matter-radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric pro- cesses, and interferometry. A single review cannot account

Fabio Dell' Anno; Silvio De Siena; Fabrizio Illuminati

183

Multiphoton Path Entanglement by Nonlocal Bunching  

Microsoft Academic Search

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2005-01-01

184

Ex-vivo multiphoton analysis of rabbit corneal wound healing following photorefractive keratectomy  

NASA Astrophysics Data System (ADS)

The aim of this study is to assess the application of multiphoton autofluorescence and second harmonic generation (SHG) microscopy for investigating corneal wound healing after high myopic (-10.0D) photorefractive keratectomy (PRK) procedures on the rabbit eyes. The effect of PRK on the morphology and distribution of keratocytes were investigated using multiphoton excited autofluorescence imaging, while the effect of PRK on the arrangement of collagen fibers was monitored by second-harmonic generation imaging. Without histological processing, multiphoton microscopy is able to characterize corneal damage and wound healing from PRK. Our results show that this technique has potential application in the clinical evaluation of corneal damage due to refractive surgery, and may be used to study the unwanted side effects of these procedures.

Wang, Tsung-Jen; Lo, Wen; Dong, Chen-Yuan; Hu, Fung-Rong

2008-02-01

185

Distinguishing human normal or cancerous esophagus tissue ex vivo using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Application of multiphoton microscopy (MPM) to clinical cancer research has greatly developed over the last few years. In this paper, we mainly focus on two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG) for investigating esophageal cancer. We chiefly discuss the SHG/TPEF image and spectral characteristics of normal and cancerous esophagus submucosa with the combined multi-channel imaging mode and Lambda mode of a multiphoton microscope (LSM 510 META). Great differences can be detected, such as collagen content and morphology, glandular-shaped cancer cells, TPEF/SHG intensity ratio, and so on, which demonstrate that the multiphoton imaging technique has the potential ability for minimally-invasive early cancer diagnosis.

Liu, N. R.; Chen, G. N.; Wu, S. S.; Chen, R.

2014-02-01

186

Three-dimensional tooth imaging using multiphoton and second harmonic generation microscopy  

NASA Astrophysics Data System (ADS)

Detailed morphological and cellular information relating to the human tooth have traditionally been obtained through histological studies that required decalcification, staining, and fixation. With the recent invention of multiphoton microscopy, it has become possible to acquire high resolution images without histological procedures. Using an epiilluminated multiphoton microscope, we obtained two-photon excited autofluorescence and second harmonic generation (SHG) images of ex vivo human tooth. By combining these two imaging modalities we obtained submicron resolution images of the enamel, dentin, and the periodontal ligaments. The enamel emits endogenous two-photon autofluorescence. The structure of the dentin is visible from both the autofluorescence and second harmonic generation signals. The periodontal ligament composed mostly of collagen can be visualized by SHG imaging. We also constructed three dimensional images of the enamel, dentin, and periodontal ligament. The effectiveness of using multiphoton and second harmonic generation microscopy to obtain structural information of teeth suggest its potential use in dental diagnostics.

Chen, Min-Huey; Chen, Wei-Liang; Sun, Yen; Fwu, Peter Tramyeon; Lin, Ming-Gu; Dong, Chen-Yuan

2007-02-01

187

Low-energy excitations and dynamic Dzyaloshinskii-Moriya interaction in alpha'NaV2O5 studied by far-infrared spectroscopy  

Microsoft Academic Search

We have studied far-infrared transmission spectra of alpha'-NaV2O5 between 3 and 200 cm-1 in polarizations of incident light parallel to a, b, and c crystallographic axes in magnetic fields up to 33 T. The temperature dependence of the transmission spectra was studied close to and below the phase-transition temperature Tc=34 K. The triplet origin of an excitation at 65.4 cm-1

T. Rõõm; D. Hüvonen; U. Nagel; Y.-J. Wang; R. K. Kremer

2004-01-01

188

The multiphoton ionization of uranium hexafluoride  

SciTech Connect

Multiphoton ionization (MPI) time-of-flight mass spectroscopy and photoelectron spectroscopy studies of UF{sub 6} have been conducted using focused light from the Nd:YAG laser fundamental ({lambda}=1064 nm) and its harmonics ({lambda}=532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UF{sub x}{sup +} fragment ions even at the lowest laser power densities at which signal could be detected. The laser power dependence of U{sup n+} ions signals indicates that saturation can occur for many of the steps required for their ionization. In general, the doubly-charged uranium ion (U{sup 2+}) intensity is much greater than that of the singly-charged uranium ion (U{sup +}). For the case of the tunable dye laser experiments, the U{sup n+} (n = 1- 4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The dominance of the U{sup 2+} ion and the absence or very small intensities of UF{sub x}{sup +} fragments, along with the unsaturated wavelength dependence, indicate that mechanisms may exist other than ionization of bare U atoms after the stepwise photodissociation of F atoms from the parent molecule.

Armstrong, D.P. (Oak Ridge K-25 Site, TN (United States). UEO Enrichment Technical Operations Div.) [Oak Ridge K-25 Site, TN (United States). UEO Enrichment Technical Operations Div.

1992-05-01

189

Picosecond time-resolved infrared spectroscopic investigation into electron localisation in the excited states of Re(i) polypyridyl complexes with bridging ligands.  

PubMed

Mono- and binuclear complexes of (Re(CO)3Cl) with dipyrido[2,3-a:3',2'-c]-6,7-dimethylphenazine (ppbMe2) were synthesised and their photophysical properties probed using picosecond time-resolved infrared spectroscopy (TRIR). Excitation of these complexes in solution at 400 nm produces short-lived excited states. The IR spectrum of the excited state of the mononuclear [Re(CO)3Cl(ppbMe2)] have nu(CO) bands shifted to higher wavenumber relative to those of the ground state. This is consistent with formation of a (3)MLCT excited state. The IR spectrum of the excited state of the bimetallic [(Re(CO)3Cl)2(micro-ppbMe2)] shows the formation of two distinct groups of nu(CO) bands. This is interpreted as the formation of two distinct Re sites arising from a localised MLCT state with formally oxidised Re centre and a formally reduced bridging ligand. The nu(CO) bands of the adjacent Re centre are affected by the reduction of the bridging ligand. On the IR timescale the excited state structure is best formulated as [Cl(CO)3Re(II)(micro-ppbMe2 *-)Re(I)(CO)3Cl]. PMID:16395431

Kuimova, Marina K; Gordon, Keith C; Howell, Sarah L; Matousek, Pavel; Parker, Anthony W; Sun, Xue-Zhong; Towrie, Michael; George, Michael W

2006-01-01

190

Origin of near to middle infrared luminescence and energy transfer process of Er(3+)/Yb(3+)co-doped fluorotellurite glasses under different excitations.  

PubMed

We report the near to middle infrared luminescence and energy transfer process of Er(3+)/Yb(3+) co-doped fluorotellurite glasses under 980, 1550 and 800?nm excitations, respectively. Using a 980?nm laser diode pump, enhanced 1.5 and 2.7??m emissions from Er(3+):I13/2?(4)I15/2 and I11/2?(4)I13/2 transitions are observed, in which Yb(3+) ions can increase pumping efficiency and be used as energy transfer donors. Meanwhile, Yb(3+) can also be used as an acceptor and intensive upconversion luminescence of around 1000?nm is achieved from Er(3+):I11/2?(4)I15/2 and Yb(3+): F5/2?(4)F7/2 transitions using 1550?nm excitation. In addition, the luminescence properties and variation trendency by 800?nm excitation is similar to that using 1550?nm excitation. The optimum Er(3+) and Yb(3+) ion ratio is 1:1.5 and excess Yb(3+) ions decrease energy transfer efficiency under the two pumpings. These results indicate that Er(3+)/Yb(3+) co-doped fluorotellurite glasses are potential middle- infrared laser materials and may be used to increase the efficiency of the silicon solar cells. PMID:25648651

Huang, Feifei; Liu, Xueqiang; Ma, Yaoyao; Kang, Shuai; Hu, Lili; Chen, Danping

2015-01-01

191

Multispectral multiphoton lifetime analysis of human bladder tissue  

NASA Astrophysics Data System (ADS)

Human tissues intrinsically contain many fluorophores, as such NADH, elastin, collagen, and flavins, that can be excited and imaged using multiphoton microscopy, up to 150 ?m depth. In this work we have used combined two-photon excited fluorescence (TPE), fluorescence lifetime imaging microscopy (FLIM), and multispectral two photon emission detection (MTPE) to investigate different kinds of human ex-vivo fresh biopsies of bladder. Morphological and spectroscopic analyses have allowed to characterize both healthy and pathological tissue samples. In particular, we have examined tissue samples from healthy bladder mucosa, and bladder carcinoma in-situ (CIS), finding both morphological and spectroscopic differences. From the morphological point of view, cancer cells appeared more elongated with respect to corresponding normal cells; they also exhibited a different nucleus to cytoplasm ratio. From the spectroscopic point of view, we have found differences between the two tissue types in both spectral emission and fluorescence lifetime distribution. Even if further analysis, as well as a more significant statistics on a large number of samples would be helpful to discriminate between low and high grade cancer, our method is a promising tool to be used as diagnostic confirmation of histological results, as well as a diagnostic tool in a multiphoton endoscope or cystoscope to be used in in-vivo imaging applications.

Cicchi, Riccardo; Crisci, Alfonso; Nesi, Gabriella; Cosci, Alessandro; Giancane, Saverio; Carini, Marco; Pavone, Francesco S.

2009-02-01

192

Superresolution of Pulsed Multiphoton Raman Transitions  

SciTech Connect

We have investigated higher order multiphoton Raman resonances with two pulsed optical frequencies. Multiphoton transfer with up to 50photons is observed with milliwatts of laser power. We demonstrate that the spectral width of the multiphoton resonances can be far below the Fourier transform linewidth of the driving optical pulses. The functional dependence of the transition linewidth on the number of exchanged photons is found to vary with the pulse shape. Our experiment is performed with laser-cooled rubidium atoms confined in a CO{sub 2} -laser optical dipole trap.

Cataliotti, F. S.; Scheunemann, R.; Haensch, T. W.; Weitz, M.

2001-09-10

193

Excitation of the E2 and W1 "Arched" Filaments Near the Galactic Center as Deduced from Far-Infrared Spectroscopy  

NASA Technical Reports Server (NTRS)

We present measurements of the far-infrared (FIR) fine structure lines [S III] (33 microns), [Si II] (35 microns), [O III] (51, 88 microns), [O I] (63 microns) and [C II] (158 microns) and the adjacent continua along a scan crossing the E2 and W1 thermal radio filaments in the Galactic center 'Arc'. The deduced electron density and excitation vary along the scan by less than factors of two and three, respectively. The properties of the two filaments are similar: the line and continuum fluxes peak at the radio ridge, and the ridge/off-ridge contrast is greatest for the FIR continuum and ionized lines, lower for the single dish radio measurements (Sofue et al. 1986), and smallest for the low excitation lines. The spatial coincidence of the FIR and radio peaks demonstrates that any excitation mechanism for the radio continuum filaments must also account for the FIR line and continuum emission. The FIR luminosity of approx. 3 x 10(exp 5) Solar Luminosity per beam, and the association of [O III] emission with the filaments poses difficulties for shock and MHD models. Photoionization of molecular cloud edges by a random distribution of stars is the most likely excitation mechanism among those proposed. The continuum and the low excitation line fluxes are consistent with an origin in photodissociated molecular material adjacent to the photoionized gas.

Colgan, Sean W.J.; Erickson, Edwin F.; Simpson, Janet P.; Haas, Michael R.; Morris, Mark

1994-01-01

194

Femtosecond laser nanoprocessing using near-infrared nanojoule pulses at MHz repetition frequency  

NASA Astrophysics Data System (ADS)

Sub-80nm, sub-wavelength multiphoton nanoprocessing of silicon wafers as well as 3D maskless lithography by two two-photon polymerization in combination with five-dimensional (x,y,z, ?, ?) multiphoton analysis have been performed with the compact near infrared MHz femtosecond laser galvoscanning microscope FemtoCut (JenLab GmbH) as well as a modified ZEISS LSM510-NLO system. Laser excitation radiation was provided by a tuneable turnkey, one-box Chameleon as well as a MaiTai Ti:sapphire laser oscillator. Nanostructuring of silicon wafers with oil immersion objectives was based on NIR laser-induced periodic surface structures (LIPPS) likely due to selforganization processes. For the first time, periodic 70nm nanogrooves have been generated in wafers which is one order below the 800 nm laser wavelength by multiphoton phenomena at TW/cm2 transient intensities and low sub-3nJ pulse energies. Three-dimensional two-photon polymerization in SU-8 photoresists at GW/cm2 allowed rapid prototyping with sub-200nm precision. The same intensities have been used to image endogenous and exogenous fluorophores in a variety of materials for target finding and the evaluation of the nanoprocessing procedures.

König, Karsten; Schuck, Herbert; Sauer, Daniel; Bauerfeld, Frank; Stracke, Frank; Velten, Thomas; Tchernook, Andrei; Martin, Sven; Le Harzic, Ronan

2006-09-01

195

The effect of mid-infrared and far-infrared emission, generated at NH3 excitation by intense radiation of a TEA CO2 laser, on ammonia absorption  

Microsoft Academic Search

The effect of Mid-InfraRed (MIR) (lambda ? 12 mum) and Far-InfraRed (FIR) (lambda ≽ 100 mum) emission from excited ammonia on the absorption of intense radiation of a TEA CO2 laser has been studied experimentally under collisional and collisionless excitation conditions with ammonia pressures from 0.5 to 0.03 Torr. The energy of MIR and FIR emission was studied as a

R. S. Karve; V. N. Lokhman; G. N. Makarov

1996-01-01

196

Promising new wavelengths for multi-photon microscopy: thinking outside the Ti:Sapphire box  

NASA Astrophysics Data System (ADS)

Multi-photon excitation (MPE) imaging is dominated by the Ti:Sapphire laser as the source for excitation. However, it is limited when considering 3PE of common fluorophores and efficient 2PE of UV dyes which require wavelengths beyond the range of the Ti:Sapphire. Two ultra-short pulsed sources are presented as alternatives: a novel optical parametric oscillator (OPO) geometry (1400-1600nm) and the sum-frequency mixing of an OPO and Yb-doped fibre laser, providing a tunable output (626-635nm). For long wavelengths, we report three-photon laser scanning microscopy (3PLSM) using a bi-directional pumped optical parametric oscillator (OPO) with signal wavelength output at 1500 nm. This novel laser was used to overcome the high optical loss in the infrared spectral region observed in laser scanning microscopes and objective lenses that renders them otherwise difficult to use for imaging. To test our system, we performed 3PLSM auto-fluorescence imaging of live plant cells at 1500 nm, specifically Spirogyra, and compared performance with two-photon excitation (2PLSM) imaging using a femtosecond pulsed Ti:Sapphire laser at 780 nm. Analysis of cell viability based on cytoplasmic organelle streaming and structural changes of cells revealed that at similar peak powers, 2PLSM caused gross cell damage after 5 minutes but 3PLSM showed little or no interference with cell function after 15 minutes. The 1500 nm OPO was thus shown to be a practical laser source for live cell imaging. For short wavelengths, we report the use of an all-solid-state ultra-short pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involved sumfrequency mixing of the output from the long-wavelength OPO described above with residual pump radiation to generate fs-pulsed output in the red spectral region. We demonstrated the performance of our ultra-short pulsed system using fluorescently labelled and autofluorescent tissue, and compared with conventional Ti:Sapphire excitation. We observed a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination powers of 22 mW or less.

Norris, Greg; Amor, Rumelo; Dempster, John; Amos, William B.; McConnell, Gail

2013-02-01

197

Multiphoton Quantum Optics and Quantum State Engineering  

E-print Network

We present a review of theoretical and experimental aspects of multiphoton quantum optics. Multiphoton processes occur and are important for many aspects of matter-radiation interactions that include the efficient ionization of atoms and molecules, and, more generally, atomic transition mechanisms; system-environment couplings and dissipative quantum dynamics; laser physics, optical parametric processes, and interferometry. A single review cannot account for all aspects of such an enormously vast subject. Here we choose to concentrate our attention on parametric processes in nonlinear media, with special emphasis on the engineering of nonclassical states of photons and atoms. We present a detailed analysis of the methods and techniques for the production of genuinely quantum multiphoton processes in nonlinear media, and the corresponding models of multiphoton effective interactions. We review existing proposals for the classification, engineering, and manipulation of nonclassical states, including Fock states...

Dell'Anno, F; Illuminati, F; 10.1016/j.physrep.2006.01.004

2009-01-01

198

Multiphoton Path Entanglement by Nonlocal Bunching  

NASA Astrophysics Data System (ADS)

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.

Eisenberg, H. S.; Hodelin, J. F.; Khoury, G.; Bouwmeester, D.

2005-03-01

199

Multiphoton Path Entanglement by Nonlocal Bunching  

Microsoft Academic Search

Multiphoton path entanglement is created without applying post-selection, by\\u000amanipulating the state of stimulated parametric down-conversion. A specific\\u000ameasurement on one of the two output spatial modes leads to the non-local\\u000abunching of the photons of the other mode, forming the desired multiphoton path\\u000aentangled state. We present experimental results for the case of a heralded\\u000atwo-photon path entangled state

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2005-01-01

200

Multiphoton path entanglement by nonlocal bunching.  

PubMed

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers. PMID:15783951

Eisenberg, H S; Hodelin, J F; Khoury, G; Bouwmeester, D

2005-03-11

201

How periodic orbit bifurcations drive multiphoton ionization  

E-print Network

The multiphoton ionization of hydrogen by a strong bichromatic microwave field is a complex process prototypical for atomic control research. Periodic orbit analysis captures this complexity: Through the stability of periodic orbits we can match qualitatively the variation of experimental ionization rates with a control parameter, the relative phase between the two modes of the field. Moreover, an empirical formula reproduces quantum simulations to a high degree of accuracy. This quantitative agreement shows how short periodic orbits organize the dynamics in multiphoton ionization.

S. Huang; C. Chandre; T. Uzer

2006-12-26

202

Multimodal microscopy and the stepwise multi-photon activation fluorescence of melanin  

NASA Astrophysics Data System (ADS)

The author's work is divided into three aspects: multimodal microscopy, stepwise multi-photon activation fluorescence (SMPAF) of melanin, and customized-profile lenses (CPL) for on-axis laser scanners, which will be introduced respectively. A multimodal microscope provides the ability to image samples with multiple modalities on the same stage, which incorporates the benefits of all modalities. The multimodal microscopes developed in this dissertation are the Keck 3D fusion multimodal microscope 2.0 (3DFM 2.0), upgraded from the old 3DFM with improved performance and flexibility, and the multimodal microscope for targeting small particles (the "Target" system). The control systems developed for both microscopes are low-cost and easy-to-build, with all components off-the-shelf. The control system have not only significantly decreased the complexity and size of the microscope, but also increased the pixel resolution and flexibility. The SMPAF of melanin, activated by a continuous-wave (CW) mode near-infrared (NIR) laser, has potential applications for a low-cost and reliable method of detecting melanin. The photophysics of melanin SMPAF has been studied by theoretical analysis of the excitation process and investigation of the spectra, activation threshold, and photon number absorption of melanin SMPAF. SMPAF images of melanin in mouse hair and skin, mouse melanoma, and human black and white hairs are compared with images taken by conventional multi-photon fluorescence microscopy (MPFM) and confocal reflectance microscopy (CRM). SMPAF images significantly increase specificity and demonstrate the potential to increase sensitivity for melanin detection compared to MPFM images and CRM images. Employing melanin SMPAF imaging to detect melanin inside human skin in vivo has been demonstrated, which proves the effectiveness of melanin detection using SMPAF for medical purposes. Selective melanin ablation with micrometer resolution has been presented using the Target system. Compared to the traditional selective photothermolysis, this method demonstrates higher precision, higher specificity and deeper penetration. Therefore, the SMPAF guided selective ablation of melanin is a promising tool of removing melanin for both medical and cosmetic purposes. Three CPLs have been designed for low-cost linear-motion scanners, low-cost fast spinning scanners and high-precision fast spinning scanners. Each design has been tailored to the industrial manufacturing ability and market demands.

Lai, Zhenhua

203

Fine tunable red-green upconversion luminescence from glass ceramic containing 5%Er3+:NaYF4 nanocrystals under excitation of two near infrared femtosecond lasers  

NASA Astrophysics Data System (ADS)

In this paper, we report fine tunable red-green upconversion luminescence of glass ceramic containing 5%Er3+: NaYF4 nanocrystals excited simultaneously by two near infrared femtosecond lasers. When the glass ceramic was irradiated by 800 nm femtosecond laser, weak red emission centered at 670 nm was detected. Bright red light was observed when the fs laser wavelength was tuned to 1490 nm. However, when excited by the two fs lasers simultaneously, the sample emitted bright green light centered at 550 nm, while the red light kept the same intensity. The dependences of the red and the green light intensities on the two pump lasers are much different, which enables us to manipulate the color emission by adjusting the two pump laser intensities, respectively. We present a theoretical model of Er3+ ions interacting with two fs laser fields, and explain well the experimental results.

Shang, Xiaoying; Chen, Ping; Cheng, Wenjing; Zhou, Kan; Ma, Jing; Feng, Donghai; Zhang, Shian; Sun, Zhenrong; Qiu, Jianrong; Jia, Tianqing

2014-08-01

204

Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2O2Cl  

NASA Astrophysics Data System (ADS)

Infrared reflection as a function of temperature has been measured on the anisotropic single-crystal Cu3Bi(SeO3)2O2Cl. The complex dielectric function and optical properties along all three crystal axes of the orthorhombic cell were obtained via Kramers-Kronig analysis and by fits to a Drude-Lorentz model. Below 110 K drastic anomalies in the phonon spectrum (e.g., new modes and splitting of existing modes) are observed along all three crystal axes. Transmission in the terahertz region as a function of temperature has revealed magnetic excitations originating below the ferromagnetic ordering temperature, Tc=24 K. The origin of the excitations in the magnetic state will be discussed in terms of their polarization and externally-applied magnetic field dependence.

Miller, Kevin H.; Martin, C.; Xi, X.; Berger, H.; Carr, G. L.; Tanner, D. B.

2012-02-01

205

Resonantly enhanced vacuum-ultraviolet generation and multiphoton ionization in carbon monoxide gas  

SciTech Connect

Competition between three-photon resonantly enhanced vacuum ultraviolet third-harmonic generation and six-photon multiphoton ionization using the A state in gaseous carbon monoxide is observed. Excitation spectra of the third-harmonic emission exhibit increasing blue shifts and broadening with increasing pressure due to the phase matching requirements. Estimates for the efficiency and tunability show that third-harmonic generation in carbon monoxide molecules is a promising source for coherent vacuum ultraviolet light.

Glownia, J.H.; Sander, R.K.

1982-01-01

206

Experimental measurements of multiphoton enhanced air breakdown by a subthreshold intensity excimer laser  

SciTech Connect

This work presents density, spectroscopic temperature, and shockwave measurements of laser induced breakdown plasma in atmospheric air by subthreshold intensity (5.5x10{sup 9} W/cm{sup 2}) 193 nm laser radiation. Using molecular spectroscopy and two-wavelength interferometry, it is shown that substantial ionization (>10{sup 16} cm{sup -3}) occurs that is not predicted by collisional cascade (CC) breakdown theory. While the focused laser irradiance is three orders of magnitude below the theoretical collisional breakdown threshold, the substantial photon energy at 193 nm (6.42 eV/photon) compared with the ionization potential of air (15.6 eV) significantly increases the probability of multiphoton ionization effects. By spectroscopically monitoring the intensity of the N{sub 2}{sup +} first negative system (B {sup 2}SIGMA{sub u}{sup +}-X {sup 2}SIGMA{sub g}{sup +}) vibrational bandhead (v{sup '}=0,v{sup ''}=0) at low pressure (20 Torr) where multiphoton effects are dominant, it is shown that two photon excitation, resonant enhanced multiphoton ionization is the primary mechanism for quantized ionization of N{sub 2} to the N{sub 2}{sup +}(B {sup 2}SIGMA{sub u}{sup +}) state. This multiphoton effect then serves to amplify the collisional breakdown process at higher pressures by electron seeding, thereby reducing the threshold intensity from that required via CC processes for breakdown and producing high density laser formed plasmas.

Way, Jesse; Hummelt, Jason; Scharer, John [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53706 (United States)

2009-10-15

207

ALMA DETECTION OF THE VIBRATIONALLY EXCITED HCN J = 4-3 EMISSION LINE IN THE AGN-HOSTING LUMINOUS INFRARED GALAXY IRAS 20551–4250  

SciTech Connect

We present results from our ALMA Cycle 0 observations, at the frequencies around the HCN, HCO{sup +}, and HNC J = 4-3 transition lines, of the luminous infrared galaxy IRAS 20551–4250 at z = 0.043, which is known to host an energetically important obscured active galactic nucleus (AGN). In addition to the targeted HCN, HCO{sup +}, and HNC J = 4-3 emission lines, two additional strong emission lines are seen, which we attribute to H{sub 2}S and CH{sub 3}CN(+CCH). The HCN-to-HCO{sup +} J = 4-3 flux ratio (?0.7) is higher than in the other starburst-dominated galaxy (?0.2) observed in our ALMA Cycle 0 program. We tentatively (?5?) detected the vibrationally excited (v {sub 2} = 1) HCN J = 4-3 (l = 1f) emission line, which is important for testing an infrared radiative pumping scenario for HCN. This is the second detection of this molecular transition in external galaxies. The most likely reason for this detection is not only the high flux of this emission line, but also the small molecular line widths observed in this galaxy, suggesting that vibrational excitation of HCN may be relatively common in AGN-hosting galaxies.

Imanishi, Masatoshi [Subaru Telescope, 650 North A'ohoku Place, Hilo, Hawaii, 96720 (United States); Nakanishi, Kouichiro, E-mail: masa.imanishi@nao.ac.jp [Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura 763-0355, Santiago de Chile (Chile)

2013-10-01

208

Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2O2Cl  

NASA Astrophysics Data System (ADS)

Infrared reflection and transmission as a function of temperature have been measured on single crystals of Cu3Bi(SeO3)2O2Cl. The complex dielectric function and optical properties along all three principal axes of the orthorhombic cell were obtained via Kramers-Kronig analysis and by fits to a Drude-Lorentz model. Below 115 K, 16 additional modes [8(E?â)+6(E?b?)+2(E??)] appear in the phonon spectra; however, powder x-ray diffraction measurements do not detect a new structure at 85 K. Potential explanations for the new phonon modes are discussed. Transmission in the far infrared as a function of temperature has revealed magnetic excitations originating below the magnetic ordering temperature (Tc˜24 K). The origin of the excitations in the magnetically ordered state will be discussed in terms of their response to different polarizations of incident light, behavior in externally applied magnetic fields, and the anisotropic magnetic properties of Cu3Bi(SeO3)2O2Cl as determined by dc susceptibility measurements.

Miller, K. H.; Stephens, P. W.; Martin, C.; Constable, E.; Lewis, R. A.; Berger, H.; Carr, G. L.; Tanner, D. B.

2012-11-01

209

Activatable Organic Near-Infrared Fluorescent Probes Based on a Bacteriochlorin Platform: Synthesis and Multicolor in Vivo Imaging with a Single Excitation  

PubMed Central

Near infrared (NIR) fluorescent probes are ideal for in vivo imaging because they offer deeper tissue penetration and lower background autofluorescence. Although most fluorophores in this range are cyanine-based dyes, several new classes of fluorescent NIR probes have been developed. In this study, we developed organic bacteriochlorin derivatives, NMP4 and NMP5, which are excited with a single green light and emit different narrow, well-resolved bands in the NIR (peak of 739 and 770 nm for NMP4 and NMP5, respectively). When conjugated to galactosyl-human serum albumin (hGSA) or glucosyl-human serum albumin (glu-HSA), both targeting H-type lectins, including the ?-d-galactose receptor expressing on ovarian cancer, these agents become targeted, activatable, single excitation, multicolor NIR fluorescence probes. After conjugation to either glu-HSA or hGSA, substantial quenching of fluorescence occurs that is reversed after cell binding and internalization. In vitro studies showed higher cancer cell uptake with NMP4 or NMP5 conjugated to hGSA compared to the same conjugates with glu-HSA. In vivo single excitation two-color imaging was performed after intraperitoneal injection of these agents into mice with disseminated ovarian cancer. Excited with a single green light, distinct NIR emission spectra from each fluorophore were detected and could be distinguished with spectral unmixing. In vivo results using a red fluorescence protein (RFP) labeled tumor model of disseminated ovarian cancer demonstrated high sensitivity and specificity for all probes. The success of single excitation, 2-color NIR fluorescence imaging with a new class of bacteriochlorin-based activatable fluorophores, NMP4 and NMP5, paves the way for further exploration of noncyanine dye-based NIR fluorophores. PMID:24450401

2015-01-01

210

Label-free multi-photon imaging using a compact femtosecond fiber laser mode-locked by carbon nanotube saturable absorber  

PubMed Central

We demonstrate label-free multi-photon imaging of biological samples using a compact Er3+-doped femtosecond fiber laser mode-locked by a single-walled carbon nanotube (CNT). These compact and low cost lasers have been developed by various groups but they have not been exploited for multiphoton microscopy. Here, it is shown that various multiphoton imaging modalities (e.g. second harmonic generation (SHG), third harmonic generation (THG), two-photon excitation fluorescence (TPEF), and three-photon excitation fluorescence (3PEF)) can be effectively performed on various biological samples using a compact handheld CNT mode-locked femtosecond fiber laser operating in the telecommunication window near 1560nm. We also show for the first time that chlorophyll fluorescence in plant leaves and diatoms can be observed using 1560nm laser excitation via three-photon absorption. PMID:24156074

Kieu, K.; Mehravar, S.; Gowda, R.; Norwood, R. A.; Peyghambarian, N.

2013-01-01

211

Label-free multi-photon imaging using a compact femtosecond fiber laser mode-locked by carbon nanotube saturable absorber.  

PubMed

We demonstrate label-free multi-photon imaging of biological samples using a compact Er(3+)-doped femtosecond fiber laser mode-locked by a single-walled carbon nanotube (CNT). These compact and low cost lasers have been developed by various groups but they have not been exploited for multiphoton microscopy. Here, it is shown that various multiphoton imaging modalities (e.g. second harmonic generation (SHG), third harmonic generation (THG), two-photon excitation fluorescence (TPEF), and three-photon excitation fluorescence (3PEF)) can be effectively performed on various biological samples using a compact handheld CNT mode-locked femtosecond fiber laser operating in the telecommunication window near 1560nm. We also show for the first time that chlorophyll fluorescence in plant leaves and diatoms can be observed using 1560nm laser excitation via three-photon absorption. PMID:24156074

Kieu, K; Mehravar, S; Gowda, R; Norwood, R A; Peyghambarian, N

2013-01-01

212

Measurements of multiphoton action cross sections for multiphoton microscopy  

PubMed Central

We report quantitative measurements of two-, three-, and four-photon excitation action cross sections of several commonly used fluorophores and fluorescent proteins at three different excitation wavelengths of 800 nm, 1300 nm, and 1680 nm. The measured cross section values are consistent with simple quantum mechanic estimations. These values indicate that the optimum repetition rate for deep tissue 3-photon microscopy is approximately 1 to 2 MHz. We further demonstrate that it is feasible to perform 4-photon fluorescence microscopy of GFP labeled microglia in mouse brain in vivo at 1700 nm. 4-photon excitation increases the accessibility of fluorophores at the long wavelength spectral window of 1700 nm. PMID:25360361

Cheng, Li-Chung; Horton, Nicholas G.; Wang, Ke; Chen, Shean-Jen; Xu, Chris

2014-01-01

213

Multi-Photon Quantum Interferometry  

NASA Astrophysics Data System (ADS)

Based on the investigation of multi-photon entanglement, as produced by stimulated parametric down-conversion, a technique is presented to create heralded ``noon'' states. The relevance for interferometry will be discussed. Furthermore we explored the use of photon-number resolving detectors in Mach-Zehnder type of interferometers. Our current detectors can distinguish 0, 1, 2, to7, photon impacts. Although the overall collection and detection efficiency of photons is well below unity (about 0.3) the photon number resolving property is still very useful if combined with coherent input states since those state are eigenstates of the photon annihilation operator. First we analyze the coherent state interferometer with a single photon-number resolving detector, revealing the strong non-linear response of an interferometer in the case of Fock-state projection. Second, we use two such detectors together with a Baysian phase estimation strategy to demonstrate that it is possible to achieve the standard quantum limit independently from the true value of the phase shift. This protocol is unbiased and saturates the Cramer-Rao phase uncertainty bound and, therefore, is an optimal phase estimation strategy. As a final topic it will be shown how quantum interferometry combined with micromechanical structures can be used to investigate quantum superpositions and quantum decoherence of macroscopic objects.

Bouwmeester, Dirk

2007-06-01

214

Near infrared excited micro-Raman spectra of 4:1 methanol-ethanol mixture and ruby fluorescence at high pressure  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) lasers, as a new excitation source for Raman spectroscopy, has shown its unique advantages and is being increasingly used for some special samples, such as those emitting strong fluorescence in the visible region. This article focuses on some issues related to high-pressure micro-Raman spectroscopy using NIR excitation source. The Raman spectra of 4:1 methanol-ethanol mixture (4:1 M-E) show a linear variation in both Raman shifts and linewidths under pressure up to 18 GPa. This result is useful in distinguishing Raman scattering of samples from that of the alcohol mixture, an extensively used pressure-transmitting medium. The R1 fluorescence in the red region induced by two-photon absorption of the NIR laser is strong enough to be used as pressure scale. The frequency and line width of the R1 lines are very sensitive to pressure change and the glass transition of the pressure medium. Our results manifest that it is reliable and convenient to use NIR induced two-photon excited fluorescence of ruby for both pressure calibration and distribution of pressure in the 4:1 M-E pressure transmitting medium.

Wang, X. B.; Shen, Z. X.; Tang, S. H.; Kuok, M. H.

1999-06-01

215

Long-wavelength infrared surface plasmons on Ga-doped ZnO films excited via 2D hole arrays for extraordinary optical transmission  

NASA Astrophysics Data System (ADS)

Extraordinary optical transmission (EOT) through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) and can be tuned utilizing the physical structure size such as period. Pulse laser deposited Ga-doped ZnO has been shown to have fluctuations in optical and electrical parameters based on fabrication techniques, providing a complimentary tuning means. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. Optical reflection measurements completed with a microscope coupled FTIR system contain absorption resonances that are in agreement with analytical theories for excitation of SPPs on 2D structures. EOT through Ga-doped ZnO is numerically demonstrated at wavelengths where SPPs are excited. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms.

Cleary, Justin W.; Esfahani, Nima Nader; Vangala, Shivashankar; Guo, Junpeng; Hendrickson, Joshua R.; Leedy, Kevin D.; Thomson, Darren; Look, David C.

2013-09-01

216

Optical and Near-Infrared Study of the Cepheus E Outflow, A Very Low-Excitation Object  

Microsoft Academic Search

We present images and spectra of the Cepheus E (Cep E) region at both optical and infrared wavelengths. Only the brightest region of the southern lobe of the Cep E outflow reveals optical emission, suggesting that the extinction close to the outflow source plays an important role in the observed difference between the optical and IR morphologies. Cep E is

S. Ayala; A. Noriega-Crespo; P. M. Garnavich; S. Curiel; A. C. Raga; K.-H. Böhm; J. Raymond

2000-01-01

217

Multiphoton microscopy in defining liver function  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is the preferred method when in vivo deep-tissue imaging is required. This review presents the application of multiphoton microscopy in defining liver function. In particular, multiphoton microscopy is useful in imaging intracellular events, such as mitochondrial depolarization and cellular metabolism in terms of NAD(P)H changes with fluorescence lifetime imaging microscopy. The morphology of hepatocytes can be visualized without exogenously administered fluorescent dyes by utilizing their autofluorescence and second harmonic generation signal of collagen, which is useful in diagnosing liver disease. More specific imaging, such as studying drug transport in normal and diseased livers are achievable, but require exogenously administered fluorescent dyes. If these techniques can be translated into clinical use to assess liver function, it would greatly improve early diagnosis of organ viability, fibrosis, and cancer.

Thorling, Camilla A.; Crawford, Darrell; Burczynski, Frank J.; Liu, Xin; Liau, Ian; Roberts, Michael S.

2014-09-01

218

Human bladder cancer diagnosis using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

At the time of diagnosis, approximately 75% of bladder cancers are non-muscle invasive. Appropriate diagnosis and surgical resection at this stage improves prognosis dramatically. However, these lesions, being small and/or flat, are often missed by conventional white-light cystoscopes. Furthermore, it is difficult to assess the surgical margin for negativity using conventional cystoscopes. Resultantly, the recurrence rates in patients with early bladder cancer are very high. This is currently addressed by repeat cystoscopies and biopsies, which can last throughout the life of a patient, increasing cost and patient morbidity. Multiphoton endoscopes offer a potential solution, allowing real time, noninvasive biopsies of the human bladder, as well as an up-close assessment of the resection margin. While miniaturization of the Multiphoton microscope into an endoscopic format is currently in progress, we present results here indicating that Multiphoton imaging (using a bench-top Multiphoton microscope) can indeed identify cancers in fresh, unfixed human bladder biopsies. Multiphoton images are acquired in two channels: (1) broadband autofluorescence from cells, and (2) second harmonic generation (SHG), mostly by tissue collagen. These images are then compared with gold standard hematoxylin/eosin (H&E) stained histopathology slides from the same specimen. Based on a "training set" and a very small "blinded set" of samples, we have found excellent correlation between the Multiphoton and histopathological diagnoses. A larger blinded analysis by two independent uropathologists is currently in progress. We expect that the conclusion of this phase will provide us with diagnostic accuracy estimates, as well as the degree of inter-observer heterogeneity.

Mukherjee, Sushmita; Wysock, James S.; Ng, Casey K.; Akhtar, Mohammed; Perner, Sven; Lee, Ming-Ming; Rubin, Mark A.; Maxfield, Frederick R.; Webb, Watt W.; Scherr, Douglas S.

2009-02-01

219

Multiphoton polymerization using optical trap assisted nanopatterning  

NASA Astrophysics Data System (ADS)

In this letter, we show the combination of multiphoton polymerization and optical trap assisted nanopatterning (OTAN) for the additive manufacturing of structures with nanometer resolution. User-defined patterns of polymer nanostructures are deposited on a glass substrate by a 3.5 ?m polystyrene sphere focusing IR femtosecond laser pulses, showing minimum feature sizes of ?/10. Feature size depends on the applied laser fluence and the bead surface spacing. A finite element model describes the intensity enhancement in the microbead focus. The results presented suggest that OTAN in combination with multiphoton processing is a viable technique for additive nanomanufacturing with sub-diffraction-limited resolution.

Leitz, Karl-Heinz; Tsai, Yu-Cheng; Flad, Florian; Schäffer, Eike; Quentin, Ulf; Alexeev, Ilya; Fardel, Romain; Arnold, Craig B.; Schmidt, Michael

2013-06-01

220

Multiphoton coherent control in complex systems  

PubMed Central

Control of multiphoton transitions is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion while the even terms lead to self-induced transparency. The results hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse width. PMID:17396157

Goswami, Debabrata

2005-01-01

221

Multiphoton ionization/dissociation of cyclopentanone at the lower Rydberg states  

SciTech Connect

The 2-photon excitation of the 3p and 3d Rydberg states in jet-cooled cyclopentanone has been investigated by resonance enhanced multiphoton ionization (REMPI) in a time of flight mass spectrometer. The three 3p{sub x,y,z} components are clearly resolved while the case for the 3d{sub i} excitations is obscure due to the S{sub 1} one-photon resonance. The ns laser induced mass spectra are characteristic of hard ionization while the fs laser induced mass spectrum is very similar to the Electron Impact one.

Philis, John G.; Kosmidis, Constantine; Tzallas, Paraskevas [Department of Physics, University of Ioannina, GR45110 Ioannina (Greece)

1998-12-16

222

Multiphoton ionization/dissociation of cyclopentanone at the lower Rydberg states  

NASA Astrophysics Data System (ADS)

The 2-photon excitation of the 3p and 3d Rydberg states in jet-cooled cyclopentanone has been investigated by resonance enhanced multiphoton ionization (REMPI) in a time of flight mass spectrometer. The three 3px,y,z components are clearly resolved while the case for the 3di excitations is obscure due to the S1 one-photon resonance. The ns laser induced mass spectra are characteristic of hard ionization while the fs laser induced mass spectrum is very similar to the Electron Impact one.

Philis, John G.; Kosmidis, Constantine; Tzallas, Paraskevas

1998-12-01

223

Excitation mechanism of blue anti-Stokes and 2.4 ?m infrared emission in ZnSe : Cr  

Microsoft Academic Search

We report the observation and analyze the mechanism of efficient blue anti-Stokes emission in ZnSe:Cr. This emission and the intra-shell transition of chromium Cr2+ at 2.4?m are induced by 2+?1+ ionization transition of chromium ions in ZnSe:Cr. The efficiency of the anti-Stokes photoluminescence anticorrelates with the efficiency of the infrared emission. The latter emission dominates at increased temperatures. We conclude

V. Yu. Ivanov; A. A. Shagov; A. Szczerbakow; M. Godlewski

2001-01-01

224

Characterization of human normal and cancerous gastric submucosa based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Gastric cancer is one of the most frequent cancers in the world; almost two-thirds of gastric cancer cases and deaths occur in less developed regions. The initial diagnosis of gastric cancer often is delayed because up to 80 percent of patients are asymptomatic during the early stages of stomach cancer. So the ability to perform real-time in vivo histological diagnosis for early gastric cancer at the cellular level during ongoing endoscopy is a long-standing goal of endoscopists. In this paper, using multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG), MPM images of human normal and cancerous gastric submucosa were obtained at excitation wavelength of 800 nm. The features such as the appearance of abnormal cells and the large loss of collagen in cancerous gastric submucosa were extracted to be as significant indicators to distinguish cancerous submucosa from normal submucosa. With the implementation of multiphoton microscopy concept in endoscopy applications, multiphoton endoscopy might realize in vivo histological diagnosis goal of endoscopists.

Zhong, Jiazhao; Chen, G.; Liu, Y. C.; Zhuo, S. M.; Chen, J. X.; Yan, J.

2011-11-01

225

Characterization of human normal and cancerous gastric submucosa based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Gastric cancer is one of the most frequent cancers in the world; almost two-thirds of gastric cancer cases and deaths occur in less developed regions. The initial diagnosis of gastric cancer often is delayed because up to 80 percent of patients are asymptomatic during the early stages of stomach cancer. So the ability to perform real-time in vivo histological diagnosis for early gastric cancer at the cellular level during ongoing endoscopy is a long-standing goal of endoscopists. In this paper, using multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG), MPM images of human normal and cancerous gastric submucosa were obtained at excitation wavelength of 800 nm. The features such as the appearance of abnormal cells and the large loss of collagen in cancerous gastric submucosa were extracted to be as significant indicators to distinguish cancerous submucosa from normal submucosa. With the implementation of multiphoton microscopy concept in endoscopy applications, multiphoton endoscopy might realize in vivo histological diagnosis goal of endoscopists.

Zhong, Jiazhao; Chen, G.; Liu, Y. C.; Zhuo, S. M.; Chen, J. X.; Yan, J.

2012-03-01

226

Near-infrared photopolymerization: Initiation process assisted by self-quenching and triplet-triplet annihilation of excited cyanine dyes  

NASA Astrophysics Data System (ADS)

The mechanism of radical polymerization photoinitiated by a near-infrared absorbing indotricarbocyanine (HITC) was investigated using an indirect kinetics method based on the photobleaching dynamics of the dye. Despite similar photophysical features in glycerol and in pentaerythritol triacrylate monomer, HITC undergoes a very fast photobleaching in the acrylate resin which leads to photopolymerization at high power regime. The addition of an amine induces the decrease of photopolymerization threshold by a factor 5 with unexpected dye regeneration. These effects were correlated to the reactivity of the reduced and oxidized forms of HITC produced via triplet-triplet annihilation and ground state quenching processes.

Dika, Ihab; Malval, Jean-Pierre; Soppera, Olivier; Bardinal, Véronique; Barat, David; Turck, Colette; Spangenberg, Arnaud; Bruyant, Aurélien

2011-10-01

227

Soliton dynamics in the multiphoton plasma regime  

E-print Network

Soliton dynamics in the multiphoton plasma regime Chad A. Husko1 *, Sylvain Combrie´2 , Pierre, to gap solitons for dispersionless slow-light, and discrete spatial solitons in lattices, amongst others W/cm2 . Here we report the first phase-resolved observations of femtosecond optical solitons

Hone, James

228

Route to direct multiphoton multiple ionization  

SciTech Connect

We address the concept of direct multiphoton multiple ionization in atoms exposed to intense, short-wavelength radiation and explore the conditions under which such processes dominate over the sequential. Their contribution is shown to be quite robust, even under intensity fluctuations and interaction volume integration, and reasonable agreement with experimental data is also found.

Lambropoulos, P. [Institute of Electronic Structure and Laser, FORTH, P.O. Box 1527, GR-71110 Heraklion (Greece); Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete (Greece); Kavli Institute for Theoretical Physics, Santa Barbara, California 93106 (United States); Nikolopoulos, G. M. [Institute of Electronic Structure and Laser, FORTH, P.O. Box 1527, GR-71110 Heraklion (Greece); Kavli Institute for Theoretical Physics, Santa Barbara, California 93106 (United States); Papamihail, K. G. [Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete (Greece)

2011-02-15

229

Potential role of silanones in the photoluminescence-excitation, visible-photoluminescence-emission, and infrared spectra of porous silicon  

NASA Astrophysics Data System (ADS)

Ab initio molecular electronic structure calculations on select silanones, silylenes, and tricoordinated silicon compounds SiXYZ with a dangling electron are presented. The calculations are used to evaluate the nature of the electronic spectra, which are to be associated with surface-bound Si/O/H compounds. In concert, they are used to suggest an explanation for the nature of the photoluminescence-excitation spectrum (PLE) and the subsequent visible luminescence (PL) from porous silicon (PS) based on the optical properties of the silanone-based oxyhydrides. In order to make this selection, we treat a set of compounds that includes the silanones Si(O)H2, Si(O)H(OH), Si(O)(OH)2, Si(O)H(OSiH3), Si(O)H(SiH3), Si(O)(OH)(SiH3), Si(O)(SiH3)2, and Si(O)(SiH3)(OSiH3), the silylenes HSiOH, HOSiOH, and HOSiOSiH3, and the tricoordinated silicon compounds SiH3, Si(OH)H2, Si(OH)2H, and Si(OH)3. The silanone-based oxyhydride structures containing either an OH or OSiH3 group all display adiabatic ground-state singlet-excited-state triplet exciton separations in the range close to 400 nm. This adiabatic energy is consistent with the vertical transition energies associated with the PS excitation spectrum (PLE) as a large change in the Si=O bond distance (~0.17 Å) accompanies the transition from the silanone ground electronic singlet state to the low-lying triplet exciton (or its closely lying singlet coupled configuration). The maximum in the PLE spectrum, obtained through optical pumping from the lowest vibrational levels of the ground electronic state to considerably higher levels of the triplet exciton electronic state, should therefore be shifted to considerably shorter wavelength consistent with an absorption spectrum peaking at 350 nm as observed by several researchers. A shift to larger internuclear distance in the excited-state triplet exciton will also produce a considerable redshift in the PL emission spectrum relative to the absorption-excitation wavelengths, again consistent with experimental observation. The calculated IR spectra for the silanone-based oxyhydrides are also consistent with the observed Fourier transform IR spectra of porous silicon. In clear contrast, neither the silylenes nor the tricoordinated silicon compounds with dangling electrons can account for the excitation or emission features that are associated with PS as their lowest-lying transitions result in minimal changes in bonding and/or occur at much higher energy (shorter wavelength). The results obtained in this study also suggest that surface passivation or the saturation of valency is incommensurate with the formation of the fluorophors that will produce the emission from PS.

Gole, James L.; Dixon, David A.

1998-05-01

230

Studies of atmospheric molecules by multiphoton spectroscopy. Progress report, July 15, 1989--October, 1991  

SciTech Connect

Carbon dioxide presents a great challenge to spectroscopy because of its propensity toward dissociation in all of its excited states. Multiphoton ionization spectroscopy is usually not applicable to the study of dissociating molecules because the dissociation competes effectively with ionization, resulting in no signal. We reasoned, however, that with high enough laser fluence, ionization could compete with dissociation in the longer lived states, exposing them for study from the continuous spectral background resulting from rapidly dissociating states. We describe the various spectroscopic and photophysical effects found through the multiphoton ionization and multiphoton photoelectron spectra. A recently developed variant of threshold ionization spectroscopy, usually called ZEKE, has shown a great deal of usefulness in providing the same information as traditional photoelectron spectroscopy but with higher resolution and much better signal-to-noise when using standard laboratory lasers. Threshold ionization techniques locate the states of an ion by scanning a light source across the ionization continuum of a neutral and somehow detecting when electrons are produced with no kinetic energy. We chose to develop our capabilities in threshold ionization spectroscopy using aromatic molecules because of their importance and because their electronic structure allows a pump-probe type of excitation scheme which avoids the use of vacuum ultraviolet laser beams. Among aromatics, the azines are noted for their small S{sub 1}-T{sub 1} energy gap which give them unique and interesting photophysical properties. We have continued our work on the multiphoton spectrum of metastable nitrogen produced by an electric discharge in supersonic beam. We have been able to assign more of the lines and simulated their rotational structure but many peaks remain unassigned.

Johnson, P.M.

1991-10-01

231

Plasmon-mediated generation of reactive oxygen species from near-infrared light excited gold nanocages for photodynamic therapy in vitro.  

PubMed

We have performed fundamental assays of gold nanocages (AuNCs) as intrinsic inorganic photosensitizers mediating generation of reactive oxygen species (ROS) by plasmon-enabled photochemistry under near-infrared (NIR) one/two-photon irradiation. We disclosed that NIR light excited hot electrons transform into either ROS or hyperthermia. Electron spin resonance spectroscopy was applied to demonstrate the production of three main radical species, namely, singlet oxygen ((1)O2), superoxide radical anion (O2(-•)), and hydroxyl radical ((•)OH). The existence of hot electrons from irradiated AuNCs was confirmed by a well-designed photoelectrochemical experiment based on a three-electrode system. It could be speculated that surface plasmons excited in AuNCs first decay into hot electrons, and then the generated hot electrons sensitize oxygen to form ROS through energy and electron transfer modes. We also compared AuNCs' ROS generation efficiency in different surface chemical environments under one/two-photon irradiation and verified that, compared with one-photon irradiation, two-photon irradiation could bring about much more ROS. Furthermore, in vitro, under two-photon irradiation, ROS can trigger mitochondrial depolarization and caspase protein up-regulation to initiate tumor cell apoptosis. Meanwhile, hyperthermia mainly induces tumor cell necrosis. Our findings suggest that plasmon-mediated ROS and hyperthermia can be facilely regulated for optimized anticancer phototherapy. PMID:24992260

Gao, Liang; Liu, Ru; Gao, Fuping; Wang, Yaling; Jiang, Xinglu; Gao, Xueyun

2014-07-22

232

Infrared photodissociation of a water molecule from a flexible molecule-H2O complex: Rates and conformational product yields following XH stretch excitation  

NASA Astrophysics Data System (ADS)

Infrared-ultraviolet hole-burning and hole-filling spectroscopies have been used to study IR-induced dissociation of the tryptamine•H2O and tryptamine•D2O complexes. Upon complexation of a single water molecule, the seven conformational isomers of tryptamine collapse to a single structure that retains the same ethylamine side chain conformation present in the most highly populated conformer of tryptamine monomer. Infrared excitation of the tryptamine•H2O complex was carried out using a series of infrared absorptions spanning the range of 2470-3715cm-1. The authors have determined the conformational product yield over this range and the dissociation rate near threshold, where it is slow enough to be measured by our methods. The observed threshold for dissociation occurred at 2872cm-1 in tryptamine•H2O and at 2869cm-1 in tryptamine•D2O, with no dissociation occurring on the time scale of the experiment (˜2?s) at 2745cm-1. The dissociation time constants varied from ˜200ns for the 2869cm-1 band of tryptamine•D2O to ˜25ns for the 2872cm-1 band of tryptamine•H2O. This large isotope dependence is associated with a zero-point energy effect that increases the binding energy of the deuterated complex by ˜190cm-1, thereby reducing the excess energy available at the same excitation energy. At all higher energies, the dissociation lifetime was shorter than the pulse duration of our lasers (8ns). At all wavelengths, the observed products in the presence of collisions are dominated by conformers A and B of tryptamine monomer, with small contributions from the other minor conformers. In addition, right at threshold (2869cm-1), tryptamine•D2O dissociates exclusively to conformer A in the absence of collisions with helium, while both A and B conformational products are observed in the presence of collisions with helium. Using resolution-of-identity approximation to second-order Møller-Plesset binding energies extrapolated to the complete basis set limit and harmonic vibrational frequencies and transition states calculated at the density functional limit B3LYP /6-31+G* level of theory, Rice-Ramsperger-Kassel-Marcus (RRKM) predictions for the dissociation, isomerization, and water shuttling rates as a function of energy are made. At threshold, the experimental dissociation rate is almost 103 faster than RRKM predictions. Reasons for this apparent non-RRKM behavior will be discussed.

Clarkson, Jasper R.; Herbert, John M.; Zwier, Timothy S.

2007-04-01

233

Infrared photodissociation of a water molecule from a flexible molecule-H2O complex: rates and conformational product yields following XH stretch excitation.  

PubMed

Infrared-ultraviolet hole-burning and hole-filling spectroscopies have been used to study IR-induced dissociation of the tryptamine.H2O and tryptamine.D2O complexes. Upon complexation of a single water molecule, the seven conformational isomers of tryptamine collapse to a single structure that retains the same ethylamine side chain conformation present in the most highly populated conformer of tryptamine monomer. Infrared excitation of the tryptamine.H2O complex was carried out using a series of infrared absorptions spanning the range of 2470-3715 cm-1. The authors have determined the conformational product yield over this range and the dissociation rate near threshold, where it is slow enough to be measured by our methods. The observed threshold for dissociation occurred at 2872 cm-1 in tryptamine.H2O and at 2869 cm-1 in tryptamine.D2O, with no dissociation occurring on the time scale of the experiment (approximately 2 micros) at 2745 cm-1. The dissociation time constants varied from approximately 200 ns for the 2869 cm-1 band of tryptamine.D2O to approximately 25 ns for the 2872 cm-1 band of tryptamine.H2O. This large isotope dependence is associated with a zero-point energy effect that increases the binding energy of the deuterated complex by approximately 190 cm-1, thereby reducing the excess energy available at the same excitation energy. At all higher energies, the dissociation lifetime was shorter than the pulse duration of our lasers (8 ns). At all wavelengths, the observed products in the presence of collisions are dominated by conformers A and B of tryptamine monomer, with small contributions from the other minor conformers. In addition, right at threshold (2869 cm-1), tryptamine.D2O dissociates exclusively to conformer A in the absence of collisions with helium, while both A and B conformational products are observed in the presence of collisions with helium. Using resolution-of-identity approximation to second-order Moller-Plesset binding energies extrapolated to the complete basis set limit and harmonic vibrational frequencies and transition states calculated at the density functional limit B3LYP/6-31+G* level of theory, Rice-Ramsperger-Kassel-Marcus (RRKM) predictions for the dissociation, isomerization, and water shuttling rates as a function of energy are made. At threshold, the experimental dissociation rate is almost 10(3) faster than RRKM predictions. Reasons for this apparent non-RRKM behavior will be discussed. PMID:17430031

Clarkson, Jasper R; Herbert, John M; Zwier, Timothy S

2007-04-01

234

Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized pseudospectral method  

E-print Network

with wavelengths from visible lights (4×102 nm) to infrared radiations (1×105 nm). With the recent development of intense and ultrashort-wavelength free-electron lasers [32–34], the study of multiphoton *zyzhou@ku.edu †sichu@ku.edu processes in the high...

Chu, Shih-I; Zhou, Zhongyuan

2011-01-19

235

Simulated infrared emission spectra of highly excited polyatomic molecules: a detailed model of the PAH-UIR hypothesis  

NASA Technical Reports Server (NTRS)

A detailed description of the polycyclic aromatic hydrocarbon (PAH)/unidentified infrared band (UIR) mechanism is presented in which experimental spectral bandshape functions are used to simulate IR emission spectra for individual molecules. These spectra are additively superimposed to produce a conglomerate spectrum representative of a family of PAH molecules. Ab initio vibrational frequencies and intensities for nine PAHs (neutral and cationic) as large as ovalene are used in conjunction with measured bandshape and temperature-dependent redshift data to simulate the UIR bands. The calculated spectra of cations provide a closer match to the UIRs than do those of the neutrals. However, the PAH cations used in the simulations fail to reproduce the details of the UIR emission spectra. The discrepancies are potentially alleviated if both larger PAHs and a greater number of PAHs were included in the simulation.

Cook, D. J.; Saykally, R. J.

1998-01-01

236

Collision dynamics of methyl radicals and highly vibrationally excited molecules using crossed molecular beams  

SciTech Connect

The vibrational to translational (V{yields}T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V{yields}T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH{sub 3} production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.

Chu, P.M.Y.

1991-10-01

237

Influence of solvent contribution on nonlinearities of near infra-red absorbing croconate and squaraine dyes with ultrafast laser excitation  

NASA Astrophysics Data System (ADS)

Third order optical nonlinearities of various solvents such as Dimethylformamide (DMF), ethanol, chloroform, CCl4, acetone, toluene, Tetrahydrofuran (THF), and CS2 are studied in picosecond (ps) and femtosecond (fs) time scales using Z-scan technique. All the solvents show reverse saturable absorption behavior which is attributed to significant two-photon absorption and three-photon absorption processes in ps and fs time scale regimes, respectively. Nonlinear refraction studies reveal the positive signature of nonlinearity of solvents in both pulse regimes. We have investigated the effect of solvents on observed nonlinearities of near infra-red absorbing squaraine and croconate dye samples. Interestingly, a change in the sign of nonlinearity of molecules (phe cro, ptbu cro, phe squ, and ptbu squ) is observed in the ps regime when the solvent contribution is removed. Further, we also observed a change in magnitude of the nonlinearity for all the molecules under both pulse regimes. This gives clear evidence on the role of the solvents in the measurement of optical nonlinearities and that the true nonlinearities of the solute in fs/ps time domain can only be obtained when the measurements account for the solvent.

Bala Murali Krishna, M.; Narayana Rao, D.

2013-10-01

238

Contrast ratio and separation factor in multiphoton dissociation of supercooled UF6 irradiated with multifrequency 16 ?m Raman-laser radiation  

NASA Astrophysics Data System (ADS)

In infrared multiphoton dissociation of supercooled UF6 irradiated with multifrequency para-H2 Raman laser beams, separation factors and contrast ratios were measured by selective multiphoton ionization of the photoproduct UF5 at 532 nm followed by time-of-flight mass spectrometric analysis. The relationship between separation factor and contrast ratio is discussed theoretically and quantitatively investigated in the experiments. From this relationship, we obtain the irradiation conditions of the laser-beam fluences for attaining a high separation factor and estimate the value of the intrinsic separation factor in multifrequency dissociation of UF6.

Okada, Y.; Kato, S.; Sunouchi, K.; Satooka, S.; Tashiro, H.; Takeuchi, K.

1996-01-01

239

Multiphoton Imaging of Upconverting Lanthanide Nanoparticles in Three Dimensional Models of Cancer  

PubMed Central

While upconverting lanthanide nanoparticles have numerous advantages over other exogenous contrast agents used in scanned multiphoton imaging, their long luminescence lifetimes cause images collected with non-descanned detection to be greatly blurred. We demonstrate herein the use of Richardson-Lucy deconvolution to deblur luminescence images obtained via multiphoton scanning microscopy. Images were taken of three dimensional models of colon and ovarian cancer following incubation with NaYF4:Yb,Er nanoparticles functionalized with an antibody for EGFR and folic acid respectively. Following deconvolution, images had a lateral resolution on par with the optimal performance of the imaging system used, ~1.2 ?m, and an axial resolution of ~5 ?m. Due to the relatively high multiphoton excitation efficiency of these nanoparticles, it is possible to follow binding of individual particles in tissue. In addition, their extreme photostability allows for prolonged imaging without significant loss in luminescence signal. With these advantageous properties in mind, we also discuss the potential application of upconverting lanthanide nanoparticles for tracking of specific, cancer relevant receptors in tissue. PMID:24353385

Gainer, Christian F.; Romanowski, Marek

2013-01-01

240

Multiphoton imaging of upconverting lanthanide nanoparticles in three dimensional models of cancer  

NASA Astrophysics Data System (ADS)

While upconverting lanthanide nanoparticles have numerous advantages over other exogenous contrast agents used in scanned multiphoton imaging, their long luminescence lifetimes cause images collected with non-descanned detection to be greatly blurred. We demonstrate herein the use of Richardson-Lucy deconvolution to deblur luminescence images obtained via multiphoton scanning microscopy. Images were taken of three dimensional models of colon and ovarian cancer following incubation with NaYF4:Yb,Er nanoparticles functionalized with an antibody for EGFR and folic acid respectively. Following deconvolution, images had a lateral resolution on par with the optimal performance of the imaging system used, ~1.2 ?m, and an axial resolution of ~5 ?m. Due to the relatively high multiphoton excitation efficiency of these nanoparticles, it is possible to follow binding of individual particles in tissue. In addition, their extreme photostability allows for prolonged imaging without significant loss in luminescence signal. With these advantageous properties in mind, we also discuss the potential application of upconverting lanthanide nanoparticles for tracking of specific, cancer relevant receptors in tissue.

Gainer, Christian F.; Romanowski, Marek

2013-02-01

241

Clinical optical coherence tomography combined with multiphoton tomography for evaluation of several skin disorders  

NASA Astrophysics Data System (ADS)

The first clinical trial of optical coherence tomography (OCT) combined with multiphoton tomography (MPT) and dermoscopy is reported. State-of-the-art (i) OCT systems for dermatology (e.g. multibeam swept source OCT), (ii) the femtosecond laser multiphoton tomograph DermaInspectTM, and (iii) digital dermoscopes were applied to 47 patients with a diversity of skin diseases and disorders such as skin cancer, psoriasis, hemangioma, connective tissue diseases, pigmented lesions, and autoimmune bullous skin diseases. Dermoscopy, also called 'epiluminescent microscopy', provides two-dimensional color images of the skin surface. OCT imaging is based on the detection of optical reflections within the tissue measured interferometrically whereas nonlinear excitation of endogenous fluorophores and the second harmonic generation are the bases of MPT images. OCT cross sectional "wide field" image provides a typical field of view of 5 x 2 mm2 and offers fast information on the depth and the volume of the investigated lesion. In comparison, multiphoton tomography presents 0.36 x 0.36 mm2 horizontal or diagonal sections of the region of interest within seconds with submicron resolution and down to a tissue depth of 200 ?m. The combination of OCT and MPT provides a synergistic optical imaging modality for early detection of skin cancer and other skin diseases.

König, Karsten; Speicher, Marco; Bückle, Rainer; Reckfort, Julia; McKenzie, Gordon; Welzel, Julia; Koehler, Martin J.; Elsner, Peter; Kaatz, Martin

2010-02-01

242

In vivo multiphoton imaging of collagen remodeling after microablative fractional rejuvenation  

NASA Astrophysics Data System (ADS)

The potential of multiphoton microscopy in providing in-vivo early diagnosis of skin lesions has already been demonstrated, while its capability in therapy follow-up has not been deeply explored so far. Two-photon excited fluorescence and second-harmonic generation microscopy were used in combination to follow-up collagen remodeling after laser micro-ablative rejuvenation. Treated regions of volunteers were imaged with multiphoton microscopy before and after treatment, and we found a strong age-dependence of the treatment effectiveness. In particular, the photorejuvenating effect was negligible in young subjects (< 30 years), whereas a significant production of new collagen was observed in aged subjects (> 70 years). Quantification of the amount of newly produced collagen and its organization were performed by means of visual examination of two-photon images. The obtained results demonstrate the performance of laser fractional micro-ablative rejuvenation without the need of an invasive biopsy as well as the wide applicability range of applications for multiphoton microscopy in clinical dermatology.

Cicchi, Riccardo; Kapsokalyvas, Dimitrios; Troiano, Michela; Campolmi, Piero; Morini, Cristiano; Cosci, Alessandro; Massi, Daniela; Lotti, Torello; Pavone, Francesco S.

2011-03-01

243

Intrinsic Indicator of Photodamage during Label-Free Multiphoton Microscopy of Cells and Tissues  

PubMed Central

Multiphoton imaging has evolved as an indispensable tool in cell biology and holds prospects for clinical applications. When addressing endogenous signals such as coherent anti-Stokes Raman scattering (CARS) or second harmonic generation, it requires intense laser irradiation that may cause photodamage. We report that increasing endogenous fluorescence signal upon multiphoton imaging constitutes a marker of photodamage. The effect was studied on mouse brain in vivo and ex vivo, on ex vivo human brain tissue samples, as well as on glioblastoma cells in vitro, demonstrating that this phenomenon is common to a variety of different systems, both ex vivo and in vivo. CARS microscopy and vibrational spectroscopy were used to analyze the photodamage. The development of a standard easy-to-use model that employs rehydrated cryosections allowed the characterization of the irradiation-induced fluorescence and related it to nonlinear photodamage. In conclusion, the monitoring of endogenous two-photon excited fluorescence during label-free multiphoton microscopy enables to estimate damage thresholds ex vivo as well as detect photodamage during in vivo experiments. PMID:25343251

Andresen, Elisabeth F.; Geiger, Kathrin D.; Koch, Edmund; Schackert, Gabriele; Steiner, Gerald; Kirsch, Matthias

2014-01-01

244

Multiphoton Imaging of Renal Regulatory Mechanisms  

NSDL National Science Digital Library

Most physiological functions of the kidneys, including the clearance of metabolic waste products, maintenance of body fluid, electrolyte homeostasis, and blood pressure, are achieved by complex interactions between multiple renal cell types and previously inaccessible structures in many organ parts that have been difficult to study. Multiphoton fluorescence microscopy offers a state-of-the-art imaging technique for deep optical sectioning of living tissues and organs with minimal deleterious effects. Dynamic regulatory processes and multiple functions in the intact kidney can be quantitatively visualized in real time, noninvasively, and with submicron resolution. This article reviews innovative multiphoton imaging technologies and their applications that provided the most complex, immediate, and dynamic portrayal of renal functionÃÂclearly depicting as well as analyzing the components and mechanisms involved in renal (patho)physiology.

Janos Peti-Peterdi (Departments of Physiology and Biophysics and Medicine); Ildiko Toma (University of Southern California); Arnold Sipos (University of Souther California); Sarah Vargas (University of California)

2009-04-01

245

Multi-photon states and their measurement  

Microsoft Academic Search

Generation of multi-photon states (such as for instance three- and four-photon states) is one of the most challenging problems of modern quantum optics. In many works the authors claim to have produced such states by means of overlapping photon pairs generated in spontaneous parametric down-conversion (SPDC). Moreover three- and four-photon states generated this way have been used for observing Greenberger-Horne-Zeilinger

T. S. Iskhakov; O. A. Ivanova; Maria V. Chekhova

2005-01-01

246

Medium-induced multi-photon radiation  

E-print Network

We study the spectrum of multi-photon radiation off a fast quark in medium in the BDMPS/ASW approach. We reproduce the medium-induced one-photon radiation spectrum in dipole approximation, and go on to calculate the two-photon radiation in the Moli\\`{e}re limit. We find that in this limit the LPM effect holds for medium-induced two-photon ladder emission.

Hao Ma; Carlos A. Salgado; Konrad Tywoniuk

2011-05-29

247

Unimolecular fragmentation kinetics by multiphoton ionization  

NASA Astrophysics Data System (ADS)

The multiphoton ionization spectrum of aniline and its perdeutero analog have been investigated for laser wavelenghts 266-300 nm using a time-of-flight mass spectrometer. A brod, asymmetrically distorted peak of m/ e = 66 is interpreted to be the slow fragmentation of the parent ion, C 6H 7N + ? C 5H 6+ + HCN; its unimolecular decomposition rate is ? 2 × 10 6 s -1.

Proch, D.; Rider, D. M.; Zare, R. N.

1981-08-01

248

Collective Excitation of Rydberg-Atom Ensembles beyond the Superatom Model  

NASA Astrophysics Data System (ADS)

In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the steady-state excitation probability is usually substantially suppressed. In contrast, here we identify a regime in which the Rydberg excited fraction is enhanced by the interaction. This effect is associated with the buildup of many-body coherences induced by coherent multiphoton excitations between collective states. The excitation enhancement should be observable under currently existing experimental conditions and may serve as a direct probe for the presence of coherent multiphoton dynamics involving collective quantum states.

Gärttner, Martin; Whitlock, Shannon; Schönleber, David W.; Evers, Jörg

2014-12-01

249

Collective Excitation of Rydberg-Atom Ensembles beyond the Superatom Model.  

PubMed

In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the steady-state excitation probability is usually substantially suppressed. In contrast, here we identify a regime in which the Rydberg excited fraction is enhanced by the interaction. This effect is associated with the buildup of many-body coherences induced by coherent multiphoton excitations between collective states. The excitation enhancement should be observable under currently existing experimental conditions and may serve as a direct probe for the presence of coherent multiphoton dynamics involving collective quantum states. PMID:25526126

Gärttner, Martin; Whitlock, Shannon; Schönleber, David W; Evers, Jörg

2014-12-01

250

T\\/D isotope selectivity in CO2 laser induced multiple-frequency multiphoton dissociation of trifluoromethane-T  

Microsoft Academic Search

Isotope-selective multiphoton dissociation of CTF3 in the presence of CDF3 by TEA CO2 laser is studied. The highest T\\/D selectivity of 58 was observed at a sample pressure of 2 Torr in the presence of 20 Torr of argon on excitation by the 9 P(24) CO2 laser line. The effect of multiple-frequency irradiation on selectivity is studied in the P

A. K. Nayak; R. S. Karve; S. K. Sarkar; K. V. S. Rama Rao; J. P. Mittal

1989-01-01

251

Infrared-active optical phonons and magnetic excitations in the hexagonal manganites RMnO3 (R =Ho, Er, Tm, Yb, and Lu)  

NASA Astrophysics Data System (ADS)

Optical properties of hexagonal multiferroic oxides RMnO3, where R=Ho, Er, Tm, Yb, and Lu, have been studied in the far-infrared spectral range between 100 and 2000 cm-1 and temperatures between 1.5 and 300 K by means of several experimental techniques: Mueller matrix spectroscopic ellipsometry, rotating analyzer ellipsometry, and optical transmission spectroscopy. Spectra of the optical phonons are described in terms of the temperature dependencies of their frequency, damping, and oscillator strength. For all studies, oxide materials' clear signatures of the spin-phonon interaction have been found below the temperature of the antiferromagnetic phase transition TN due to magnetic ordering of Mn3+ spins. A decrease of the ionic radius for R3+ ions between Ho3+ and Lu3+ in the corresponding RMnO3 compounds resulted in systematic variation of the frequency for several optical phonons. A magnetic excitation at ˜190 cm-1 was observed at low temperatures below TN and interpreted as resulting from two-magnon absorption.

Basistyy, R.; Stanislavchuk, T. N.; Sirenko, A. A.; Litvinchuk, A. P.; Kotelyanskii, M.; Carr, G. L.; Lee, N.; Wang, X.; Cheong, S.-W.

2014-07-01

252

Organic matter humification in vermifiltration process for domestic sewage sludge treatment by excitation-emission matrix fluorescence and Fourier transform infrared spectroscopy.  

PubMed

Performance of a conventional biofilter (BF) and two vermifilters (VFs, different heights) containing earthworms was investigated for domestic sewage sludge (DWS) treatment. Humic-acid like (HAL) fraction isolated from the influent sludge (IS) and effluent sludge of BF (ESBF) and VFs (ESVFs) were determined the elemental and functional composition, and structural characteristics using various analytical approaches. Results showed that performance of DWS treatment in the VFs was preferable to that in the BF. With respect to IS-HAL and ESBF-HAL, ESVFs-HAL had low C, H and N contents and C/O ratio, and high O, carboxyl and phenolic OH group contents, and C/N, C/H and E4/E6 ratios, and large molecular weight. The excitation-emission (Ex/Em) matrix spectra revealed that an additional peak was found at Ex/Em wavelength pairs of 345/435 nm in ESVFs-HAL. Further, Fourier transform infrared spectra showed that vermifiltration led to the loss of aliphatic materials and carbohydrates, and the enrichment of carbonyl and phenolic OH groups in HAL fractions. Additionally, the increase in VF height seemed to accelerate humification degree of organic matter in the effluent sludge. In summary, vermifiltration is alternate technology for transformation of organic matter into humic substances, and thus improves quality of DWS as soil organic fertilizer. PMID:23981770

Li, Xiaowei; Xing, Meiyan; Yang, Jian; Zhao, Limin; Dai, Xiaohu

2013-10-15

253

Time-resolved study of rotational and vibrational excitation and relaxation in the /sup 13/CH/sub 3/F optically pumped far-infrared laser  

SciTech Connect

The rotational and vibrational energy-transfer processes of the CH/sub 3/F optically pumped far-infrared (OPFIR) laser were studied in a time-resolved experiment. The experiment uses a tunable millimeter and submillimeter spectroscopic technique as a diagnostic probe. Included are observations of the fast Delta J processes that closely connect other J states with K = 3 to the directly pumped J = 5 level, a vibrational swapping mechanism that transfers excitation from K = 3 to other K states, vibrational relaxation due to both wall collisions and molecule-molecule collisions, the nonunity probability of vibrational deactivation in a wall collision, and pump saturation and hole-burning effects due to the CO/sub 2/ pump laser. All of these observations are accounted for in the context of a numerical simulation. This results in a complete map of all of the collision-induced rotation/vibration transitions of importance to this basic OPFIR system including quantitative cross sections for the relevant processes.

McCormick, R.I.; De Lucia, F.C.; Skatrud, D.D.

1987-12-01

254

High-resolution fluorescence microscopy based on a cyclic sequential multiphoton process  

PubMed Central

We demonstrate high-resolution fluorescence microscopy based on a cyclic sequential multiphoton (CSM) process, which gives rise to fluorescence emission following a sequence of cyclic transitions between the bright and dark states of a fluorophore induced by pump and reverse light. By temporally modulating the reverse intensity, we can extract the fluorescence signal generated through the CSM process. We show that the demodulated fluorescence signal is nonlinearly proportional to the excitation intensities and it gives a higher spatial resolution than that of a confocal microscope. PMID:21258510

Isobe, Keisuke; Suda, Akira; Hashimoto, Hiroshi; Kannari, Fumihiko; Kawano, Hiroyuki; Mizuno, Hideaki; Miyawaki, Atsushi; Midorikawa, Katsumi

2010-01-01

255

Identification of dirty necrosis in colorectal carcinoma based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Dirty necrosis within glandular lumina is often considered as a characteristic of colorectal carcinomas (CRCs) that is a diagnostically useful feature of CRCs with DNA microsatellite instability (MSI). Multiphoton microscopy (MPM), which is based on the second-harmonic generation and two-photon excited fluorescence signals, was used to identify dirty necrosis. Our results demonstrated that MPM has the ability to exhibit the microstructure of dirty necrosis and the signal intensity as well as an emission spectrum that can help to differentiate dirty necrosis from cancer cells. These findings indicate that MPM may be helpful in distinguishing MSI colorectal carcinoma via the identification of dirty necrosis.

Li, Lianhuang; Jiang, Weizhong; Yang, Yinghong; Chen, Zhifen; Feng, Changyin; Li, Hongsheng; Guan, Guoxian; Chen, Jianxin

2014-06-01

256

Infrared photodissociation of a water molecule from a flexible molecule-H{sub 2}O complex: Rates and conformational product yields following XH stretch excitation  

SciTech Connect

Infrared-ultraviolet hole-burning and hole-filling spectroscopies have been used to study IR-induced dissociation of the tryptamine{center_dot}H{sub 2}O and tryptamine{center_dot}D{sub 2}O complexes. Upon complexation of a single water molecule, the seven conformational isomers of tryptamine collapse to a single structure that retains the same ethylamine side chain conformation present in the most highly populated conformer of tryptamine monomer. Infrared excitation of the tryptamine{center_dot}H{sub 2}O complex was carried out using a series of infrared absorptions spanning the range of 2470-3715 cm{sup -1}. The authors have determined the conformational product yield over this range and the dissociation rate near threshold, where it is slow enough to be measured by our methods. The observed threshold for dissociation occurred at 2872 cm{sup -1} in tryptamine{center_dot}H{sub 2}O and at 2869 cm{sup -1} in tryptamine{center_dot}D{sub 2}O, with no dissociation occurring on the time scale of the experiment ({approx}2 {mu}s) at 2745 cm{sup -1}. The dissociation time constants varied from {approx}200 ns for the 2869 cm{sup -1} band of tryptamine{center_dot}D{sub 2}O to {approx}25 ns for the 2872 cm{sup -1} band of tryptamine{center_dot}H{sub 2}O. This large isotope dependence is associated with a zero-point energy effect that increases the binding energy of the deuterated complex by {approx}190 cm{sup -1}, thereby reducing the excess energy available at the same excitation energy. At all higher energies, the dissociation lifetime was shorter than the pulse duration of our lasers (8 ns). At all wavelengths, the observed products in the presence of collisions are dominated by conformers A and B of tryptamine monomer, with small contributions from the other minor conformers. In addition, right at threshold (2869 cm{sup -1}), tryptamine{center_dot}D{sub 2}O dissociates exclusively to conformer A in the absence of collisions with helium, while both A and B conformational products are observed in the presence of collisions with helium. Using resolution-of-identity approximation to second-order Moeller-Plesset binding energies extrapolated to the complete basis set limit and harmonic vibrational frequencies and transition states calculated at the density functional limit B3LYP/6-31+G{sup *} level of theory, Rice-Ramsperger-Kassel-Marcus (RRKM) predictions for the dissociation, isomerization, and water shuttling rates as a function of energy are made. At threshold, the experimental dissociation rate is almost 10{sup 3} faster than RRKM predictions. Reasons for this apparent non-RRKM behavior will be discussed.

Clarkson, Jasper R.; Herbert, John M.; Zwier, Timothy S. [Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Chemistry, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States)

2007-04-07

257

Structure and dynamics of excited atoms. Final report, 15 November 1989-14 November 1994  

SciTech Connect

During the five year period of grant AFOSR-9O-0036 the authors have worked on two different kinds of projects, microwave multiphoton processes and resonant collisional energy transfer. Both kinds of experiments are carried out with highly excited, or Rydberg atoms, which allow the authors to do quantitative experiments giving insights which would be difficult or impossible to obtain in other systems. For example, the experiments on microwave multiphoton excitation and ionization have demonstrated that the Floquet, or dressed state, approach provides an accurate description of the evolution of atomic systems in intense radiation pulses. The understanding derived from these microwave experiments resolved a controversy about how laser multiphoton ionization through intermediate resonances occurred. In the two following sections of this report the authors describe the collision experiments and the microwave multiphoton experiments.

Gallagher, T.

1995-03-01

258

Achieving molecular selectivity in imaging using multiphoton Raman spectroscopy techniques  

SciTech Connect

In the case of most imaging methods, contrast is generated either by physical properties of the sample (Differential Image Contrast, Phase Contrast), or by fluorescent labels that are localized to a particular protein or organelle. Standard Raman and infrared methods for obtaining images are based upon the intrinsic vibrational properties of molecules, and thus obviate the need for attached flurophores. Unfortunately, they have significant limitations for live-cell imaging. However, an active Raman method, called Coherent Anti-Stokes Raman Scattering (CARS), is well suited for microscopy, and provides a new means for imaging specific molecules. Vibrational imaging techniques, such as CARS, avoid problems associated with photobleaching and photo-induced toxicity often associated with the use of fluorescent labels with live cells. Because the laser configuration needed to implement CARS technology is similar to that used in other multiphoton microscopy methods, such as two -photon fluorescence and harmonic generation, it is possible to combine imaging modalities, thus generating simultaneous CARS and fluorescence images. A particularly powerful aspect of CARS microscopy is its ability to selectively image deuterated compounds, thus allowing the visualization of molecules, such as lipids, that are chemically indistinguishable from the native species.

Holtom, Gary R. (BATTELLE (PACIFIC NW LAB)); Thrall, Brian D. (BATTELLE (PACIFIC NW LAB)); Chin, Beek Yoke (BATTELLE (PACIFIC NW LAB)); Wiley, H Steven (BATTELLE (PACIFIC NW LAB)); Colson, Steven D. (BATTELLE (PACIFIC NW LAB))

2000-12-01

259

Near infrared and visible luminescence from xerogels covalently grafted with lanthanide [Sm(3+), Yb(3+), Nd(3+), Er(3+), Pr(3+), Ho(3+)] ?-diketonate derivatives using visible light excitation.  

PubMed

A series of ternary lanthanide ?-diketonate derivatives covalently bonded to xerogels (named as Ln-DP-xerogel, Ln = Sm, Yb, Nd, Er, Pr, Ho) by doubly functionalized alkoxysilane (dbm-Si) was synthesized in situ via a sol-gel process. The properties of these xerogel materials were investigated by Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and fluorescence spectroscopy. The data and analyses suggest that the lanthanide derivatives have been covalently grafted to the corresponding xerogels successfully. Of importance here is that, after excitation with visible light (400-410 nm), the xerogels all show characteristic visible (Sm(3+)) as well as near-infrared (NIR; Sm(3+), Yb(3+), Nd(3+), Er(3+), Pr(3+), Ho(3+)) luminescence of the corresponding Ln(3+) ions, which is attributed to the energy transfer from the ligands to the Ln(3+) ions via an antenna effect. Exciting with visible light is advantageous over UV excitation. Furthermore, to the best of our knowledge, it is the first observation of NIR luminescence with visible light excitation from xerogels covalently bonded with the Sm(3+), Pr(3+), and Ho(3+) derivatives. Compared to lanthanide complexes (Ln = Er, Nd, Yb) functionalized periodic mesoporous organosilica (PMO) materials that exhibit similar optical properties reported in our previous work, the Ln-DP-xerogel (Ln = Sm, Yb, Nd, Er, Pr, Ho) in this case offer advantages in terms of ease of synthesis and handling and potentially low cost for emerging technological applications. Development of near-infrared luminescence of the lanthanide materials with visible light excitation is of strong interest to emerging applications such as chemosensors, laser systems, and optical amplifiers. PMID:24063535

Sun, Lining; Qiu, Yannan; Liu, Tao; Zhang, Jin Z; Dang, Song; Feng, Jing; Wang, Zhijuan; Zhang, Hongjie; Shi, Liyi

2013-10-01

260

The multiphoton ionization of uranium hexafluoride. Revision 1  

SciTech Connect

Multiphoton ionization (MPI) time-of-flight mass spectroscopy and photoelectron spectroscopy studies of UF{sub 6} have been conducted using focused light from the Nd:YAG laser fundamental ({lambda}=1064 nm) and its harmonics ({lambda}=532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UF{sub x}{sup +} fragment ions even at the lowest laser power densities at which signal could be detected. The laser power dependence of U{sup n+} ions signals indicates that saturation can occur for many of the steps required for their ionization. In general, the doubly-charged uranium ion (U{sup 2+}) intensity is much greater than that of the singly-charged uranium ion (U{sup +}). For the case of the tunable dye laser experiments, the U{sup n+} (n = 1- 4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The dominance of the U{sup 2+} ion and the absence or very small intensities of UF{sub x}{sup +} fragments, along with the unsaturated wavelength dependence, indicate that mechanisms may exist other than ionization of bare U atoms after the stepwise photodissociation of F atoms from the parent molecule.

Armstrong, D.P. [Oak Ridge K-25 Site, TN (United States). UEO Enrichment Technical Operations Div.] [Oak Ridge K-25 Site, TN (United States). UEO Enrichment Technical Operations Div.

1992-05-01

261

Physical and biological limitations of in vivo multiphoton fluorescence microscopy  

NASA Astrophysics Data System (ADS)

In this paper we present experimental and theoretical study of limitations on deep imaging of biological tissue structure using multiphoton fluorescence microscopy (MFM), that are imposed by scattering of short NIR pulses in optically turbid medium. The time stretching of the laser pulse and its transversal widening limit the maximum imaging depth of MFM since the magnitude of fluorescence response from the medium is the power function of energy flux density in the excitation laser beam. Increasing the imaging depth by raising the laser power may result in phototoxic damage of biological objects. We have theoretically and experimentally studied temporal structure of collimated femtosecond laser pulse scattered in an optically turbid model medium with controlled concentration of micron-sized spherical beads. In parallel we investigated phototoxic effect on biological liquid at high-intense femtosecond NIR pulse irradiation for various expositions by structural analysis of dehydrated blood plasma droplet. The irradiation regimes were found with complete recovery of the droplet structure, as well as with its slight and severe stable modification.

Korytin, Alexey I.; Sergeeva, Ekaterina A.; Shcherbatyuk, Tatiana; Parfenova, Irina

2005-03-01

262

Spectroscopic analysis of skin intrinsic signals for multiphoton microscopy  

NASA Astrophysics Data System (ADS)

We recorded multiphoton images of human skin biopsies using endogenous sources of nonlinear optical signals. We detected simultaneously two-photon excited fluorescence (2PEF) from intrinsic fluorophores and second harmonic generation (SHG) from collagen. We observed SHG from fibrillar collagens in the dermis, whereas no SHG was detectable from the non fibrillar type IV collagen in the basal laminae. We compared these distinct behaviours of collagens I and IV in SHG microscopy to polarization-resolved surface SHG experiments on thin films of collagens I and IV molecules. We observed similar signals for both types of molecular films, except for the chiroptical contributions which are present only for collagen I and enhance the signal typically by a factor of 2. We concluded that SHG microscopy is a sensitive probe of the micrometer-scale structural organization of collagen in biological tissues. In order to elucidate the origin of the endogenous fluorescence signals, we recorded 2PEF spectra at various positions in the skin biopsies, and compared these data to in vitro spectroscopic analysis. In particular, we studied the keratin fluorescence and determined its 2PEF action cross section. We observed a good agreement between 2PEF spectra recorded in the keratinized upper layers of the epidermis and in a solution of purified keratin. Finally, to illustrate the capabilities of this technique, we recorded 2PEF/SHG images of skin biopsies obtained from patients of various ages.

Pena, Ana-Maria; Strupler, Mathias; Boulesteix, Thierry; Senni, Karim; Godeau, Gaston; Beaurepaire, Emmanuel; Schanne-Klein, Marie-Claire

2006-02-01

263

Increased time resolution with multiphoton interference beating  

NASA Astrophysics Data System (ADS)

I investigate a variation of Hong-Ou-Mandel interference where two interference filters with different central frequencies are placed in the two output-ports of a beam splitter. Taking photons as wavepackets in the time domain, we get a general analytic formula for the probability that N photons emerge in each output-port after interference. The probability is shown to oscillate as a cosine function modulated by a dip and the oscillation period is inversely proportional to N which indicates a better time resolution with multiphoton beating.

Chen, Lei

2014-11-01

264

Monodispersed LaF3 nanocrystals: shape-controllable synthesis, excitation-power-dependent multi-color tuning and intense near-infrared upconversion emission  

NASA Astrophysics Data System (ADS)

In this study, monodispersed and high-quality hexagonal phase LaF3 nanocrystals with different shapes and sizes were synthesized by a solvothermal method using oleic acid as the stabilizing agent. The as-prepared LaF3 nanocrystals were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD), and analysis of the upconversion spectra. The TEM results reveal that the samples present high uniformity and monodispersity and are self-assembled into a two-dimensional ordered array. Moreover, the shape, size and structure of the nanocrystals can be readily tuned by adjusting the NaF content. With increasing content of NaF, the shape of the LaF3 nanocrystals changed from particle to rod and the size gradually increased. More importantly, high NaF content favors the formation of one-dimensional nanorods. High Y b3+ and Er3+ content is beneficial to synthesizing the hexagonal phase of NaLaF4 nanocrystals. Furthermore, the TEM results show that the shape and size of the LaF3 nanocrystals can also be tuned by doping lanthanide ions, which provides a new route for size and shape control of nanocrystals. In addition, LaF3 nanocrystals co-doped with Y b3+/Tm3+ present efficient near-infrared (NIR)-NIR upconversion luminescence. More importantly, the upconversion luminescent colors can be readily tuned from blue-white to blue by adjusting the excitation power. Therefore, it is expected that these LaF3 nanocrystals with well-controlled shape, size and NIR-NIR upconversion emission have potential applications in biomedical imaging fields.

Rao, Ling; Lu, Wei; Ren, Guozhong; Wang, Haibo; Yi, Zhigao; Liu, Hongrong; Zeng, Songjun

2014-02-01

265

Excitation of the low lying vibrational levels of H2O by O(3P) as measured on Spacelab 2  

NASA Technical Reports Server (NTRS)

The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(3P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (101) level at an O(3P) velocity of approximately 7.75 km/s. Contributions to the radiation in the 1.7-3.0 micron band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 micron and the nighttime data for the 1.7-3.0 micron sensors are consistent with being explained by collision excitation of H2O by O(3P), (2) diurnal variations of 4.5-9.5 micron intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests greater than 60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 micron intensity data suggests that O(+) may likely be instrumental in producing excited H2O(+) through charge exchange.

Meyerott, R. E.; Swenson, G. R.; Schweitzer, E. L.; Koch, D. G.

1994-01-01

266

Excitation of the low lying vibrational levels of H2O by O(3P) as measured on Spacelab 2  

NASA Astrophysics Data System (ADS)

The data from the infrared telescope (IRT), which was flown on space shuttle Challenger Spacelab 2 mission (July 1985), were originally reported by Koch et al. (1987) as originating from near orbital emissions, primarily H2O. In this study, analysis of this data was extended to determine the collisional cross sections for the excitation of the low lying vibrational levels of H2O, present in the orbiter cloud, by atmospheric O(3P). The evaluation of the contribution to the measured signal from solar excitation and ram O excitation of outgassing H2O permits the determination of the H2O column density and the excitation cross section of the (101) level at an O(3P) velocity of approximately 7.75 km/s. Contributions to the radiation in the 1.7-3.0 micron band by transitions from the (100), (001), and multiquantum excited levels are discussed. The findings of the study are (1) the IRT data for the 4.5-9.5 micron and the nighttime data for the 1.7-3.0 micron sensors are consistent with being explained by collision excitation of H2O by O(3P), (2) diurnal variations of 4.5-9.5 micron intensities follow the model predicted O density for a full orbit, (3) daytime increases in the H2O cloud density were not evident, (4) the cross sections for the collisional excitation process are derived and compared to values computated by Johnson (1986) and Redmon et al. (1986), (5) theoretical investigation suggests greater than 60% of the radiation from H2O is a result of multiphoton emission resulting from collisional multiquanta excitation, and (6) the large daytime increase in the 1.7-3.0 micron intensity data suggests that O(+) may likely be instrumental in producing excited H2O(+) through charge exchange.

Meyerott, R. E.; Swenson, G. R.; Schweitzer, E. L.; Koch, D. G.

1994-09-01

267

Multiphoton microscopy using intrinsic signals for pharmacological studies in unstained cardiac and vascular tissue  

NASA Astrophysics Data System (ADS)

We report two novel applications of multiphoton microscopy for pharmacological studies of unstained cardiovascular tissue. First, we show that second harmonic generation (SHG) microscopy of unstained cardiac myocytes can be used to determine the sarcomere length with sub-resolution accuracy, owing to the remarkable contrast of the SHG signal originating from myosin filaments. A measurement precision of 20 nm is achieved, taking the sample variability into account. We used this technique to measure sarcomere contracture in the presence of saxitoxin, and results were in agreement with mechanical measurements of atrial tissue contracture. Second, we characterized multiphoton microscopy of intact unlabeled arteries. We performed simultaneous detection of two-photon-excited fluorescence (2PEF) from elastin laminae and SHG from collagen fibers upon 860 nm excitation. Combined 2PEF/SHG images provide a highly specific, micron scale description of the architecture of these two major components of the vessel wall. We used this methodology to study the effects of lindane (a pesticide) on the artery wall structure and evidenced structural alteration of the vessel morphology.

Beaurepaire, Emmanuel; Boulesteix, Thierry; Pena, Ana-Maria; Pages, Nicole; Senni, Karim; Godeau, Gaston; Sauviat, Martin-Pierre; Schanne-Klein, Marie-Claire

2005-03-01

268

Multi-photon states and their measurement  

NASA Astrophysics Data System (ADS)

Generation of multi-photon states (such as for instance three- and four-photon states) is one of the most challenging problems of modern quantum optics. In many works the authors claim to have produced such states by means of overlapping photon pairs generated in spontaneous parametric down-conversion (SPDC). Moreover three- and four-photon states generated this way have been used for observing Greenberger-Horne-Zeilinger (GHZ) polarization states testing Bell's inequalities for spin-1 quantum systems preparing W-states and other applications. In this paper we show that the criterion for obtaining three- or four-photon states is the behavior of the corresponding normalized Glauber's correlation function. Calculations carried out for the case of SPDC or even PDC in the stimulated regime demonstrate that these processes are not capable of generating three- or four-photon states: photon statistics reveals typically two-photon behaviour. We suggest a method of measuring higher-order correlation functions in the pulsed regime which allows one to study multi-photon correlations for these and many other processes.

Iskhakov, T. S.; Ivanova, O. A.; Chekhova, Maria V.

2005-06-01

269

Multiphoton ionization of large water clusters  

SciTech Connect

Water clusters are multimers of water molecules held together by hydrogen bonds. In the present work, multiphoton ionization in the UV range coupled with time of flight mass spectrometry has been applied to water clusters with up to 160 molecules in order to obtain information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. The dependence of ion intensities of water clusters and their metastable fragments produced by laser ionization at 355 nm on laser power density indicates a (3+1)-photon resonance-enhanced multiphoton ionization process. It also explains the large increase of ionization efficiency at 355 nm compared to that at 266 nm. Indeed, it was found, by applying both nanosecond and picosecond laser ionization with the two different UV wavelengths, that no water cluster sequences after n = 9 could be observed at 266 nm, whereas water clusters up to m/z 2000 Th in reflectron mode and m/z 3000 Th in linear mode were detected at 355 nm. The agreement between our findings on clusters of water, especially true in the range with n > 10, and reported data for liquid water supports the hypothesis that clusters above a critical dimension can approximate the liquid phase. It should thus be possible to study clusters just above 10 water molecules, for getting information on the bulk phase structure.

Apicella, B., E-mail: apicella@irc.cnr.it [Combustion Research Institute, IRC–C.N.R., P.le Tecchio 80, 80125 Napoli (Italy); Li, X. [Key Laboratory of Power Machinery and Engineering, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240 (China); Passaro, M. [CNISM and Chemical Engineering, Materials and Industrial Production Department, University of Naples “Federico II,” P.le Tecchio 80, 80125 Napoli (Italy); Spinelli, N. [CNISM and Physics Department, University of Naples “Federico II,” Via Cintia, 80124 Napoli (Italy); Wang, X. [SPIN–C.N.R., Via Cintia, 80124 Napoli (Italy)

2014-05-28

270

High Resolution Multiphoton Spectroscopy by a Tunable Free-Electron-Laser Light  

NASA Astrophysics Data System (ADS)

Seeded free electron lasers theoretically have the intensity, tunability, and resolution required for multiphoton spectroscopy of atomic and molecular species. Using the seeded free electron laser FERMI and a novel detection scheme, we have revealed the two-photon excitation spectra of dipole-forbidden doubly excited states in helium. The spectral profiles of the lowest (-1 ,0 )+1 Se 1 and (0 ,1 )0 De 1 resonances display energy shifts in the meV range that depend on the pulse intensity. The results are explained by an effective two-level model based on calculated Rabi frequencies and decay rates.

Žitnik, M.; Miheli?, A.; Bu?ar, K.; Kav?i?, M.; Rubensson, J.-E.; Svanquist, M.; Söderström, J.; Feifel, R.; Sâthe, C.; Ovcharenko, Y.; Lyamayev, V.; Mazza, T.; Meyer, M.; Simon, M.; Journel, L.; Lüning, J.; Plekan, O.; Coreno, M.; Devetta, M.; Di Fraia, M.; Finetti, P.; Richter, R.; Grazioli, C.; Prince, K. C.; Callegari, C.

2014-11-01

271

Multiphoton microscopy system with a compact fiber-based femtosecond-pulse laser and handheld probe.  

PubMed

We report on the development of a compact multiphoton microscopy (MPM) system that integrates a compact and robust fiber laser with a miniature probe. The all normal dispersion fiber femtosecond laser has a central wavelength of 1.06 ?m, pulse width of 125 fs and average power of more than 1 W. A double cladding photonic crystal fiber was used to deliver the excitation beam and to collect the two-photon signal. The hand-held probe included galvanometer-based mirror scanners, relay lenses and a focusing lens. The packaged probe had a diameter of 16 mm. Second harmonic generation (SHG) images and two-photon excited fluorescence (TPEF) images of biological tissues were demonstrated using the system. PMID:20635426

Liu, Gangjun; Kieu, Khanh; Wise, Frank W; Chen, Zhongping

2011-01-01

272

Generation of extended light-sheets for single and multi-photon fluorescence microscopy  

NASA Astrophysics Data System (ADS)

We theoretically propose and computationally demonstrate the generation of extended light-sheet for fluorescence microscopy. This is made possible by the introduction of a specially designed double-window spatial filter that allows the light to pass through the periphery and center of a cylindrical lens. When illuminated with a plane wave, the proposed filter results in an extended depth-of-focus along with side-lobes which are due to other interferences in the transverse focal plane. Computational studies show a maximum extension of light-sheet by 3.38 times for single photon excitation and 3.68 times for multiphoton excitation as compared to state-of-art single plane illumination microscopy system. This technique may facilitate the study of large biological specimens (such as Zebrafish embryo and tissue) with high spatial resolution and reduced photobleaching.

Purnapatra, Subhajit B.; Pratim Mondal, Partha

2013-07-01

273

Multiphoton imaging of biological samples during freezing and heating  

NASA Astrophysics Data System (ADS)

We applied multiphoton microscopic imaging to observe freezing and heating effects in plant- and animal cell samples. The experimental setups consisted of a multiphoton imaging system and a heating and cooling stage which allows for precise temperature control from liquid nitrogen temperature (-196°C 77 K) up to +600°C (873 K) with heating/freezing rates between 0.01 K/min and 150 K/min. Two multiphoton imaging systems were used: a system based on a modified optical microscope and a flexible mobile system. To illustrate the imaging capabilities, plant leafs as well as animal cells were microscopically imaged in vivo during freezing based on autofluorescence lifetime and intensity of intrinsic molecules. The measurements illustrate the usefulness of multiphoton imaging to investigate freezing effects on animal and plant cells.

Breunig, H. G.; Uchugonova, A.; König, K.

2014-02-01

274

Differentiation of normal and cancerous lung tissues by multiphoton imaging  

E-print Network

We utilize multiphoton microscopy for the label-free diagnosis of noncancerous, lung adenocarcinoma (LAC), and lung squamous cell carcinoma (SCC) tissues from humans. Our results show that the combination of second-harmonic ...

Wang, Chun-Chin

275

Multiphoton path entanglement by non-local bunching  

E-print Network

Multiphoton path entanglement is created without applying post-selection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the non-local bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2006-01-03

276

Intravital multiphoton microscopy for imaging hepatobiliary function  

NASA Astrophysics Data System (ADS)

Liver is the chemical factory in body responsible for important functions such as metabolism and detoxification. When liver can not be regenerated in time to amend damages that has occurred, failure of hepatic functions can result. Traditionally, the study of liver pathology has depended on histological techniques, but such methods are limited to ex-vivo observation. In order to study hepatic metabolism in vivo, we have designed a hepatic imaging chamber made of biocompatible titanium alloy (6V4Al-Ti, ELI grade). In combination with multiphoton and second harmonic generation microscopy, our approach allows the intravital observation of hepatic intravital activities to be achieved. Processes such as hepatic metabolism and disease progression can be studied using this methodology.

Li, Feng-Chieh; Sun, Tzu-Lin; Lee, Hsuan-Shu; Yang, Shu-Mei; Dong, Chen-Yuan

2007-07-01

277

Complex-scaling generalized pseudospectral method for quasienergy resonance states in two-center systems: Application to the Floquet study of charge resonance enhanced multiphoton ionization of molecular ions in intense low-frequency laser fields  

E-print Network

to the effect of charge-resonance-enhanced multiphoton resonances of the 1?g and 1?u states with excited electronic states at some particular internuclear distances. These “critical” distances depend on the details of molecular electronic structure and the laser...

Chu, Shih-I; Chu, Xi

2000-12-13

278

Multiphoton Dissociation of Electrosprayed MegaDalton-Sized DNA Ions in a Charge-Detection Mass Spectrometer  

NASA Astrophysics Data System (ADS)

Charge detection mass spectrometry in combination with a linear electrostatic ion trap coupled to a continuous wavelength infrared CO2 laser has been used to study the multiphoton dissociation of DNA macromolecular ions. Samples, with masses ranging from 2.23 to 31.5 MDa, include single strand circular M13mp18, double strand circular M13mp18, and double strand linear LambdaPhage DNA fragments. Their activation energies for unimolecular dissociation were determined. Activation energy values slightly increase as a function of the molecular weight. The most important result is the difference between the fragmentations observed for hybridized double-strands and dimers of single strands.

Doussineau, Tristan; Paletto, Pierre; Dugourd, Philippe; Antoine, Rodolphe

2015-01-01

279

Multiphoton Dissociation of Electrosprayed MegaDalton-Sized DNA Ions in a Charge-Detection Mass Spectrometer.  

PubMed

Charge detection mass spectrometry in combination with a linear electrostatic ion trap coupled to a continuous wavelength infrared CO2 laser has been used to study the multiphoton dissociation of DNA macromolecular ions. Samples, with masses ranging from 2.23 to 31.5 MDa, include single strand circular M13mp18, double strand circular M13mp18, and double strand linear LambdaPhage DNA fragments. Their activation energies for unimolecular dissociation were determined. Activation energy values slightly increase as a function of the molecular weight. The most important result is the difference between the fragmentations observed for hybridized double-strands and dimers of single strands. PMID:25348472

Doussineau, Tristan; Paletto, Pierre; Dugourd, Philippe; Antoine, Rodolphe

2015-01-01

280

Single-wavelength reflected confocal and multiphoton microscopy for tissue imaging  

NASA Astrophysics Data System (ADS)

Both reflected confocal and multiphoton microscopy can have clinical diagnostic applications. The successful combination of both modalities in tissue imaging enables unique image contrast to be achieved, especially if a single laser excitation wavelength is used. We apply this approach for skin and corneal imaging using the 780-nm output of a femtosecond, titanium-sapphire laser. We find that the near-IR, reflected confocal (RC) signal is useful in characterizing refractive index varying boundaries in bovine cornea and porcine skin, while the multiphoton autofluorescence (MAF) and second-harmonic generation (SHG) intensities can be used to image cytoplasm and connective tissues (collagen), respectively. In addition, quantitative analysis shows that we are able to detect MAF from greater imaging depths than with the near-IR RC signal. Furthermore, by performing RC imaging at 488, 543, and 633 nm, we find that a longer wavelength leads to better image contrast for deeper imaging of the bovine cornea and porcine skin tissue. Finally, by varying power of the 780-nm source, we find that comparable RC image quality was achieved in the 2.7 to 10.7-mW range.

Chen, Wei-Liang; Chou, Chen-Kuan; Lin, Ming-Gu; Chen, Yang-Fang; Jee, Shiou-Hwa; Tan, Hsin-Yuan; Tsai, Tsung-Hua; Kim, Ki-Hean; Kim, Daekeun; So, Peter T. C.; Lin, Sung-Jan; Dong, Chen-Yuan

2009-09-01

281

Spectrally Resolved Multiphoton Imaging of In Vivo and Excised Mouse Skin Tissues  

PubMed Central

The deep tissue penetration and submicron spatial resolution of multiphoton microscopy and the high detection efficiency and nanometer spectral resolution of a spectrograph were utilized to record spectral images of the intrinsic emission of mouse skin tissues. Autofluorescence from both cellular and extracellular structures, second-harmonic signal from collagen, and a narrowband emission related to Raman scattering of collagen were detected. Visualization of the spectral images by wavelength-to-RGB color image conversion allowed us to identify and discriminate tissue structures such as epidermal keratinocytes, lipid-rich corneocytes, intercellular structures, hair follicles, collagen, elastin, and dermal cells. Our results also showed morphological and spectral differences between excised tissue section, thick excised tissue, and in vivo tissue samples of mouse skin. Results on collagen excitation at different wavelengths suggested that the origin of the narrowband emission was collagen Raman peaks. Moreover, the oscillating spectral dependency of the collagen second-harmonic intensity was experimentally studied. Overall, spectral imaging provided a wealth of information not easily obtainable with present conventional multiphoton imaging systems. PMID:17449667

Palero, Jonathan A.; de Bruijn, Henriëtte S.; van der Ploeg van den Heuvel, Angélique; Sterenborg, Henricus J. C. M.; Gerritsen, Hans C.

2007-01-01

282

Time- and spectral-resolved multiphoton imaging of fresh bladder biopsies  

NASA Astrophysics Data System (ADS)

Human tissues intrinsically contains many fluorophores, as such NADH, elastin, collagen, and flavins, that can be excited and imaged using multiphoton microscopy, up to 150 microns depth. In this work we used combined two photon intrinsic fluorescence (TPE), second harmonic generation microscopy (SHG), fluorescence lifetime imaging microscopy (FLIM), and multispectral two photon emission detection (MTPE) to investigate different kinds of human ex-vivo fresh biopsies of bladder. Morphological and spectroscopic analyses allowed to characterize both healthy and pathological tissue samples in a good agreement with common routine histology. In particular, we examined tissue samples from bladder normal mucosa, and bladder carcinoma in-situ (CIS), finding both morphological and spectroscopic differences. From the morphological point of view, cancer cells appeared more elongated with respect to corresponding normal cells; they also exhibited a different nucleus to cytoplasm ratio. From the spectroscopic point of view, we found differences between the two tissue types in both spectral emission and fluorescence lifetime distribution. Even if further analysis, as well as a more significant statistics on a large number of samples would be helpful to discriminate between low and high grade cancer, our method is a promising tool to be used as diagnostic confirmation of histological results, as well as a diagnostic tool in a multiphoton endoscope or cystoscope to be used in in-vivo imaging applications.

Cicchi, Riccardo; Crisci, Alfonso; Nesi, Gabriella; Cosci, Alessandro; Giancane, Saverio; Carini, Marco; Pavone, Francesco S.

2009-07-01

283

Label-free monitoring of colorectal adenoma–carcinoma sequence based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

The monitoring and evaluation of colorectal adenoma–carcinoma sequence during endoscopy are important for endoscopic resection of precursor lesions to disrupt the adenoma–carcinoma sequence and halt progression to invasive neoplastic disease. In this study, multiphoton microscopy (MPM) was used to identify different stages during the development of colorectal adenocarcinoma including adenoma with low-grade and high-grade dysplasia, and adenocarcinoma invading the submucosa. It was found that by combining two-photon excited fluorescence (TPEF) imaging and second harmonic generation (SHG) imaging, MPM can reveal the morphological changes of the epithelial cells and glands, identify the invasive position and depth of atypical glands and quantitatively describe the change of the cellular nucleus and the nuclear-to-cytoplasmic ratio during the stepwise progression of colorectal adenocarcinoma. These are important pathological findings for pathologists when diagnosing colorectal lesions. With the advancement of a compact and flexible multiphoton endoscope for in vivo imaging and clinical applications, MPM has the potential to provide immediate histological diagnosis for the monitoring and evaluation of the colorectal adenoma–carcinoma sequence during endoscopy.

Chen, J. X.; Li, H. S.; Chen, Z. F.; Feng, C. Y.; Yang, Y. H.; Jiang, W. Z.; Guan, G. X.; Zhu, X. Q.; Zhuo, S. M.; Xu, J.

2014-06-01

284

Multiphoton microscopic imaging of fibrotic focus in invasive ductal carcinoma of the breast  

NASA Astrophysics Data System (ADS)

During the proliferation of breast cancer, the desmoplastic can evoke a fibrosis response by invading healthy tissue. Fibrotic focus (FF) in invasive ductal carcinoma (IDC) of the breast had been reported to be associated with significantly poorer survival rate than IDC without FF. As an important prognosis indicator, it's difficult to obtain the exact fibrotic information from traditional detection method such as mammography. Multiphoton imaging based on two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) has been recently employed for microscopic examination of unstained tissue. In this study, multiphoton microscopy (MPM) was used to image the fibrotic focus in invasive ductal carcinoma tissue. The morphology and distribution of collagen in fibrotic focus can be demonstrated by the SHG signal. Variation of collagen between IDC with and without FF will be examined and further characterized, which may be greatly related to the metastasis of breast cancer. Our result suggested that the MPM can be efficient in identifying and locating the fibrotic focus in IDC. Combining with the pathology analysis and other detecting methods, MPM owns potential in becoming an advanced histological tool for detecting the fibrotic focus in IDC and collecting prognosis information, which may guide the subsequent surgery option and therapy procedure for patients.

Chen, Sijia; Nie, Yuting; Lian, Yuane; Wu, Yan; Fu, Fangmeng; Wang, Chuan; Zhuo, Shuangmu; Chen, Jianxin

2014-11-01

285

Setup and use of a two-laser multiphoton microscope for multichannel intravital fluorescence imaging  

PubMed Central

Characterizing biological mechanisms dependent upon the interaction of many cell types in vivo requires both multiphoton microscope systems capable of expanding the number and types of fluorophores that can be imaged simultaneously while removing the wavelength and tunability restrictions of existing systems, and enhanced software for extracting critical cellular parameters from voluminous 4D data sets. We present a procedure for constructing a two-laser multiphoton microscope that extends the wavelength range of excitation light, expands the number of simultaneously usable fluorophores and markedly increases signal to noise via ‘over-clocking’ of detection. We also utilize a custom-written software plug-in that simplifies the quantitative tracking and analysis of 4D intravital image data. We begin by describing the optics, hardware, electronics and software required, and finally the use of the plug-in for analysis. We demonstrate the use of the setup and plug-in by presenting data collected via intravital imaging of a mouse model of breast cancer. The procedure may be completed in ~24 h. PMID:21959234

Entenberg, David; Wyckoff, Jeffrey; Gligorijevic, Bojana; Roussos, Evanthia T; Verkhusha, Vladislav V; Pollard, Jeffrey W; Condeelis, John

2014-01-01

286

Label-free imaging characteristics of colonic mucinous adenocarcinoma using multiphoton microscopy.  

PubMed

Colorectal carcinoma (CRC) has high mortality and increased incidence rates. An early detection of CRC is very important. Multiphoton microscopy (MPM) with high resolution and high sensitivity is used to effectively distinguish the microstructure changes of normal and mucinous adenocarcinoma slices of ex vivo human colonic tissues. In mucinous adenocarcinoma mucosa, the glands are distorted and elongated, the gland cavity is indistinct, and the mesh collagen fibers are diminished. In the submucosa, the collagens are seriously disordered, elongated, pushed aside, and sparsely visible, the content of elastic fibers is also broken and almost disappearing. Many cancer cells, some in cavity-like shape full of mucus surrounded by some collagen fibers, occupied the submucosa, which are comparable to hematoxylin-eosin (HE) stained images. Second harmonic generation and two-photon excitation fluorescence (SHG/TPEF) intensity ratio can be used further to quantitatively evaluate normality and abnormality. The fast Fourier transform (FFT) images show that the normal collagen fibrils are dense and in random order, and the cancerous collagen is certainly organized. The exploratory results show that it has potential for the development of multiphoton mini-endoscopy in real-time early diagnosis of CRC. PMID:23168617

Liu, Nenrong; Chen, Jianxin; Xu, Renan; Jiang, Shanghai; Xu, Jian; Chen, Rong

2013-01-01

287

In Vivo Multiphoton NADH Fluorescence Reveals Depth-Dependent Keratinocyte Metabolism in Human Skin  

PubMed Central

We employ a clinical multiphoton microscope to monitor in vivo and noninvasively the changes in reduced nicotinamide adenine dinucleotide (NADH) fluorescence of human epidermal cells during arterial occlusion. We correlate these results with measurements of tissue oxy- and deoxyhemoglobin concentration during oxygen deprivation using spatial frequency domain imaging. During arterial occlusion, a decrease in oxyhemoglobin corresponds to an increase in NADH fluorescence in the basal epidermal cells, implying a reduction in basal cell oxidative phosphorylation. The ischemia-induced oxygen deprivation is associated with a strong increase in NADH fluorescence of keratinocytes in layers close to the stratum basale, whereas keratinocytes from epidermal layers closer to the skin surface are not affected. Spatial frequency domain imaging optical property measurements, combined with a multilayer Monte Carlo-based radiative transport model of multiphoton microscopy signal collection in skin, establish that localized tissue optical property changes during occlusion do not impact the observed NADH signal increase. This outcome supports the hypothesis that the vascular contribution to the basal layer oxygen supply is significant and these cells engage in oxidative metabolism. Keratinocytes in the more superficial stratum granulosum are either supplied by atmospheric oxygen or are functionally anaerobic. Based on combined hemodynamic and two-photon excited fluorescence data, the oxygen consumption rate in the stratum basale is estimated to be ?0.035 ?moles/106 cells/h. PMID:23332078

Balu, Mihaela; Mazhar, Amaan; Hayakawa, Carole K.; Mittal, Richa; Krasieva, Tatiana B.; König, Karsten; Venugopalan, Vasan; Tromberg, Bruce J.

2013-01-01

288

Optical workstation with concurrent, independent multiphoton imaging and experimental laser microbeam capabilities  

PubMed Central

Experimental laser microbeam techniques have become established tools for studying living specimens. A steerable, focused laser beam may be used for a variety of experimental manipulations such as laser microsurgery, optical trapping, localized photolysis of caged bioactive probes, and patterned photobleaching. Typically, purpose-designed experimental systems have been constructed for each of these applications. In order to assess the consequences of such experimental optical interventions, long-term, microscopic observation of the specimen is often required. Multiphoton excitation, because of its ability to obtain high-contrast images from deep within a specimen with minimal phototoxic effects, is a preferred technique for in vivo imaging. An optical workstation is described that combines the functionality of an experimental optical microbeam apparatus with a sensitive multiphoton imaging system designed for use with living specimens. Design considerations are discussed and examples of ongoing biological applications are presented. The integrated optical workstation concept offers advantages in terms of flexibility and versatility relative to systems implemented with separate imaging and experimental components. PMID:18607511

Wokosin, David L.; Squirrell, Jayne M.; Eliceiri, Kevin W.; White, John G.

2008-01-01

289

Chronic imaging of amyloid plaques in the live mouse brain using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Transgenic mice expressing the human Amyloid Precursor Protein (APP) develop amyloid plaques as they age. These plaques resemble those found in the human disease. Multiphoton laser scanning microscopy combined with a novel surgical approach was used to measure amyloid plaque dynamics chronically in the cortex of living transgenic mice. Thioflavine S (thioS) was used as a fluorescent marker of amyloid deposits. Multiphoton excitation allowed visualization of amyloid plaques up to 200 micrometers deep into the brain. The surgical site could be imaged repeatedly without overt damage to the tissue, and individual plaques within this volume could be reliably identified over periods of several days to several months. On average, plaque sizes remained constant over time, supporting a model of rapid deposition, followed by relative stability. Alternative reporters for in vivo histology include thiazine red, and FITC-labeled amyloid-(Beta) peptide. We also present examples of multi-color imaging using Hoechst dyes and FITC-labeled tomato lectin. These approaches allow us to observe cell nuclei or microglia simultaneously with amyloid-(Beta) deposits in vivo. Chronic imaging of a variety of reporters in these transgenic mice should provide insight into the dynamics of amyloid-(Beta) activity in the brain.

Bacskai, Brian J.; Kajdasz, Stephen T.; Christie, R. H.; Zipfel, Warren R.; Williams, Rebecca M.; Kasischke, Karl A.; Webb, Watt W.; Hyman, B. T.

2001-04-01

290

Chaotic enhancement of hydrogen-atom excitation in magnetic and microwave fields Giuliano Benenti and Giulio Casati  

E-print Network

Chaotic enhancement of hydrogen-atom excitation in magnetic and microwave fields Giuliano Benenti 5 June 1997 We numerically investigate multiphoton ionization of excited hydrogen atoms in magnetic for the quantum localization length in the classically chaotic regime are in agreement with numerical data

Shepelyansky, Dima

291

Sub-15 fs multiphoton lithography of three-dimensional structures for live cell applications  

NASA Astrophysics Data System (ADS)

Development, morphology and intratissue location of cells are influenced by the 3D nano- and microenvironment. In this paper we demonstrate multiphoton photopolymerization to generate three-dimensional structures for cell culture applications with micro- and nanotopographic features using SU-8 photoresist and mr-NIL 6000 nanoimprint resist. Moving the focal spot of high-repetition rate near-infrared sub-15 fs pulsed laser light by a galvanometric beam scanner in combination with a piezoelectric vertical stage, nearly arbitrary trajectories of polymerized photoresist were generated. This technique can be used to generate cage structures with submicron interior features for live cell applications. Preliminary experiments with PC-3 and HT-1080 cells indicate the influence of the structures on cell behavior.

Licht, Martin; Uchugonova, Aisada; König, Karsten; Straub, Martin

2012-06-01

292

Multiphoton photoemission from a copper cathode illuminated by ultrashort laser pulses in an RF photoinjector.  

PubMed

In this Letter we report on the use of ultrashort infrared laser pulses to generate a copious amount of electrons by a copper cathode in an rf photoinjector. The charge yield verifies the generalized Fowler-Dubridge theory for multiphoton photoemission. The emission is verified to be prompt using a two pulse autocorrelation technique. The thermal emittance associated with the excess kinetic energy from the emission process is comparable with the one measured using frequency tripled uv laser pulses. In the high field of the rf gun, up to 50 pC of charge can be extracted from the cathode using a 80 fs long, 2 microJ, 800 nm pulse focused to a 140 mum rms spot size. Taking into account the efficiency of harmonic conversion, illuminating a cathode directly with ir laser pulses can be the most efficient way to employ the available laser power. PMID:20366937

Musumeci, P; Cultrera, L; Ferrario, M; Filippetto, D; Gatti, G; Gutierrez, M S; Moody, J T; Moore, N; Rosenzweig, J B; Scoby, C M; Travish, G; Vicario, C

2010-02-26

293

Theoretical Studies of Atomic and Molecular Multiphoton Processes in Intense and Superintense Laser Fields  

NASA Astrophysics Data System (ADS)

In this thesis work, several new nonperturbative theoretical formalisms and accurate and efficient computational methods are presented for ab initio comprehensive investigation of atomic and molecular multiphoton processes in intense and superintense laser fields. In the presence of strong fields, it is advantageous to treat the atoms/molecules quantum mechanically by using the time-dependent Schrodinger equation and treat the electromagnetic fields classically, leading to a set of coupled first-order time-dependent differential equations. The essence of the theoretical formalisms and computational methods developed can be summarized in the following several key elements: (1) For periodically or polychromatically time-dependent Hamiltonians, the time-dependent problems can be transformed into an equivalent time-independent infinite-dimensional Floquet Hamiltonians. (2) In the presence of external fields, all the bound states are coupled to the continuum and become quasi-bound states possessing complex quasi -energies. (3) To facilitate the calculation of the complex quasi-energies, a generalized pseudospectral technique is developed for the discretization of the non-Hermitian Floquet Hamiltonian and the construction of the Floquet matrix elements. (4) The Floquet matrices so generated are often very large scale, sparse, complex matrices. The formalisms and computational methods described above are applied to the studies of several high-intensity atomic and molecular multiphoton processes of current interests. The major accomplishments are summarized below: (1) The complex quasi-energies of excited states of atomic hydrogen in strong fields are determined for the first time. (2) Nonperturbative detailed calculations of the multiphoton detachment rates of H^- in one-color laser fields are performed for the first time. The intensity-averaged photodetachment rates calculated are in excellent agreement with those experimental data recently obtained in Los Alamos. (3) A generalized non-Hermitian two-mode Floquet theory is developed for the study of above-threshold multiphoton detachment of negative ions in intense two-color laser fields. (4) The two-color phase control of high-order harmonic generation (HHG) is investigated. It is shown that the HHG spectrum is sensitive to the relative phase of the two laser fields and a small admixture of a harmonic laser field to a fundamental laser field can lead to either increment or decrement of the HHG production rates. (5) The nature of chemical bond of D_2^+ molecules in intense one- and two-color laser fields is studied. An unexpected novel chemical bond hardening and molecular stabilization phenomenon is predicted: molecules initially prepared in highly excited vibrational states can become more stabilized and longer-lived with increasing laser intensity. Furthermore it is found that by tuning the relative phase between the fundamental and its third harmonic laser fields, the internuclear potential surface can be modified significantly, leading to a coherent control of the multiphoton dissociation dynamics. (Abstract shortened by UMI.).

Wang, Jingyan

294

Soliton dynamics in the multiphoton plasma regime  

PubMed Central

Solitary waves have consistently captured the imagination of scientists, ranging from fundamental breakthroughs in spectroscopy and metrology enabled by supercontinuum light, to gap solitons for dispersionless slow-light, and discrete spatial solitons in lattices, amongst others. Recent progress in strong-field atomic physics include impressive demonstrations of attosecond pulses and high-harmonic generation via photoionization of free-electrons in gases at extreme intensities of 1014 W/cm2. Here we report the first phase-resolved observations of femtosecond optical solitons in a semiconductor microchip, with multiphoton ionization at picojoule energies and 1010 W/cm2 intensities. The dramatic nonlinearity leads to picojoule observations of free-electron-induced blue-shift at 1016 cm?3 carrier densities and self-chirped femtosecond soliton acceleration. Furthermore, we evidence the time-gated dynamics of soliton splitting on-chip, and the suppression of soliton recurrence due to fast free-electron dynamics. These observations in the highly dispersive slow-light media reveal a rich set of physics governing ultralow-power nonlinear photon-plasma dynamics.

Husko, Chad A.; Combrié, Sylvain; Colman, Pierre; Zheng, Jiangjun; De Rossi, Alfredo; Wong, Chee Wei

2013-01-01

295

Results and prospects of laser separation of oxygen isotopes by IR multiphoton dissociation of molecules  

SciTech Connect

An experimental search was made for an initial oxygen compound suitable for laser separation of oxygen isotopes by IR multiphoton dissociation of molecules. Over ten molecules with C-O, Si-O, Cr=O, and C=O bonds were investigated. The excitation was provided by pulsed TEA CO{sub 2} laser radiation, and also by its second harmonic. Measurements were made of the dissociation yields of the molecular components containing {sup 18}O and {sup 16}O and of the isotopic selectivity as a function of the frequency and fluence of laser radiation, pressure of the gas being dissociated, etc. The suitability of the investigated compounds for practical laser separation of oxygen isotopes was analysed. 29 refs., 5 figs., 1 tab.

Laptev, V.B.; Ryabov, E.A.; Tumanova, L.M. [Inst. of Spectroscopy, Troitsk, Moscow Province (Russian Federation)] [Inst. of Spectroscopy, Troitsk, Moscow Province (Russian Federation)

1995-06-01

296

Three dimensional multiphoton imaging of fresh and whole mount developing mouse mammary glands  

PubMed Central

Background The applications of multiphoton microscopy for deep tissue imaging in basic and clinical research are ever increasing, supplementing confocal imaging of the surface layers of cells in tissue. However, imaging living tissue is made difficult by the light scattering properties of the tissue, and this is extraordinarily apparent in the mouse mammary gland which contains a stroma filled with fat cells surrounding the ductal epithelium. Whole mount mammary glands stained with Carmine Alum are easily archived for later reference and readily viewed using bright field microscopy to observe branching architecture of the ductal network. Here, we report on the advantages of multiphoton imaging of whole mount mammary glands. Chief among them is that optical sectioning of the terminal end bud (TEB) and ductal epithelium allows the appreciation of abnormalities in structure that are very difficult to ascertain using either bright field imaging of the stained gland or the conventional approach of hematoxylin and eosin staining of fixed and paraffin-embedded sections. A second advantage is the detail afforded by second harmonic generation (SHG) in which collagen fiber orientation and abundance can be observed. Methods GFP-mouse mammary glands were imaged live or after whole mount preparation using a Zeiss LSM510/META/NLO multiphoton microscope with the purpose of obtaining high resolution images with 3D content, and evaluating any structural alterations induced by whole mount preparation. We describe a simple means for using a commercial confocal/ multiphoton microscope equipped with a Ti-Sapphire laser to simultaneously image Carmine Alum fluorescence and collagen fiber networks by SHG with laser excitation set to 860 nm. Identical terminal end buds (TEBs) were compared before and after fixation, staining, and whole mount preparation and structure of collagen networks and TEB morphologies were determined. Flexibility in excitation and emission filters was explored using the META detector for spectral emission scanning. Backward scattered or reflected SHG (SHG-B) was detected using a conventional confocal detector with maximum aperture and forward scattered or transmitted SHG (SHG-F) detected using a non-descanned detector. Results We show here that the developing mammary gland is encased in a thin but dense layer of collagen fibers. Sparse collagen layers are also interspersed between stromal layers of fat cells surrounding TEBs. At the margins, TEBs approach the outer collagen layer but do not penetrate it. Abnormal mammary glands from an HAI-1 transgenic FVB mouse model were found to contain TEBs with abnormal pockets of cells forming extra lumens and zones of continuous lateral bud formation interspersed with sparse collagen fibers. Parameters influencing live imaging and imaging of fixed unstained and Carmine Alum stained whole mounts were evaluated. Artifacts induced by light scattering of GFP and Carmine Alum signals from epithelial cells were identified in live tissue as primarily due to fat cells and in whole mount tissue as due to dense Carmine Alum staining of epithelium. Carmine Alum autofluorescence was detected at excitation wavelengths from 750 to 950 nm with a peak of emission at 623 nm (~602-656 nm). Images of Carmine Alum fluorescence differed dramatically at emission wavelengths of 565–615 nm versus 650–710 nm. In the latter, a mostly epithelial (nuclear) visualization of Carmine Alum predominates. Autofluorescence with a peak emission of 495 nm was derived from the fixed and processed tissue itself as it was present in the unstained whole mount. Contribution of autofluorescence to the image decreases with increasing laser excitation wavelengths. SHG-B versus SHG-F signals revealed collagen fibers and could be found within single fibers, or in different fibers within the same layer. These differences presumably reflected different states of collagen fiber maturation. Loss of SHG signals from layer to layer could be ascribed to artifacts rendered by light scat

2013-01-01

297

Simultaneous Measurement of Neural Spike Recordings and Multi-Photon Calcium Imaging in Neuroblastoma Cells  

PubMed Central

This paper proposes the design and implementation of a micro-electrode array (MEA) for neuroblastoma cell culturing. It also explains the implementation of a multi-photon microscope (MPM) customized for neuroblastoma cell excitation and imaging under ambient light. Electrical signal and fluorescence images were simultaneously acquired from the neuroblastoma cells on the MEA. MPM calcium images of the cultured neuroblastoma cell on the MEA are presented and also the neural activity was acquired through the MEA recording. A calcium green-1 (CG-1) dextran conjugate of 10,000 D molecular weight was used in this experiment for calcium imaging. This study also evaluated the calcium oscillations and neural spike recording of neuroblastoma cells in an epileptic condition. Based on our observation of neural spikes in neuroblastoma cells with our proposed imaging modality, we report that neuroblastoma cells can be an important model for epileptic activity studies. PMID:23202210

Kim, Suhwan; Jung, Unsang; Baek, Juyeong; Kang, Shinwon; Kim, Jeehyun

2012-01-01

298

On-line screening of airborne PAH contamination by simultaneous multiphoton ionization and laser induced fluorescence  

SciTech Connect

In this preliminary study, the feasibility of on-line monitoring of sub-micron polycyclic aromatic hydrocarbon (PAH) aerosols by a combination of laser-induced-fluorescence (LIF) and laser multiphoton ionization (LMPI) techniques was investigated. For this purpose, an aerosol contaminated nitrogen gas was slowly bubbled through a quartz measurement chamber filled with hexane. Continuous PAH monitoring was maintained over two hours of the resultant concentration process. Simultaneous LIF and LMPI excitation was achieved by a pulsed dye laser, operated at 283 nm. For this wavelength, pyrene and naphthalene aerosols were used as target PAH materials. The resultant fluorescence light was collected by an optical fiber, while the LMPI signals were acquired by a pair of stainless steel electrodes immersed in the solution, allowing an automated readout of the photoionization current. The results indicate that PAH sub-micron aerosols, at an air concentration of 1 mg/m{sup 3}, can be monitored in this way.

Gridin, V.V.; Inoue, Takanori; Ogawa, Teiichiro; Schechter, I.

2000-04-01

299

The Near-Infrared Structure and Spectra of the Bipolar Nebulae M 2--9 and Afgl 2688: The Role of UV-Pumping and Shocks in Molecular Hydrogen Excitation  

E-print Network

High-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M~2--9 and AFGL 2688. The ability to spatially and spectrally resolve the various components of the nebulae has proved to be important in determining their physical structure and characteristics. In M~2--9, the lobes are found to have a double-shell structure. Analysis of \\h2\\ line ratios indicates that the \\h2\\ emission is radiatively excited. A well-resolved photodissociation region is observed in the lobes. The spectrum of the central source is dominated by H recombination lines and a strong continuum rising towards longer wavelengths consistent with a $T = 795$ K blackbody. In AFGL 2688, the emission from the bright lobes is mainly continuum reflected from the central star. Several molecular features from C$_2$ and CN are present. In the extreme end of the N lobe and in the E equatorial region, the emission is dominated by lines of \\h2 in the 2--2.5 \\microns region. The observed \\h2 line ratios indicate that the emission is collisionally excited, with an excitation temperature $T_{ex} \\approx 1600\\pm 100$ K.

Joseph L. Hora; William B. Latter

1994-08-03

300

Subcycle dynamics of high-order-harmonic generation of He atoms excited by attosecond pulses and driven by near-infrared laser fields: A self-interaction-free time-dependent density-functional-theory approach  

NASA Astrophysics Data System (ADS)

In the framework of the self-interaction-free time-dependent density-functional theory, we have performed three-dimensional (3D) ab initio calculations of He atoms in near-infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). We have explored the dynamical behavior of the subcycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. The oscillatory pattern in the photon emission spectra has a period of ˜1.3 fs which is half of the NIR laser optical cycle, similar to that recently measured in the experiments on transient absorption of He [M. Chini et al., Sci. Rep. 3, 1105 (2013), 10.1038/srep01105]. We present the photon emission spectra from 1s2p, 1s3p, 1s4p, 1s5p, and 1s6p excited states as functions of the time delay. We explore the subcycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several interesting features of the subcycle HHG dynamics and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra.

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2014-05-01

301

Evaluation of multiphoton effects in down-conversion  

SciTech Connect

Multiphoton effects in down-conversion are investigated based on the full-quantum multimode formalism by considering a three-level system as a prototype nonlinear system. We analytically derive the three-photon output wave function for two input photons, where one of the two input photons is down-converted and the other one is not. Using this output wave function, we calculate the down-conversion probability, the purity, and the fidelity to evaluate the entanglement between a down-converted photon pair and a non-down-converted photon. It is shown that the saturation effect occurs by multiphoton input and that it affects both the down-conversion probability and the quantum correlation between the down-converted photon pair and the non-down-converted photon. We also reveal the necessary conditions for multiphoton effects to be strong.

Yoshimi, Kazuyoshi [College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Ichikawa, Chiba 272-0827 (Japan); Koshino, Kazuki [College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Ichikawa, Chiba 272-0827 (Japan); PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan)

2010-04-15

302

Cold Multiphoton Matrix Assisted Laser Desorption/Ionization (MALDI)  

NASA Astrophysics Data System (ADS)

We present evidence of a cold multiphoton MALDI process occurring at a Room Temperature Ionic Liquid (RTIL)/metal interface. Our RTIL, 1-Butyl-3-methylimidazolium hexafluorophosphate, remains a stable liquid at room temperatures, even at pressures lower than 10-9 torr. We focus the 2^nd harmonic of a pulsed (2ns pulse length) Nd:YAG laser onto a gold grid coated with RTIL to generate a cold (narrow velocity spread) ion source with temporal resolution comparable to current MALDI ion sources. Unlike conventional MALDI, we believe multiphoton MALDI does not rely on collisional ionization within the ejection plume, and thus produces large signals at laser intensities just above threshold. Removing the collisional ionization process allow us to eject material from smaller regions of a sample, enhancing the suitability of multiphoton MALDI as an ion imaging technique.

Harris, Peter; Cooke, William; Tracy, Eugene

2008-05-01

303

Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection  

NASA Astrophysics Data System (ADS)

Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations. Qualitative agreement is observed between the experimental results and the theoretical calculations of the Legendre moments representing the angular distribution for the two enantiomers. The electron-ion coincidence technique using multiphoton ionization opens new directions in table-top analytical mass-spectrometric applications of mixtures of chiral molecules.

Lehmann, C. Stefan; Ram, N. Bhargava; Powis, Ivan; Janssen, Maurice H. M.

2013-12-01

304

Effect of multiphoton ionization on performance of crystalline lens.  

PubMed

This Letter presents a model for propagation of a laser pulse in a human crystalline lens. The model contains a transverse beam diffraction effect, laser-induced optical breakdown for the creation of plasma via a multiphoton ionization process, and the gradient index (GRIN) structure. Plasma introduces the nonlinearity in the crystalline lens which affects the propagation of the beam. The multiphoton ionization process generates plasma that changes the refractive index and hence leads to the defocusing of the laser beam. The Letter also points out the relevance of the present investigation to cavitation bubble formation for restoring the elasticity of the eyes. PMID:25502994

Gupta, Pradeep Kumar; Singh, Ram Kishor; Strickland, D; Campbell, M C W; Sharma, R P

2014-12-15

305

Nonlinear optical imaging characteristics of colonic adenocarcinoma using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy (MPM), a noninvasive optical method with high resolution and high sensitivity, can obtain detailed microstructures of biotissues at submolecular level. In this study, MPM is used to image microstructure varieties of human colonic mucosa and submucosa with adenocarcinoma. Some parameters, such as gland configuration, SHG/TPEF intensity ratio, and collagen orientation and so on, should serve the indicators of early colorectal cancer. The exploratory results show that it's potential for the development of multiphoton mini-endoscopy in real-time early diagnosis of colorectal cancer.

Liu, Nenrong; Chen, Rong; Li, Hongsheng; Chen, Jianxin

2012-12-01

306

Use of multi-photon laser-scanning microscopy to describe the distribution of xenobiotic chemicals in fish early life stages.  

PubMed

To better understand the mechanisms by which persistent bioaccumulative toxicants (PBTs) produce toxicity during fish early life stages (ELS), dose-response relationships need to be understood in relation to the dynamic distribution of chemicals in sensitive tissues. In this study, a multi-photon laser scanning microscope (MPLSM) was used to determine the multi-photon excitation spectra of several polyaromatic hydrocarbons (PAHs) and to describe chemical distribution among tissues during fish ELS. The multi-photon excitation spectra revealed intense fluorescent signal from the model fluorophore, pentamethyl-difluoro-boro-indacene (BODIPY), less signal from benzo[a]pyrene and fluoranthene, and no detectable signal from pyrene. The imaging method was tested by exposing newly fertilized medaka (Oryzias latipes) eggs to BODIPY or fluoranthene for 6 h, followed by transfer to clean media. Embryos and larvae were then imaged through 5 days post-hatch. The two test chemicals partitioned similarly throughout development and differences in fluorescence intensity among tissues were evident to a depth of several hundred microns. Initially, the most intense signal was observed in the oil droplet within the yolk, while a moderate signal was seen in the portion of the yolk containing the yolk-platelets. As embryonic development progressed, the liver biliary system, gall bladder, and intestinal tract accumulated strong fluorescent signal. After hatch, once the gastrointestinal tract was completely developed, most of the fluorescent signal was cleared. The MPLSM is a useful tool to describe the tissue distribution of fluorescent PBTs during fish ELS. PMID:15019246

Hornung, Michael W; Cook, Philip M; Flynn, Kevin M; Lothenbach, Doug B; Johnson, Rodney D; Nichols, John W

2004-03-30

307

Enhanced superradiance effect in a system of interacting two-level atoms and crossover from coherent to many-atom multiphoton relaxation regime  

NASA Astrophysics Data System (ADS)

We study effects of direct interatomic interaction on cooperative processes in atom-photon dynamics. Using a model of two-level atoms with Ising-type interaction as an example, it is demonstrated that interparticle interaction can promote cooperative radiative relaxation. For small number of atoms this results in inhibition of incoherent spontaneous decay leading to the regime of collective pulse relaxation. Above superradiance threshold increase in delay time and enhancement of superradiance is occurred. In the case of strong interaction (as compared to excitation energy of an atom) transition to the regime of multiphoton relaxation occurs, which we discuss using a simple model of two atoms in a high-Q single mode cavity. It is shown that such transition is accompanied by Rabi oscillations involving many-atom multiphoton states. Dephasing effect of dipole-dipole interaction and solitonic mechanism of relaxation are discussed as well.

Lukyanets, S.; Bevzenko, D.

2011-11-01

308

Detecting the imaging characteristics of colorectal carcinoma invading the muscularis propria with multiphoton microscopy Detecting the imaging characteristics of colorectal carcinoma  

NASA Astrophysics Data System (ADS)

The aim of this study was to examine the characteristics of the muscularis propria (mp) of human colorectum tissue with carcinoma invasion and help to advance the development for the diagnosis and therapy of early colorectal cancer. Multiphoton microscopic imaging system was used to achieve two-photon excited fluorescence (TPEF) and the second harmonic generation (SHG) images of samples respectively through the two-channel model. This work demonstrates the use of multiphoton microscopy (MPM) in obtaining clear images from thick layers of label-free tissues. Combined with endoscopy and miniaturization probes will be helpful for representing new methods to assess the functional behaviors of tissue and diagnose the early colorectal cancer in vivo.

Liu, N. R.; Chen, J. X.; Chen, G.; Yan, J.; Zhuo, S. M.; Jiang, X. S.

2012-02-01

309

Yb(3+)-doped GeS(2)-Ga2S(3)-CsCl glass with broad and adjustable absorption/excitation band for near-infrared luminescence.  

PubMed

The luminescent property of Yb(3+) ions in GeS(2)-Ga(2)S(3)-CsCl glasses with different CsCl contents has been studied. All the samples demonstrate a broad excitation band in the UV or/and visible range, depending on the composition, which is attributed to the charge transfer of the Yb(3+)-S(2-)/Cl(-) couple. The width of the excitation/absorption band can be as large as 150 nm. Moreover, with the increase of CsCl content, the peak position of the band can be continuously adjusted from 458 to 380 nm, due to the increase of the local average electronegativity around Yb(3+) ions. The broad and adjustable excitation band makes the Yb(3+)doped GeS(2)-Ga(2)S(3)-CsCl glass interesting for modifying the solar spectrum by absorbing strongly in the UV/blue region for emission around 1 ?m. This kind of material is the key to adapting the solar spectrum to the response of silicon photovoltaic solar cells. PMID:23811902

Fan, Bo; Xue, Bai; Zhang, Xianghua; Adam, Jean-Luc; Fan, Xianping

2013-07-01

310

Multiphoton ionization studies of WF6 and UF6  

NASA Astrophysics Data System (ADS)

Multiphoton ionization of UF6 and WF6 has been studied from low (approximately 10(exp 5) W/sq cm) to high (approximately 10(exp 16) W/sq cm) power density. The role of 'collective states' in MPI is considered.

Harkins, D. A.; Armstrong, D. P.; Compton, R. N.; Ding, Dajun

311

Fiber-based combined optical coherence and multiphoton endomicroscopy  

E-print Network

Fiber-based combined optical coherence and multiphoton endomicroscopy Gangjun Liu Zhongping Chen #12;Journal of Biomedical Optics 16(3), 036010 (March 2011) Fiber-based combined optical coherence. The efficiency can be further increased by fusing more multimode fibers with the DCF. Simultaneous optical

Chen, Zhongping

312

Generalized parity in multi-photon Rabi model  

E-print Network

Quantum multi--photon spin--boson model is considered. We solve an operator Riccati equation associated with that model and present a candidate for a generalized parity operator allowing to transform spin--boson Hamiltonian to a block diagonal form what indicates an existence of the related symmetry of the model.

Bart?omiej Gardas; Jerzy Dajka

2013-01-16

313

Multi-photon Rabi model: Generalized parity and its applications  

NASA Astrophysics Data System (ADS)

Quantum multi-photon spin-boson model is considered. We solve an operator Riccati equation associated with that model and present a candidate for a generalized parity operator allowing to transform spin-boson Hamiltonian to a block-diagonal form what indicates an existence of the related symmetry of the model.

Gardas, Bart?omiej; Dajka, Jerzy

2013-12-01

314

Infrared spectrum and molecular structure of lowest electronically excited triplet state of 1,4-dicyano-2,3,5,6-tetrafluorobenzene in low-temperature matrices  

NASA Astrophysics Data System (ADS)

An infrared spectrum of the T 1 state for 1,4-dicyano-2,3,5,6-tetrafluorobenzene in a low-temperature argon matrix was measured with a Fourier transform infrared spectrophotometer. The density-functional-theory calculation was performed to assign the observed bands. The optimized geometrical structure in the T 1 state is found to have two stable forms, planar ( D2 h) and non-planar ( C2 v), the former being more stable than the latter by 35.1 kJ mol -1. The T 1 state is identified as the planar form by a comparison of the observed matrix spectrum with the calculated spectral patterns. This assignment is confirmed by an analysis of the matrix-isolation phosphorescence spectra, where the observed vibronic bands are assigned to the fundamental and/or combination bands of the a g vibrational modes in analogy with those of 1,4-dicyanobenzene, where the T 1 structure belongs to D2 h symmetry.

Akai, Nobuyuki; Negishi, Daisuke; Kudoh, Satoshi; Takayanagi, Masao; Nakata, Munetaka

2004-01-01

315

Coherent Control of Multiphoton Transitions in the Gas and Condensed Phases with Shaped Ultrashort Pulses  

SciTech Connect

Controlling laser-molecule interactions has become an integral part of developing devices and applications in spectroscopy, microscopy, optical switching, micromachining and photochemistry. Coherent control of multiphoton transitions could bring a significant improvement of these methods. In microscopy, multi-photon transitions are used to activate different contrast agents and suppress background fluorescence; coherent control could generate selective probe excitation. In photochemistry, different dissociative states are accessed through two, three, or more photon transitions; coherent control could be used to select the reaction pathway and therefore the yield-specific products. For micromachining and processing a wide variety of materials, femtosecond lasers are now used routinely. Understanding the interactions between the intense femtosecond pulse and the material could lead to technologically important advances. Pulse shaping could then be used to optimize the desired outcome. The scope of our research program is to develop robust and efficient strategies to control nonlinear laser-matter interactions using ultrashort shaped pulses in gas and condensed phases. Our systematic research has led to significant developments in a number of areas relevant to the AMO Physics group at DOE, among them: generation of ultrashort phase shaped pulses, coherent control and manipulation of quantum mechanical states in gas and condensed phases, behavior of isolated molecules under intense laser fields, behavior of condensed phase matter under intense laser field and implications on micromachining with ultrashort pulses, coherent control of nanoparticles their surface plasmon waves and their nonlinear optical behavior, and observation of coherent Coulomb explosion processes at 10^16 W/cm^2. In all, the research has resulted in 36 publications (five journal covers) and nine invention disclosures, five of which have continued on to patenting

Marcos Dantus

2008-09-23

316

Silver nanoparticle based surface enhanced Raman scattering spectroscopy of diabetic and normal rat pancreatic tissue under near-infrared laser excitation  

NASA Astrophysics Data System (ADS)

This paper presents the use of high spatial resolution silver nanoparticle based near-infrared surface enhanced Raman scattering (SERS) from rat pancreatic tissue to obtain biochrmical information about the tissue. A high quality SERS signal from a mixture of pancreatic tissues and silver nanoparticles can be obtained within 10 s using a Renishaw micro-Raman system. Prominent SERS bands of pancreatic tissue were assigned to known molecular vibrations, such as the vibrations of DNA bases, RNA bases, proteins and lipids. Different tissue structures of diabetic and normal rat pancreatic tissues have characteristic features in SERS spectra. This exploratory study demonstrated great potential for using SERS imaging to distinguish diabetic and normal pancreatic tissues on frozen sections without using dye labeling of functionalized binding sites.

Huang, H.; Shi, H.; Feng, S.; Lin, J.; Chen, W.; Huang, Z.; Li, Y.; Yu, Y.; Lin, D.; Xu, Q.; Chen, R.

2013-04-01

317

Herschel Far-infrared Spectral-mapping of Orion BN/KL Outflows: Spatial Distribution of Excited CO, H2O, OH, O, and C+ in Shocked Gas  

NASA Astrophysics Data System (ADS)

We present ~2' × 2' spectral-maps of Orion Becklin-Neugebauer/Kleinmann-Low (BN/KL) outflows taken with Herschel at ~12'' resolution. For the first time in the far-IR domain, we spatially resolve the emission associated with the bright H2 shocked regions "Peak 1" and "Peak 2" from that of the hot core and ambient cloud. We analyze the ~54-310 ?m spectra taken with the PACS and SPIRE spectrometers. More than 100 lines are detected, most of them rotationally excited lines of 12CO (up to J = 48-47), H2O, OH, 13CO, and HCN. Peaks 1/2 are characterized by a very high L(CO)/L FIR ? 5 × 10–3 ratio and a plethora of far-IR H2O emission lines. The high-J CO and OH lines are a factor of ?2 brighter toward Peak 1 whereas several excited H2O lines are lsim50% brighter toward Peak 2. Most of the CO column density arises from T k ~ 200-500 K gas that we associate with low-velocity shocks that fail to sputter grain ice mantles and show a maximum gas-phase H2O/CO lsim 10–2 abundance ratio. In addition, the very excited CO (J > 35) and H2O lines reveal a hotter gas component (T k ~ 2500 K) from faster (v S > 25 km s–1) shocks that are able to sputter the frozen-out H2O and lead to high H2O/CO gsim 1 abundance ratios. The H2O and OH luminosities cannot be reproduced by shock models that assume high (undepleted) abundances of atomic oxygen in the preshock gas and/or neglect the presence of UV radiation in the postshock gas. Although massive outflows are a common feature in other massive star-forming cores, Orion BN/KL seems more peculiar because of its higher molecular luminosities and strong outflows caused by a recent explosive event. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Goicoechea, Javier R.; Chavarría, Luis; Cernicharo, José; Neufeld, David A.; Vavrek, Roland; Bergin, Edwin A.; Cuadrado, Sara; Encrenaz, Pierre; Etxaluze, Mireya; Melnick, Gary J.; Polehampton, Edward

2015-01-01

318

Multi-photon intracellular sodium imaging combined with UV-mediated focal uncaging of glutamate in CA1 pyramidal neurons.  

PubMed

Multi-photon fluorescence microscopy has enabled the analysis of morphological and physiological parameters of brain cells in the intact tissue with high spatial and temporal resolution. Combined with electrophysiology, it is widely used to study activity-related calcium signals in small subcellular compartments such as dendrites and dendritic spines. In addition to calcium transients, synaptic activity also induces postsynaptic sodium signals, the properties of which are only marginally understood. Here, we describe a method for combined whole-cell patch-clamp and multi-photon sodium imaging in cellular micro domains of central neurons. Furthermore, we introduce a modified procedure for ultra-violet (UV)-light-induced uncaging of glutamate, which allows reliable and focal activation of glutamate receptors in the tissue. To this end, whole-cell recordings were performed on Cornu Ammonis subdivision 1 (CA1) pyramidal neurons in acute tissue slices of the mouse hippocampus. Neurons were filled with the sodium-sensitive fluorescent dye SBFI through the patch-pipette, and multi-photon excitation of SBFI enabled the visualization of dendrites and adjacent spines. To establish UV-induced focal uncaging, several parameters including light intensity, volume affected by the UV uncaging beam, positioning of the beam as well as concentration of the caged compound were tested and optimized. Our results show that local perfusion with caged glutamate (MNI-Glutamate) and its focal UV-uncaging result in inward currents and sodium transients in dendrites and spines. Time course and amplitude of both inward currents and sodium signals correlate with the duration of the uncaging pulse. Furthermore, our results show that intracellular sodium signals are blocked in the presence of blockers for ionotropic glutamate receptors, demonstrating that they are mediated by sodium influx though this pathway. In summary, our method provides a reliable tool for the investigation of intracellular sodium signals induced by focal receptor activation in intact brain tissue. PMID:25350367

Kleinhans, Christian; Kafitz, Karl W; Rose, Christine R

2014-01-01

319

Multiphoton ionization and dissociation of diazirine: a theoretical and experimental study.  

PubMed

Multiphoton ionization and dissociation processes in diazirine have been studied experimentally via 304-325 nm two-photon absorption and theoretically by using the EOM-CCSD and B3LYP methods. The electronic structure calculations identified two excited valence states and four Rydberg states in the region 4.0-8.5 eV. In one-photon excitation, the strongest absorption is to the 2(1)A(1)(3p(x) <-- n) Rydberg state, whereas in two-photon absorption at comparable energies the first photon excites the low-lying 1(1)B(2) (pi* <-- n) valence state, from which the strongest absorption is to the dissociative valence 1(1)A(2) (pi* <-- sigma(NN)) state. The diazirine ion is calculated to be rather unstable, with a binding energy of only 0.73 eV and a geometry that resembles a weakly bound CH(2)(+)...N(2) complex. In the experimental studies, resonance-enhanced multiphoton ionization (REMPI) experiments show no ions at the parent diazirine mass but only CH(2)(+) ions from dissociative photoionization. It is proposed that weak one-photon absorption to the 1(1)B(2) state is immediately followed by more efficient absorption of another photon to reach the 1(1)A(2) state from which competition between ionization and fast dissociation takes place. Strong signals of CH(+) ions are also detected and assigned to 2 + 1 REMPI via the D(2)Pi (v' = 2) <-- <-- X(2)Pi (v'' = 0) two-photon transition of CH fragments. Velocity map CH(+) images show that CH(X, v'' = 0, N'') fragments are born with substantial translational energy, indicating that they arise from absorption of two photons in diazirine. It is argued that two-photon processes via the 1(1)B(2) intermediate state are very efficient in this wavelength range, leading predominantly to dissociation of diazirine from the 1(1)A(2) state. The most likely route to CH(X) formation is isomerization to isodiazirine followed by dissociation to CH + HN(2). In agreement with other theoretical papers, we recommend revisions of the heats of formation of diazirine and diazomethane. PMID:19341251

Fedorov, Igor; Koziol, Lucas; Mollner, Andrew K; Krylov, Anna I; Reisler, Hanna

2009-07-01

320

On the energetics of the lower excited states of N-methylpyrrole  

NASA Astrophysics Data System (ADS)

An absorption, fluorescence excitation, and (2+1) resonantly enhanced multiphoton ionization spectroscopic investigation was carried out on the lowest excited state of N-methylpyrrole (NMP). Transitions to and from this state were shown to give rise to the structured bands observed around 240 nm. An energy-dissipative channel was found that was only slightly higher in energy. Possible assignments of this channel in NMP and its relation to the states of pyrrole are discussed.

McDiarmid, R.; Xing, X.

1996-07-01

321

Detection of DCl by multiphoton ionization and determination of DCl and HCl internal state distributions  

NASA Astrophysics Data System (ADS)

A study of the 2+1 resonantly enhanced multiphoton ionization (REMPI) spectrum of DCl is reported. Transition energies for excitation of the F 1?-X 1?+ (0,0) and (1,0) bands, as well as the V 1?+-X 1?+(v',0) bands, for v'=15-19, are presented. The derived molecular constants for the F-X (0,0) and the V-X bands agree well with those previously obtained from analysis of the one-photon VUV absorption spectrum [A. E. Douglas and F. R. Greening, Can. J. Phys. 57, 1650 (1979)]. The ion signals for excitation through various rotational lines in the E-X (0,0) and F-X (0,0) and (1,0) bands are compared with theoretical two-photon line strengths. Extensive power- and J'-dependent ion fragmentation is observed for the former band. No fragmentation is observed in the F-X bands; however, the ion signal strengths are found to vary strongly with J'. This variation of REMPI signal strengths vs J' was shown to be due to an indirect predissociation, as in HCl. Tables of experimental line strength factors for the F-X (0,0) and (1,0) bands of HCl and DCl are reported. Finally, the relative REMPI detection sensitivities for HCl and DCl, through their respective F-X (0,0) R(1) lines, are compared.

Dagdigian, Paul J.; Varley, David F.; Liyanage, Rohana; Gordon, Robert J.; Field, Robert W.

1996-12-01

322

Ion-pair states of the ClO radical observed by multiphoton ionisation spectroscopy  

NASA Astrophysics Data System (ADS)

We present isotopically selected multiphoton ionisation spectra of the CIO radical following excitation in the wavelength range 276-261 nm, obtained using both a room-temperature sample and under the rotationally cold conditions in a pulsed molecular beam. In both cases high-resolution rotationally resolved spectra were obtained, with the 'cold' spectra showing discrete rovibrational bands. Analysis of the rotational structure leads to the identification of excited levels of ClO of 2? symmetry resonant at the two-photon energy (72200-76200 cm -1). These we deduce to possess extended equilibrium bond lengths ( R ? 2.4 Å), and thus associate with one or more ion-pair states. Full interpretation of the observed spectra is complicated by the effects of additional wavelength-dependent intensity enhancements due to predissociated levels of the A 2? state accidentally resonant at the energy of one absorbed photon. We report an isotopically resolved room-temperature 2 + 1 REMPI spectrum, involving a progression of vibrational levels of the previously documented C 2? state of ClO. The observed C?X two-photon transitions are well reproduced using known spectroscopic constants.

Cooper, Martin J.; Diez-Rojo, Trinidad; Rogers, Leon J.; Western, Colin M.; Ashfold, Michael N. R.; Hudgens, Jeffrey W.

1997-06-01

323

Evaluation of endogenous species involved in brain tumors using multiphoton photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

It has been shown that using non-resonant multiphoton photoacoustic spectroscopy (NMPPAS), excised brain tumor (grade III astrocytoma) and healthy tissue can be differentiated from each other, even in neighboring biopsy samples[1, 2]. Because of this, this powerful technique offers a great deal of potential for use as a surgical guidance technique for tumor margining with up to cellular level spatial resolution[3]. NMPPAS spectra are obtained by monitoring the non-radiative relaxation pathways via ultrasonic detection, following two-photon excitation with light in the optical diagnostic window (740nm-1100nm). Based upon significant differences in the ratiometric absorption of the tissues following 970nm and 1100nm excitation, a clear classification of the tissue can be made. These differences are the result of variations in composition and oxidation state of certain endogenous biochemical species between healthy and malignant tissues. In this work, NADH, NAD+ and ATP were measured using NMPPAS in model gelatin tissue phantoms to begin to understand which species might be responsible for the observed spectral differences in the tissue. Each species was placed in specific pH environments to provide control over the ratio of oxidized to reduced forms of the species. Ratiometric analyses were then conducted to account for variability caused due to instrumental parameters. This paper will discuss the potential roles of each of the species for tumor determination and their contribution to the spectral signature.

Dahal, Sudhir; Cullum, Brian M.

2013-05-01

324

N-H Stretching Excitations in Adenosine-Thymidine Base Pairs in Solution: Base Pair Geometries, Infrared Line Shapes and Ultrafast Vibrational Dynamics  

PubMed Central

We explore the N-H stretching vibrations of adenosine-thymidine base pairs in chloroform solution with linear and nonlinear infrared spectroscopy. Based on estimates from NMR measurements and ab initio calculations, we conclude that adenosine and thymidine form hydrogen bonded base pairs in Watson-Crick, reverse Watson-Crick, Hoogsteen and reverse Hoogsteen configurations with similar probability. Steady-state concentration- and temperature dependent linear FT-IR studies, including H/D exchange experiments, reveal that these hydrogen-bonded base pairs have complex N-H/N-D stretching spectra with a multitude of spectral components. Nonlinear 2D-IR spectroscopic results, together with IR-pump-IR-probe measurements, as also corroborated by ab initio calculations, reveal that the number of N-H stretching transitions is larger than the total number of N-H stretching modes. This is explained by couplings to other modes, such as an underdamped low-frequency hydrogen-bond mode, and a Fermi resonance with NH2 bending overtone levels of the adenosine amino-group. Our results demonstrate that modeling based on local N-H stretching vibrations only is not sufficient and call for further refinement of the description of the N-H stretching manifolds of nucleic acid base pairs of adenosine and thymidine, incorporating a multitude of couplings with fingerprint and low-frequency modes. PMID:23234439

Greve, Christian; Preketes, Nicholas K.; Fidder, Henk; Costard, Rene; Koeppe, Benjamin; Heisler, Ismael A.; Mukamel, Shaul; Temps, Friedrich; Nibbering, Erik T. J.; Elsaesser, Thomas

2013-01-01

325

Infrared cometary spectroscopy  

NASA Astrophysics Data System (ADS)

The recent observations and theoretical works concerning cometary molecules, relevant to infrared spectroscopy, are reviewed. Infrared spectroscopy, with microwave and submillimeter spectroscopy, is practically the only remote sensing technique able to study stable molecules sublimed from the nucleus or formed by gas phase chemistry in the inner comets. The recent observations of Comet Halley are considered. The observation of a strong and broad emission of CH-bearing molecules around 3.3 microns are discussed. The analysis shows that detailed models must include collisional excitation radiative transfer and chemical pumping. Considerations for the further evolution of infrared spectroscopy are given.

Crovisier, J.

1989-09-01

326

Characteristics of subgingival calculus detection by multiphoton fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Subgingival calculus has been recognized as a major cause of periodontitis, which is one of the main chronic infectious diseases of oral cavities and a principal cause of tooth loss in humans. Bacteria deposited in subgingival calculus or plaque cause gingival inflammation, function deterioration, and then periodontitis. However, subgingival calculus within the periodontal pocket is a complicated and potentially delicate structure to be detected with current dental armamentaria, namely dental x-rays and dental probes. Consequently, complete removal of subgingival calculus remains a challenge to periodontal therapies. In this study, the detection of subgingival calculus employing a multiphoton autofluorescence imaging method was characterized in comparison with a one-photon confocal fluorescence imaging technique. Feasibility of such a system was studied based on fluorescence response of gingiva, healthy teeth, and calculus with and without gingiva covered. The multiphoton fluorescence technology perceived the tissue-covered subgingival calculus that cannot be observed by the one-photon confocal fluorescence method.

Tung, Oi-Hong; Lee, Shyh-Yuan; Lai, Yu-Lin; Chen, How-Foo

2011-06-01

327

Multichannel multiphoton imaging of metal oxides nanoparticles in biological system  

NASA Astrophysics Data System (ADS)

Near-IR ultrafast pulse laser and confocal microscope are combined to create a multiphoton multichannel non-linear imaging technique, which allows in situ 3-D characterization of nonfluorescent nanoparticles in biological systems. We observed intense CARS signals generated from various metal oxides due to their high third-order nonlinear susceptibilities (Chi(3)), which do not depend on the vibrational resonance but on the electronic resonance. We show that fine and ultrafine particles of metal oxides in alveolar macrophage cells may be imaged in vitro using CARS and multiphoton fluorescence microscopy with highest optical resolution for extended periods without photobleaching effects. The advantage of the epi-detection over the forward detection for imaging sub-micron particles has been investigated.

Zheng, Yuangang; Holtom, Gary; Colson, Steven D.

2004-06-01

328

Tunable multiphoton Rabi oscillations in an electronic spin system  

NASA Astrophysics Data System (ADS)

We report on multiphoton Rabi oscillations and controlled tuning of a multilevel system at room temperature (S=5/2 for Mn2+:MgO) in and out of a quasiharmonic level configuration. The anisotropy is much smaller than the Zeeman splittings, e.g., the six-level scheme shows only a small deviation from an equidistant diagram. This allows us to tune the spin dynamics by compensating for the cubic anisotropy with either a precise static-field orientation or a microwave field intensity. Using the rotating-frame approximation, the experiments are explained very well by both an analytical model and a generalized numerical model. The calculated multiphoton Rabi frequencies are in excellent agreement with the experimental data.

Bertaina, S.; Groll, N.; Chen, L.; Chiorescu, I.

2011-10-01

329

Near-infrared excited state dynamics of melanins: the effects of iron content, photo-damage, chemical oxidation, and aggregate size.  

PubMed

Ultrafast pump-probe measurements can discriminate the two forms of melanin found in biological tissue (eumelanin and pheomelanin), which may be useful for diagnosing and grading melanoma. However, recent work has shown that bound iron content changes eumelanin's pump-probe response, making it more similar to that of pheomelanin. Here we record the pump-probe response of these melanins at a wider range of wavelengths than previous work and show that with shorter pump wavelengths the response crosses over from being dominated by ground-state bleaching to being dominated by excited-state absorption. The crossover wavelength is different for each type of melanin. In our analysis, we found that the mechanism by which iron modifies eumelanin's pump-probe response cannot be attributed to Raman resonances or differences in melanin aggregation and is more likely caused by iron acting to broaden the unit spectra of individual chromophores in the heterogeneous melanin aggregate. We analyze the dependence on optical intensity, finding that iron-loaded eumelanin undergoes irreversible changes to the pump-probe response after intense laser exposure. Simultaneously acquired fluorescence data suggest that the previously reported "activation" of eumelanin fluorescence may be caused in part by the dissociation of metal ions or the selective degradation of iron-containing melanin. PMID:24446774

Simpson, Mary Jane; Wilson, Jesse W; Robles, Francisco E; Dall, Christopher P; Glass, Keely; Simon, John D; Warren, Warren S

2014-02-13

330

Near-Infrared Excited State Dynamics of Melanins: The Effects of Iron Content, Photo-Damage, Chemical Oxidation, and Aggregate Size  

PubMed Central

Ultrafast pump–probe measurements can discriminate the two forms of melanin found in biological tissue (eumelanin and pheomelanin), which may be useful for diagnosing and grading melanoma. However, recent work has shown that bound iron content changes eumelanin’s pump–probe response, making it more similar to that of pheomelanin. Here we record the pump–probe response of these melanins at a wider range of wavelengths than previous work and show that with shorter pump wavelengths the response crosses over from being dominated by ground-state bleaching to being dominated by excited-state absorption. The crossover wavelength is different for each type of melanin. In our analysis, we found that the mechanism by which iron modifies eumelanin’s pump–probe response cannot be attributed to Raman resonances or differences in melanin aggregation and is more likely caused by iron acting to broaden the unit spectra of individual chromophores in the heterogeneous melanin aggregate. We analyze the dependence on optical intensity, finding that iron-loaded eumelanin undergoes irreversible changes to the pump–probe response after intense laser exposure. Simultaneously acquired fluorescence data suggest that the previously reported “activation” of eumelanin fluorescence may be caused in part by the dissociation of metal ions or the selective degradation of iron-containing melanin. PMID:24446774

2015-01-01

331

Vectorizable wave propagation FORTRANcode for calculations of multiphoton dissociation  

NASA Astrophysics Data System (ADS)

A vectorizable FORTRAN code for the ETA10 or other vector machines for numerical calculation of the time-dependent Schrödinger equation is presented. Preliminary results for the multiphoton dissociation of nitrogen oxide are shown. The applied electric field was approximated by a classical sinusoidal wave; both sinusoidal and cosinusoidal wave forms were tested, and the internuclear potential was taken to be a Morse function. Dissociation histories of three types were found.

Ting, Julian J.-L.; Yuan, J. M.; Jiang, T.-F.

1992-06-01

332

XUV multiphoton process by high-order harmonics  

Microsoft Academic Search

We report on the generation of intense femtosecond pulses in the soft X-ray region and their application to the the multi-photon processes with a nonlinear interaction between an atom and photons in the soft Xray. 1 Harmonic generation The high-order harmonics generated with femtosecond laser pulses is one of the promising light sources of the intense XUV[1]?soft X-ray. They have

Yasuo Nabekawa; E. J. Takahashi; Hirokazu Hasegawa; Katumi Midorikawa

2005-01-01

333

Quantum radiation reaction effects in multiphoton Compton scattering  

E-print Network

Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

A. Di Piazza; K. Z. Hatsagortsyan; C. H. Keitel

2010-11-24

334

Human hepatocellular carcinoma diagnosis by multiphoton autofluorescence microscopy  

NASA Astrophysics Data System (ADS)

Conventionally, the diagnosis of hepatocellular carcinoma (HCC) is performed by qualitative examination of histopathological specimens, which takes times for sample preparation in fixation, section and stain. Our objective is to demonstrate an effective and efficient approach to apply multiphoton microscopy imaging the HCC specimens, with the advantages of being optical section, label-free, subcellular resolution, minimal invasiveness, and the acquisition of quantitative information at the same time. The imaging modality of multiphoton autofluorescence (MAF) was used for the qualitative imaging and quantitative analysis of HCC of different grades under ex-vivo, label-free conditions. We found that while MAF is effective in identifying cellular architecture in the liver specimens, and obtained quantitative parameters in characterizing the disease. Our results demonstrates the capability of using tissue quantitative parameters of multiphoton autofluorescence (MAF), the nuclear number density (NND), and nuclear-cytoplasmic ratio (NCR) for tumor discrimination and that this technology has the potential in clinical diagnosis of HCC and the in-vivo investigation of liver tumor development in animal models.

Sun, Tzu-Lin; Liu, Yuan; Sung, Ming-Chin; Chen, Hsiao-Ching; Yang, Chuen-Huei; Hovhannisyan, Vladimir; Chiou, Ling-Ling; Lin, Wei-Chou; Huang, Guan-Tarn; Kim, Ki-Hean; So, Peter T. C.; Lin, Chih-Ju; Lee, Hsuan-Shu; Dong, Chen-Yuan

2010-02-01

335

Intracavity system design for IR multiphoton dissociation  

NASA Astrophysics Data System (ADS)

An intracavity system for the infrared multiple photon dissociation (IRMPD) of molecules with high dissociation energy threshold has been designed and implemented. The system design based on a TEA CO2 laser with a cavity folded in V-shape included the analysis of its stability varying the cavity dimensions as well as the analysis of the positions of the beam waists and of the beam size at them. The intracavity energy as a function of the total sample pressure has been measured and the laser-operation threshold has been determined. Intracavity IRMPD has been compared to traditional IRMPD performed in an irradiation geometry in which the radiation is focused into a photoreactor placed outside the laser cavity. Dissociation volumes in intracavity irradiation have resulted an order of magnitude larger than those obtained in experiments performed with the photoreactor outside the laser cavity.

Freytes, V. M.; Codnia, J.; Azcárate, M. L.

2011-06-01

336

July 1987 / Vol. 12, No. 7 / OPTICS LETTERS 489 Optical high-order subharmonic excitation of free cyclotron  

E-print Network

multiphoton excitation of a cyclo- tron electron driven by biharmonic laser radiation with optical frequencies Adand '02such that co,- 02 Qe(three-photon resonance) or ah - c02 - 2Q, (four- photon resonance resonant nonlinear systems. For example, in a simple nonlinear circuit using a biased diode as a non

Kaplan, Alexander

337

Exciting flavored bound states  

NASA Astrophysics Data System (ADS)

We study ground and radial excitations of flavor singlet and flavored pseudoscalar mesons within the framework of the rainbow-ladder truncation using an infrared massive and finite interaction in agreement with recent results for the gluon-dressing function from lattice QCD and Dyson-Schwinger equations. Whereas the ground-state masses and decay constants of the light mesons as well as charmonia are well described, we confirm previous observations that this truncation is inadequate to provide realistic predictions for the spectrum of excited and exotic states. Moreover, we find a complex conjugate pair of eigenvalues for the excited D(s) mesons, which indicates a non-Hermiticity of the interaction kernel in the case of heavy-light systems and the present truncation. Nevertheless, limiting ourselves to the leading contributions of the Bethe-Salpeter amplitudes, we find a reasonable description of the charmed ground states and their respective decay constants.

Rojas, E.; El-Bennich, B.; de Melo, J. P. B. C.

2014-10-01

338

A multimodal multiphoton microscope for biological imaging  

NASA Astrophysics Data System (ADS)

We report on the construction of a highly flexible system for advanced biological imaging, where all the following imaging techniques are integrated into the same microscope: Coherent anti-Stokes Raman scattering (CARS), two photon excitation fluorescence (TPEF), second harmonic generation (SGH), sum frequency generation (SFG), fluorescence lifetime imaging (FLIM) and differential interference contrast (DIC). The system employs a Nd:YVO4 laser as pump (7 ps, 1064 nm), and two tunable OPOs (6 ps, 700 - 1000 nm). Our microscope comprises a heater stage and perfusion cell for imaging of live cells, and features an atomic force microscope (AFM) which enables optical imaging at 10 nm resolution. Multimodal imaging of breast cancer cells and tissue will be demonstrated as well as imaging of anticancer drugs in living cells.

Mouras, Rabah; Downes, Andrew; Rischitor, Grigore; Mari, Meropi; Elfick, Alistair

2010-02-01

339

UNIT 12.10Detecting Protein-Protein Interactions In Vivo with FRET using Multiphoton  

E-print Network

UNIT 12.10Detecting Protein-Protein Interactions In Vivo with FRET using Multiphoton Fluorescence in vivo based on the measurement of FRET using the multiphoton fluorescence lifetime imaging microscopy (FLIM) technique. By using the FLIM-FRET technique, the spatial organization and quantification

Lamond, Angus I.

340

Infrared Astronomy  

NSDL National Science Digital Library

NASA's Infrared Processing and Analysis Center (IPAC) provides the Infrared Astronomy Website as one of its outreach programs. Infrared Astronomy, or "the detection and study of the infrared radiation (heat energy) emitted from objects in the Universe," is described and placed in context in the sections Discovery of Infrared, What is Infrared, Infrared Astronomy, Background, and the Infrared Universe. For current information, see the News & Discoveries, Active/ Future Projects, and Activities sections; past and current projects supported by IPAC are featured in the Infrared Gallery. The site targets a broad audience and is geared towards many learning levels.

341

Temporal focusing with spatially modulated excitation.  

PubMed

Temporal focusing of ultrashort pulses has been shown to enable wide-field depth-resolved two-photon fluorescence microscopy. In this process, an entire plane in the sample is selectively excited by introduction of geometrical dispersion to an ultrashort pulse. Many applications, such as multiphoton lithography, uncaging or region-of-interest imaging, require, however, illumination patterns which significantly differ from homogeneous excitation of an entire plane in the sample. Here we consider the effects of such spatial modulation of a temporally focused excitation pattern on both the generated excitation pattern and on its axial confinement. The transition in the axial response between line illumination and wide-field illumination is characterized both theoretically and experimentally. For 2D patterning, we show that in the case of amplitude-only modulation the axial response is generally similar to that of wide-field illumination, while for phase-and-amplitude modulation the axial response slightly deteriorates when the phase variation is rapid, a regime which is shown to be relevant to excitation by beams shaped using spatial light modulators. Finally, general guidelines for the use of spatially modulated temporally focused excitation are presented. PMID:19333304

Papagiakoumou, Eirini; de Sars, Vincent; Emiliani, Valentina; Oron, Dan

2009-03-30

342

Multiphoton microscopic imaging of histological sections without hematoxylin and eosin staining differentiates carcinoma in situ lesion from normal oesophagus  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy (MPM) has become a powerful, important tool for tissues imaging at the molecular level. In this paper, this technique was extended to histological investigations, differentiating carcinoma in situ (CIS) lesion from normal oesophagus by imaging histological sections without hematoxylin and eosin (H&E) staining. The results show that the histology procedures of dehydration, paraffin embedding, and de-paraffinizing highlighted two photon excited fluorescence of cytoplasm and nucleolus of epithelial cell and collagen in stroma. MPM has the ability to identify the characteristics of CIS lesion including changes of squamous cells and full epithelium, identification of basement membrane, especially prominent nucleolus. The studies described here show that MPM has the potential for future retrospective studies of tumor staging by employing on histological section specimens without H&E staining.

Chen, Jianxin; Xu, Jian; Kang, Deyong; Xu, Meifang; Zhuo, Shuangmu; Zhu, Xiaoqin; Jiang, Xingshan

2013-10-01

343

In vivo three-dimensional optical coherence tomography and multiphoton microscopy in a mouse model of ovarian neoplasia  

NASA Astrophysics Data System (ADS)

Our goal is to use optical coherence tomography (OCT) and multiphoton microscopy (MPM) to detect early tumor development in a mouse model of ovarian neoplasia. We hope to use information regarding early tumor development to create a diagnostic test for high-risk patients. In this study we collect in vivo images using OCT, second harmonic generation and two-photon excited fluorescence from non-vinylcyclohexene diepoxide (VCD)-dosed and VCD-dosed mice. VCD causes follicular apoptosis (simulating menopause) and leads to tumor development. Using OCT and MPM we visualized the ovarian microstructure and were able to see differences between non-VCD-dosed and VCD-dosed animals. This leads us to believe that OCT and MPM may be useful for detecting changes due to early tumor development.

Watson, Jennifer M.; Marion, Samuel L.; Rice, Photini Faith; Bentley, David L.; Besselsen, David; Utzinger, Urs; Hoyer, Patricia B.; Barton, Jennifer K.

2013-03-01

344

Effect of laser spectral bandwidth on coherent control of resonance-enhanced multiphoton-ionization photoelectron spectroscopy  

SciTech Connect

The high-resolution (2 + 1) resonance-enhanced multiphoton-ionization photoelectron spectroscopy (REMPI-PS) can be obtained by measuring the photoelectron intensity at a given kinetic energy and scanning the single ? phase step position. In this paper, we further demonstrate that the high-resolution (2 + 1) REMPI-PS cannot be achieved at any measured position of the kinetic energy by this measurement method, which is affected by the laser spectral bandwidth. We propose a double ? phase step modulation to eliminate the effect of the laser spectral bandwidth, and show the advantage of the double ? phase step modulation on achieving the high-resolution (2 + 1) REMPI-PS by considering the contributions involving on- and near-resonant three-photon excitation pathways.

Xu, Shuwu [State Key Laboratory of Precision Spectroscopy, and Department of Physics, East China Normal University, Shanghai 200062 (China) [State Key Laboratory of Precision Spectroscopy, and Department of Physics, East China Normal University, Shanghai 200062 (China); School of Science, Nantong University, Nantong 226007 (China); Ding, Jingxin, E-mail: jxding@phy.ecnu.edu.cn; Lu, Chenhui; Jia, Tianqing; Zhang, Shian, E-mail: sazhang@phy.ecnu.edu.cn; Sun, Zhenrong [State Key Laboratory of Precision Spectroscopy, and Department of Physics, East China Normal University, Shanghai 200062 (China)] [State Key Laboratory of Precision Spectroscopy, and Department of Physics, East China Normal University, Shanghai 200062 (China)

2014-02-28

345

Polarization of molecular targets using infrared stimulated Raman adiabatic Nandini Mukherjee and Richard N. Zarea  

E-print Network

Polarization of molecular targets using infrared stimulated Raman adiabatic passage Nandini polarized infrared excitation biaxial excitation . Specifically, the perpendicular polarization connects the v=1 intermediate level to the final vibrational level v=2, and the parallel polarization connects

Zare, Richard N.

346

Snapshot coherence-gated direct wavefront sensing for multi-photon microscopy.  

PubMed

Deep imaging in turbid media such as biological tissue is challenging due to scattering and optical aberrations. Adaptive optics has the potential to compensate the tissue aberrations. We present a wavefront sensing scheme for multi-photon scanning microscopes using the pulsed, near-infrared light reflected back from the sample utilising coherence gating and a confocal pinhole to isolate the light from a layer of interest. By interfering the back-reflected light with a tilted reference beam, we create a fringe pattern with a known spatial carrier frequency in an image of the back-aperture plane of the microscope objective. The wavefront aberrations distort this fringe pattern and thereby imprint themselves at the carrier frequency, which allows us to separate the aberrations in the Fourier domain from low spatial frequency noise. A Fourier analysis of the modulated fringes combined with a virtual Shack-Hartmann sensor for smoothing yields a modal representation of the wavefront suitable for correction. We show results with this method correcting both DM-induced and sample-induced aberrations in rat tail collagen fibres as well as a Hoechst-stained MCF-7 spheroid of cancer cells. PMID:24787857

van Werkhoven, T I M; Antonello, J; Truong, H H; Verhaegen, M; Gerritsen, H C; Keller, C U

2014-04-21

347

Identification of non-neoplastic and neoplastic gastric polyps using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Gastric polyps can be broadly defined as luminal lesions projecting above the plane of the mucosal surface. They are generally divided into non-neoplastic and neoplastic polyps. Accurate diagnosis of neoplastic polyps is important because of their well-known relationship with gastric cancer. Multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) is one of the most important recent inventions in biological imaging. In this study, we used MPM to image the microstructure of gastric polyps, including fundic gland polyps, hyperplastic polyps, inflammatory fibroid polyps and adenomas, then compared with gold-standard hematoxylin- eosin(H-E)-stained histopathology. MPM images showed that different gastric polyps have different gland architecture and cell morphology. Dilated, elongated or branch-like hyperplastic polyps are arranged by columnar epithelial cells. Inflammatory fibroid polyps are composed of small, thin-walled blood vessels surrounded by short spindle cells. Fundic glands polyps are lined by parietal cells and chief cells, admixed with normal glands. Gastric adenomas are generally composed of tubules or villi of dysplastic epithelium, which usually show some degree of intestinal-type differentiation toward absorptive cells, goblet cells, endocrine cells. Our results demonstrated that MPM can be used to identify non- neoplastic and neoplastic gastric polyps without the need of any staining procedure.

Jiang, Shanghai; Kang, Deyong; Xu, Meifang; Zhu, Xiaoqin; Zhuo, Shuangmu; Chen, Jianxin

2012-12-01

348

Ultrasensitive standoff chemical sensing based on nonlinear multi-photon laser wave-mixing spectroscopy  

NASA Astrophysics Data System (ADS)

Nonlinear multi-photon laser wave mixing is presented as an ultrasensitive optical detection method for chem/bio agents in thin films and gas- and liquid-phase samples. Laser wave mixing is an unusually sensitive optical absorption-based detection method that offers significant inherent advantages including excellent sensitivity, small sample requirements, short optical path lengths, high spatial resolution, high spectral resolution and standoff remote detection capability. Wave mixing can detect trace amounts of chemicals even when using micrometer-thin samples, and hence, it can be conveniently interfaced to fibers, microarrays, microfluidic systems, lab-on-a-chip, capillary electrophoresis and other capillary- or fiber-based chemical separation systems. The wave-mixing signal is generated instantaneously as the two input laser beams intersect inside the analyte of interest. Laser excitation wavelengths can be tuned to detect multiple chemicals in their native form since wave mixing can detect both fluorescing and non-fluorescing samples at parts-pertrillion or better detection sensitivity levels. The wave-mixing signal is a laser-like coherent beam, and hence, it allows reliable and effective remote sensing of chemicals. Sensitive wave-mixing detectors offer many potential applications including sensitive detection of biomarkers, early detection of diseases, sensitive monitoring of environmental samples, and reliable detection of hazardous chem/bio agents with a standoff detection capability.

Gregerson, Marc; Hetu, Marcel; Iwabuchi, Manna; Jimenez, Jorge; Warren, Ashley; Tong, William G.

2012-10-01

349

Optical tweezers and multiphoton microscopies integrated photonic tool for mechanical and biochemical cell processes studies  

NASA Astrophysics Data System (ADS)

The research in biomedical photonics is clearly evolving in the direction of the understanding of biological processes at the cell level. The spatial resolution to accomplish this task practically requires photonics tools. However, an integration of different photonic tools and a multimodal and functional approach will be necessary to access the mechanical and biochemical cell processes. This way we can observe mechanicaly triggered biochemical events or biochemicaly triggered mechanical events, or even observe simultaneously mechanical and biochemical events triggered by other means, e.g. electricaly. One great advantage of the photonic tools is its easiness for integration. Therefore, we developed such integrated tool by incorporating single and double Optical Tweezers with Confocal Single and Multiphoton Microscopies. This system can perform 2-photon excited fluorescence and Second Harmonic Generation microscopies together with optical manipulations. It also can acquire Fluorescence and SHG spectra of specific spots. Force, elasticity and viscosity measurements of stretched membranes can be followed by real time confocal microscopies. Also opticaly trapped living protozoas, such as leishmania amazonensis. Integration with CARS microscopy is under way. We will show several examples of the use of such integrated instrument and its potential to observe mechanical and biochemical processes at cell level.

de Thomaz, A. A.; Faustino, W. M.; Fontes, A.; Fernandes, H. P.; Barjas-Castro, M. d. L.; Metze, K.; Giorgio, S.; Barbosa, L. C.; Cesar, C. L.

2007-09-01

350

Multifocal multiphoton microscopy based on a spatial light modulator  

PubMed Central

We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware. PMID:23894222

Shao, Y.; Qin, W.; Liu, H.; Peng, X.; Niu, H.

2013-01-01

351

Statistics of multiphoton events in spontaneous parametric down-conversion  

E-print Network

We present an experimental characterization of the statistics of multiple photon pairs produced by spontaneous parametric down-conversion realized in a nonlinear medium pumped by high-energy ultrashort pulses from a regenerative amplifier. The photon number resolved measurement has been implemented with the help of a fiber loop detector. We introduce an effective theoretical description of the observed statistics based on parameters that can be assigned direct physical nterpretation. These parameters, determined for our source from the collected experimental data, characterize the usefulness of down-conversion sources in multiphoton interference schemes that underlie protocols for quantum information processing and communication.

Wojciech Wasilewski; Czeslaw Radzewicz; Robert Frankowski; Konrad Banaszek

2008-05-12

352

Multiphoton ionization of ions, neutrals, and clusters. Progress report  

SciTech Connect

Scientific results are summarized from a three year research program on multiphoton ionization in aromatic molecules, clusters, and their ions. As originally proposed, the studies elucidated a new cluster ionization mechanism, characterized properties of long range intermolecular interactions, and investigated electronic transitions of aromatic cations cooled in a supersonic beam. The studies indicate that the new cluster ionization mechanism is highly efficient and dominates conventional 1 + 1 resonant ionization. In the case of the dimer of the large aromatic molecule fluorene, the results suggest that excimer formation competes with a direct ionization process. Highly selective excitonic spectra have been identified for several cluster species.

Wessel, J.

1991-06-28

353

Nonperturbative multiphoton electron-positron-pair creation in laser fields  

SciTech Connect

A detailed analysis of electron-positron-pair creation from vacuum in counterpropagating laser pulses is presented. Our particular interest lies in the nonperturbative multiphoton regime of interaction in different frequency domains. The pair creation may proceed both resonantly and nonresonantly where characteristic Rabi oscillations are shown for the near-resonance. By means of a quasiclassical method we obtain intuitive physical insight into the process. An independent numerical approach confirms and extends the analytical results by providing rich information on momentum spectra, resonance widths, and the time dependence of the creation probability, both on and off the resonance.

Mocken, Guido R.; Ruf, Matthias; Mueller, Carsten; Keitel, Christoph H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2010-02-15

354

Microstructure imaging of human rectal mucosa using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy (MPM) has high resolution and sensitivity. In this study, MPM was used to image microstructure of human rectal mucosa. The morphology and distribution of the main components in mucosa layer, absorptive cells and goblet cells in the epithelium, abundant intestinal glands in the lamina propria and smooth muscle fibers in the muscularis mucosa were clearly monitored. The variations of these components were tightly relevant to the pathology in gastrointestine system, especially early rectal cancer. The obtained images will be helpful for the diagnosis of early colorectal cancer.

Liu, N. R.; Chen, G.; Chen, J. X.; Yan, J.; Zhuo, S. M.; Zheng, L. Q.; Jiang, X. S.

2011-01-01

355

Atomic force microscopy based, multiphoton, photoelectron emission imaging  

SciTech Connect

Images of photoelectron emission from metallic surfaces were obtained with a modified atomic force microscope operating in air. Illumination of the samples was achieved in the near field of a metal-coated microcantilever tip, placed in the beam of a femtosecond pulsed laser that is incident at a grazing angle with respect to the sample surface. Photoelectron currents were measured through the tip with a prototype amplifier. The power law dependence of average photocurrent on light intensity is compatible with multiphoton photoelectric effect and the work function of the metal covering a particular area on the two-metal patterned samples used.

Spanakis, E.; Chimmalgi, A.; Stratakis, E.; Grigoropoulos, C. P.; Fotakis, C.; Tzanetakis, P. [Institute of Electronic Structure and Lasers, Foundation for Research and Technology Hellas (IESL-FORTH), Heraklion 71110 (Greece); Materials Science and Technology Department, University of Crete, Heraklion 71003 (Greece); and Technological Educational Institute of Crete, Heraklion 71004 (Greece); Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Institute of Electronic Structure and Lasers, Foundation for Research and Technology Hellas (IESL-FORTH), Heraklion 71110 (Greece); Materials Science and Technology Department, University of Crete, Heraklion 71003 (Greece); and Technological Educational Institute of Crete, Heraklion 71004 (Greece); Department of Mechanical Engineering, University of California, Berkeley, California 94720-1740 (United States); Institute of Electronic Structure and Lasers, Foundation for Research and Technology Hellas (IESL-FORTH), Heraklion 71110 (Greece) and Physics Department, University of Crete, Heraklion 71409 (Greece)

2006-07-03

356

Excite Travel  

NSDL National Science Digital Library

Excite Travel is one of the most comprehensive international guides to communities around the world. Excite Travel provides easy and timely access to information on travel, entertainment, and local business, plus government and community services for all regions of the world.

357

Far-Infrared Graphene Plasmonic Crystals for Plasmonic Band Engineering  

E-print Network

transform infrared spectroscopy demonstrates band formation, where far-infrared irradiation excites a uniqueFar-Infrared Graphene Plasmonic Crystals for Plasmonic Band Engineering Kitty Y. M. Yeung, Jingyee Supporting Information ABSTRACT: We introduce far-infrared graphene plasmonic crystals. Periodic structural

Ham, Donhee

358

Infrared Investigations  

NSDL National Science Digital Library

In this activity, learners explore how infrared technology is used by engineers to create equipment and systems for a variety of industries. Learners explore the application of infrared in remote controls, test materials that encourage or prevent infrared transmission, and develop systems that allow transmission of infrared in restricted environments.

Ieee

2013-08-30

359

Infrared Investigations.  

ERIC Educational Resources Information Center

Describes a series of simple and nontraditional experiments that enable students to discover the properties of infrared radiation by studying the propagation, reflection, diffusion, and refraction of infrared. The experiments rely on two modules, an infrared transmitter and an infrared receiver. (SAH)

Lascours, Jean; Albe, Virginie

2001-01-01

360

Multiphoton fluorescence recovery after photobleaching in bounded systems  

NASA Astrophysics Data System (ADS)

Multiphoton fluorescence recovery after photobleaching (MP-FRAP) is a laser microscopy technique used to measure diffusion coefficients of macromolecules in biological systems. The three-dimensional resolution and superior depth penetration within scattering samples offered by MP-FRAP make it an important tool for investigating both in vitro and in vivo systems. However, biological systems frequently confine diffusion within solid barriers, and to date the effect of such barriers on the measurement of absolute diffusion coefficients via MP-FRAP has not been studied. We have used Monte Carlo simulations of diffusion and MP-FRAP to understand the effect of barriers of varying geometries and positions relative to the two-photon focal volume. Furthermore, we supply ranges of barrier positions within which MP-FRAP can confidently be employed to measure accurate diffusion coefficients. Finally, we produce two new MP-FRAP models that can produce accurate diffusion coefficients in the presence of a single plane boundary or parallel infinite plane boundaries positioned parallel to the optical axis, up to the resolution limit of the multiphoton laser scanning microscope.

Sullivan, Kelley D.; Brown, Edward B.

2011-05-01

361

Multifocal multiphoton microscopy based on multianode photomultiplier tubes  

PubMed Central

Multifocal multiphoton microscopy (MMM) enhances imaging speed by parallelization. It is not well understood why the imaging depth of MMM is significantly shorter than conventional single-focus multiphoton microscopy (SMM). In this report, we show that the need for spatially resolved detectors in MMM results in a system that is more sensitive to the scattering of emission photons with reduced imaging depth. For imaging depths down to twice the scattering mean free path length of emission photons (2×lsem), the emission point spread function (PSFem) is found to consist of a narrow, diffraction limited distribution from ballistic emission photons and a broad, relatively low amplitude distribution from scattered photons. Since the scattered photon distribution is approximately 100 times wider than that of the unscattered photons at 2×lsem, image contrast and depth are degraded without compromising resolution. To overcome the imaging depth limitation of MMM, we present a new design that replaces CCD cameras with multi-anode photomultiplier tubes (MAPMTs) allowing more efficient collection of scattered emission photons. We demonstrate that MAPMT-based MMM has imaging depth comparable to SMM with equivalent sensitivity by imaging tissue phantoms, ex vivo human skin specimens based on endogenous fluorophores, and green fluorescent protein (GFP) expressing neurons in mouse brain slices. PMID:19547526

Kim, Ki Hean; Buehler, Christof; Bahlmann, Karsten; Ragan, Timothy; Lee, Wei-Chung A.; Nedivi, Elly; Heffer, Erica L.; Fantini, Sergio; So, Peter T. C.

2011-01-01

362

Fringe-free, Background-free, Collinear Third Harmonic Generation FROG Measurements for Multiphoton Microscopy  

SciTech Connect

Collinear pulse measurement tools useful at the full numerical aperture (NA) of multiphoton microscope objectives are a necessity for a quantitative characterization of the femtosecond pulses focused by these systems. In this letter, we demonstrate a simple new technique, for characterizing the pulse at the focus in a multiphoton microscope. This technique, a background-free, fringe-free, form of frequency-resolved optical gating, uses the third harmonic signal generated from a glass coverslip. Here it is used to characterize 100 fs pulses (typical values for a multiphoton microscope) at the focus of a 0.65 NA objective.

Chadwick, R; Spahr, E; Squier, J A; Durfee, C G; Walker, B C; Fittinghoff, D N

2006-07-21

363

Addressable discrete-line-scanning multiphoton microscopy based on a spatial light modulator  

PubMed Central

We developed a novel addressable discrete-line-scanning multiphoton microscope with high lateral and axial resolutions based on a spatial light modulator. Our discrete-line-focus design eliminates the cross talk that occurs in conventional one-dimensional line-scanning multiphoton microscopies. Additionally, a phase-only spatial light modulator is able to scan only a sample’s target area by generating a specific discrete line focus according to the shape and location of the target area. Compared with other multiphoton microscopies, this technique shortens scanning time and minimizes photodamage by concentrating scanning energy and dwell time on the area of interest. PMID:22378407

Qin, Wan; Shao, Yonghong; Liu, Honghai; Peng, Xiang; Niu, Hanben; Gao, Bruce

2013-01-01

364

Asymmetries in multiphoton ionization of the ground state of a hydrogen atom  

NASA Astrophysics Data System (ADS)

This paper illustrates the study on asymmetry of the angular distribution of the ejected electrons in a multiphoton process from the ground state of a hydrogen atom. General expressions for the multiphoton ionization rates have been derived based on a variation of the Dalgarno-Lewis method for the evaluation of matrix elements in higher order perturbation theory. In addition, these analytical expressions for the various multiphoton transition rates and their variation as a function of polarization, phase, frequency and intensity of the incident radiation have been studied extensively. The general expression obtained can be used to analyse any number of incident beams with arbitrary polarization, phase and intensity.

Shrestha, Nilam; Radhakrishnan, R.; Babu Thayyullathil, Ramesh

2014-05-01

365

Doppler-free multi-photon excitation : light shift and saturation G. Grynberg  

E-print Network

-photons. Nous montrons que si l'effet Stark dynamique et la saturation sont petits comparés à la largeur Doppler'une quantité égale à l'effet Stark dynamique moyen. Nous consi- dérons également le cas des transitoires, nous, il y a un effet de moyennage par le mouvement : la raie reste Lorentzienne, son centre est déplacé d

Paris-Sud XI, Université de

366

Infrared optical properties of eight different Schott glasses  

NASA Astrophysics Data System (ADS)

The optical properties of glasses are traditionally characterized out to 1 micron in most catalogs, yet, the useful spectral range can extend out to as far as 4 microns. For this reason, the temperature and frequency dependent infrared properties of the Schott glasses Suprasil 300, Ultran 20, SK4, SF6, F2, BK7, UBK7 and KzFSN4 have been measured. This is accomplished by broadband transmittance and reflectance measurements as a function of temperature from room temperature up to 600 degree(s)C. The infrared absorption edge of these glasses is analyzed and modeled with a theoretical multiphoton model and oscillator model. The refractive index of these glasses in the infrared region is estimated from the measurements and a Sellmeier model extending into the infrared is now obtained.

Yang, Di; Thomas, Michael E.; Andersson, Stefan K.; Podgurski, Robert

2000-10-01

367

Excite Assistant  

NSDL National Science Digital Library

Just when the concept of "push" technology seems like yesterday's news, Excite, Inc. produces a handy little program, the Excite Assistant, that pushes data to you without being pushy. The Excite Assistant provides you with instant access to various types of up-to-date information such as the weather for your area, the broadcast TV shows on at the moment, updated stock quotes, your horoscope, and more. The information is summarized within the Assistant's window, but when an item requires expansion, your browser is launched. By far the most useful aspect of this program is the mail notification feature. If you use Excite's Web-based mail service, the Excite Assistant, if active, will play a sound and it's icon will blink when new mail arrives. The Assistant will display the subject line and who the mail is from; clicking on the new mail loads it in your browser. Excite Assistant runs on Win95/98/NT and is free but does display small ads.

368

Single-wavelength reflected confocal and multiphoton microscopy for tissue imaging  

E-print Network

Both reflected confocal and multiphoton microscopy can have clinical diagnostic applications. The successful combination of both modalities in tissue imaging enables unique image contrast to be achieved, especially if a ...

So, Peter T. C.

369

Multiphoton fluorescence recovery after photobleaching : advancements for novel in vivo applications.  

E-print Network

??Multiphoton fluorescence recovery after photobleaching (MP-FRAP) is a laser microscopy technique used to probe the transport properties of macromolecules in biological systems. MP-FRAP utilizes two-photon… (more)

Sullivan, Kelley Diane (1978 - )

2010-01-01

370

Direct Observation of Multiphoton Processes in Laser-Induced Free-Free Transitions  

Microsoft Academic Search

Multiphoton processes are detected in the scattering of electrons on argon atoms in the presence of a strong CO2-laser field. The observations are in accordance with a recently developed semiclassical model.

A. Weingartshofer; J. K. Holmes; G. Caudle; E. M. Clarke; H. Krueger

1977-01-01

371

Multiphoton fluorescence and second harmonic generation microscopy for imaging corneal edema  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate the structural features of corneal edema by multiphoton fluorescence and second harmonic generation (SHG) microscopy and the potential of this technique as a clinical in vivo monitoring technique for cornea disease diagnosis.

Hsueh, Chiu-Mei; Lo, Wen; Tan, Hsin-Yuan; Dong, Chen-Yuan

2008-02-01

372

Wavelength Scaling of High Harmonic Generation Close to the Multiphoton Ionization Regime  

E-print Network

We study the wavelength scaling of high harmonic generation efficiency with visible driver wavelengths in the transition between the tunneling and the multiphoton ionization regimes where the Keldysh parameter is around ...

Lai, Chien-Jen

373

Infrared planar laser-induced fluorescence imaging and applications to imaging of carbon monoxide and carbon dioxide  

NASA Astrophysics Data System (ADS)

This dissertation introduces infrared planar laser- induced fluorescence (IR PLIF) techniques for visualization of species that lack convenient electronic transitions and are therefore unsuitable for more traditional electronic PLIF measurements. IR PLIF measurements can generate high signal levels that scale linearly with both laser energy and species concentration, thereby demonstrating advantages over Raman and multiphoton PLIF techniques. IR PLIF is shown to be a straightforward and effective tool for visualization of CO and CO2 in reactive flows. The slow characteristic times of vibrational relaxation and the large mole fractions of CO and CO2 in typical flows lead to high IR PLIF signal levels, despite the low emission rates typical of vibrational transitions. Analyses of rotational energy transfer (RET) and vibrational energy transfer (VET) show that excitation schemes in either linear (weak) or saturated (strong) limits may be developed, with the fluorescence collected directly from the laser-excited species or indirectly from bath gases in vibrational resonance with the laser-excited species. Use of short (~1 ?s) exposures (for CO) or short exposures combined with long-pulse, high-pulse-energy excitation (for CO2) minimizes unwanted signal variation due to spatially-dependent VET rates. Results are presented for flows ranging from room- temperature mixing to a benchmark CH4 laminar diffusion flame. Linear excitation is appropriate for CO due to its slow vibrational relaxation. However, linear excitation is not well-suited for CO2 imaging due to fast H 2O-enhanced VET processes and the attendant difficulty in interpreting the resulting signal. Saturated excitation using a CO2 laser (or combined CO2 laser-OPO) technique is most appropriate for CO 2, as it generates high signal and minimizes spatial variations in fluorescence quantum yield. Since IR PLIF is applicable to most IR-active species, it has a high potential for expanding the diagnostic possibilities available to combustion researchers. Such diagnostics might include visualization of the fuel region of lifted flames, CO-formation regions in flames, or exhaust mixing processes in internal combustion engines as applied to residual-induced autoignition.

Kirby, Brian James

374

Non-Gaussian features from Excited Squeezed Vacuum State  

E-print Network

In this work, we introduce a non-Gaussian quantum state named excited squeezed vacuum state (ESVS), which can be ustilized to describe quantum light field emitted from the multiphoton quantum process occurred in some restricted quantum systems. We investigate its nonclassical properties such as Wigner distribution in phase space, photon number distribution, the second-order autocorrelation and the quadrature fluctuations. By virtue of the Hilbert-Schmidt distance method, we quantify the non-Gaussianity of the ESVS. Due to the similar photon statistics, we examine the fidelity between the ESVS and the photon-subtraction squeezed vacuum state (PSSVS), and then find the optimal fidelity by monitoring the relevant parameters.

Xubing Tang; Fang Gao; Yaoxiong Wan; Jianguang Wu; Feng Shuang

2014-10-18

375

Spectroscopy of atom and nucleus in a strong laser field: Stark effect and multiphoton resonances  

NASA Astrophysics Data System (ADS)

The consistent relativistic energy approach to atoms in a strong realistic laser field, based on the Gell-Mann and Low S-matrix formalism, is applied in the study of resonant multiphoton ionization of krypton by intense uv laser radiation and for the computation of the resonance shift and width in krypton. The approach to the treatment of the multiphoton resonances in nuclei is outlined for the 57Fe nucleus.

Glushkov, A. V.

2014-11-01

376

Imaging-guided two-photon excitation-emission-matrix measurements of human skin tissues  

NASA Astrophysics Data System (ADS)

There are increased interests on using multiphoton imaging and spectroscopy for skin tissue characterization and diagnosis. However, most studies have been done with just a few excitation wavelengths. Our objective is to perform a systematic study of the two-photon fluorescence (TPF) properties of skin fluorophores, normal skin, and diseased skin tissues. A nonlinear excitation-emission-matrix (EEM) spectroscopy system with multiphoton imaging guidance was constructed. A tunable femtosecond laser was used to vary excitation wavelengths from 730 to 920 nm for EEM data acquisition. EEM measurements were performed on excised fresh normal skin tissues, seborrheic keratosis tissue samples, and skin fluorophores including: NADH, FAD, keratin, melanin, collagen, and elastin. We found that in the stratum corneum and upper epidermis of normal skin, the cells have large sizes and the TPF originates from keratin. In the lower epidermis, cells are smaller and TPF is dominated by NADH contributions. In the dermis, TPF is dominated by elastin components. The depth resolved EEM measurements also demonstrated that keratin structure has intruded into the middle sublayers of the epidermal part of the seborrheic keratosis lesion. These results suggest that the imaging guided TPF EEM spectroscopy provides useful information for the development of multiphoton clinical devices for skin disease diagnosis.

Yu, Yingqiu; Lee, Anthony M. D.; Wang, Hequn; Tang, Shuo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

2012-07-01

377

Theory of multiphoton and tunnel ionization in a bichromatic field  

SciTech Connect

The imaginary-time method [6, 7] is used to calculate the multiphoton and tunnel ionization probabilities for atoms in a laser radiation field part of which is converted into the second harmonic. We assume that the first harmonic has a linear or elliptical polarization and the second harmonic is polarized linearly, with its polarization vector making an arbitrary angle with that of the first harmonic. The mean momentum of the photoelectrons knocked out from atoms is shown to depend on the phase shift between the first and second harmonics and their mutual polarization and to be identically equal to zero for a monochromatic field. An important difference between the case of elliptical polarization and the case of linear polarization of both harmonics is the absence of conditions under which the conditions for dominance of one of the two generation mechanisms considered here can be identified during the generation of terahertz radiation from the region of optical breakdown in a gas.

Bagulov, D. S., E-mail: bagulov-denis@yandex.ru [Novosibirsk State University (Russian Federation); Kotelnikov, I. A., E-mail: I.A.Kotelnikov@inp.nsk.ru [Russian Academy of Sciences, Siberian Branch, Budger Institute of Nuclear Physics (Russian Federation)

2013-01-15

378

Clinical multiphoton tomography and clinical two-photon microendoscopy  

NASA Astrophysics Data System (ADS)

We report on applications of high-resolution clinical multiphoton tomography based on the femtosecond laser system DermaInspectTM with its flexible mirror arm in Australia, Asia, and Europe. Applications include early detection of melanoma, in situ tracing of pharmacological and cosmetical compounds including ZnO nanoparticles in the epidermis and upper dermis, the determination of the skin aging index SAAID as well as the study of the effects of anti-aging products. In addition, first clinical studies with novel rigid high-NA two-photon 1.6 mm GRIN microendoscopes have been conducted to study the effect of wound healing in chronic wounds (ulcus ulcera) as well as to perform intrabody imaging with subcellular resolution in small animals.

König, Karsten; Bückle, Rainer; Weinigel, Martin; Elsner, Peter; Kaatz, Martin

2009-02-01

379

Tunneling dynamics in multiphoton ionization and attoclock calibration  

E-print Network

The intermediate domain of strong-field ionization between the tunneling and the multiphoton regimes is investigated using the strong field approximation and the imaginary-time method. An intuitive model for the dynamics is developed which describes the ionization process within a nonadiabatic tunneling picture with a coordinate dependent electron energy during the under-the-barrier motion. The nonadiabatic effects in the elliptically polarized laser field induce a transversal momentum shift of the tunneled electron wave packet at the tunnel exit, a delayed appearance in the continuum as well as a shift of the tunneling exit towards the ionic core. The latter significantly modifies the Coulomb focusing during the electron excursion in the laser field after exiting the ionization tunnel. We show that nonadiabatic effects are especially large when the Coulomb field of the ionic core is taken into account during the under-the-barrier motion. The simpleman model modified with these nonadiabatic corrections provid...

Klaiber, M; Keitel, C H

2014-01-01

380

Multiphoton intravital microscopy setup to visualize the mouse mammary gland  

NASA Astrophysics Data System (ADS)

Recently, light microscopy-based techniques have been extended to live mammalian models leading to the development of a new imaging approach called intravital microscopy (IVM). Although IVM has been introduced at the beginning of the last century, its major advancements have occurred in the last twenty years with the development of non-linear microscopy that has enabled performing deep tissue imaging. IVM has been utilized to address many biological questions in basic research and is now a fundamental tool that provide information on tissues such as morphology, cellular architecture, and metabolic status. IVM has become an indispensable tool in numerous areas. This study presents and describes the practical aspects of IVM necessary to visualize epithelial cells of live mouse mammary gland with multiphoton techniques.

Adur, Javier; Herrera Torres, Ana M.; Masedunskas, Andrius; Baratti, Mariana O.; de Thomaz, Andre A.; Pelegati, Vitor B.; Carvalho, Hernandes F.; Cesar, Carlos L.

2013-06-01

381

Multiphoton Coherent Manipulation in Large-Spin Qubits  

NASA Astrophysics Data System (ADS)

Large-spin Mn2+ ions (S=5/2) diluted in a nonmagnetic MgO matrix of high crystalline symmetry are used to realize a six-level system that can be operated by means of multiphoton coherent Rabi oscillations. This spin system has a very small anisotropy which can be tuned in situ to reversibly transform the system between harmonic and nonharmonic level configurations. Decoherence effects are strongly suppressed as a result of the quasi-isotropic electron interaction with the crystal field and with the Mn55 nuclear spins. These results suggest new ways of manipulating, reading, and resetting spin quantum states which can be applied to encode a qubit across several quantum levels.

Bertaina, S.; Chen, L.; Groll, N.; van Tol, J.; Dalal, N. S.; Chiorescu, I.

2009-02-01

382

Multiphoton gradient index endoscopy for evaluation of diseased human prostatic tissue ex vivo  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy can instantly visualize cellular details in unstained tissues. Multiphoton probes with clinical potential have been developed. This study evaluates the suitability of multiphoton gradient index (GRIN) endoscopy as a diagnostic tool for prostatic tissue. A portable and compact multiphoton endoscope based on a 1-mm diameter, 8-cm length GRIN lens system probe was used. Fresh ex vivo samples were obtained from 14 radical prostatectomy patients and benign and malignant areas were imaged and correlated with subsequent H&E sections. Multiphoton GRIN endoscopy images of unfixed and unprocessed prostate tissue at a subcellular resolution are presented. We note several differences and identifying features of benign versus low-grade versus high-grade tumors and are able to identify periprostatic tissues such as adipocytes, periprostatic nerves, and blood vessels. Multiphoton GRIN endoscopy can be used to identify both benign and malignant lesions in ex vivo human prostate tissue and may be a valuable diagnostic tool for real-time visualization of suspicious areas of the prostate.

Huland, David M.; Jain, Manu; Ouzounov, Dimitre G.; Robinson, Brian D.; Harya, Diana S.; Shevchuk, Maria M.; Singhal, Paras; Xu, Chris; Tewari, Ashutosh K.

2014-11-01

383

Multiphoton fluorescence microscopy of the live kidney in health and disease.  

PubMed

The structural and functional heterogeneity of the kidney ensures a diversity of response in health and disease. Multiphoton microscopy has improved our understanding of kidney physiology and pathophysiology by enabling the visualization of the living kidney in comparison with the static view of previous technologies. The use of multiphoton microscopy with rodent models in conjunction with endogenous fluorescence and exogenous infused dyes permits the measurement of renal processes, such as glomerular permeability, juxtaglomerular apparatus function, tubulointerstitial function, tubulovascular interactions, vascular flow rate, and the intrarenal renin-angiotensin-aldosterone system. Subcellular processes, including mitochondrial dynamics, reactive oxygen species production, cytosolic ion concentrations, and death processes apoptosis and necrosis, can also be measured by multiphoton microscopy. This has allowed valuable insight into the pathophysiology of diabetic nephropathy, renal ischemia-reperfusion injury, hypertensive nephropathy, as well as inflammatory responses of the kidney. The current review presents an overview of multiphoton microscopy with a focus on techniques for imaging the kidney and gives examples of instances where multiphoton microscopy has been utilized to study renal pathophysiology in the living kidney. With continued advancements in the field of biological optics and increased adoption in experimental nephrology, multiphoton microscopy will undoubtedly continue to create new paradigms in kidney disease. PMID:24525825

Small, David M; Sanchez, Washington Y; Roy, Sandrine; Hickey, Michael J; Gobe, Glenda C

2014-02-01

384

Evaluating thermal damage induced by pulsed light with multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Nonablative skin remodeling is a new light treatment approach for photodamaged skin. Compared to ablative CO2 or Er:YAG laser resurfacing, dermabrasion, and chemical peels, the clinical objective of nonablative skin remodeling is to maximize thermal damage to upper dermis while minimizing injury to the epidermis and surrounding tissue, consequently decreasing potential complications and shortening long recuperation periods. Histological analysis of preoperative and postoperative biopsies using H&E or special stains has indicated the dermal thermal injury, which resulting in collagen denaturation, is the most important mechanism of nonablative skin remodeling for improving skin situation. And the extent of improvement of skin situation corresponded to the formation of a new band of dense, compact collagen bundles in the papillary dermis. The diversity of individual skin condition influences the choice of pulsed light treatment parameters, and further influences the degree of dermal thermal damage, thus the efficacy of nonablative skin remodeling remains unstable. Recently, multiphoton microscopy has show a promising application for monitoring skin thermal damage, because collagen could produce strong second harmonic generation (SHG). And SHG intensity is presumably proportional to the percentage of collagen in dermis. In this paper, the auto-fluorescence (AF) intensity and SHG intensity of mice skin irradiated by pulsed Nd:YAG laser were measured and imaged with multiphoton microscope, and the results show the ratio of SHG to AF decreases with the increase of irradiation exposure dose, and could be a quantitative technique to assess dermal thermal damage, and could further benefit the choice of light treatment parameters.

Gong, Wei; Xie, Shusen; Huang, Yimei

2009-02-01

385

Advances in polarization sensitive multiphoton nano-bio-imaging  

NASA Astrophysics Data System (ADS)

In this talk, we shall shortly review four main directions of ongoing research in our laboratories, directed at the conception and demonstration of a variety of innovative configurations in nanoscale multiphoton imaging. A common feature to all of these directions appears to be the central role played by the involvement of polarization features, both in- and outgoing, moreover so in view of the tensorial aspects inherent to nonlinear schemes such second-harmonic generation, electro-optic modulation or two-photon fluorescence which will ne emphasized. These advances relate to the new domain of nonlinear ellipsometry in multiphoton imaging [1], of high relevance to fundamental aspects of nanophotonics and nanomaterial engineering as well as towards basic life science issues. The four domains to be shortly reported are: a) polarization resolved second-harmonic generation in semiconductor QD’s with record small sizes in the 10-12 nm range [2] b) original use of two-photon confocal polarization resolved microscopy in DNA stained by two photon fluorescent dyes in different LC phases arrangements so as to characterize these as well as ascertain the respective DNA-dye orientation (intercalant or groves) [3] c) elaboration and demonstration of an electrooptic confocal microscope in a highly sensitive interferometric and homodyne detection configuration allowing to map weak electric potentials such as in artificial functionalized membranes, the dynamical investigation of firing and propagation aspects of action potentials in neurones being currently the next step [4] d) original plasmon based enhanced nanoscale confocal imaging involving a dual detection scheme (fluorescence imaging and ATR plasmon coupling in reflection) whereby adequate preparation and switching of the incoming polarization state between radial, linear and azimuthal configurations, entail different images and plasmon enhancement levels [5].

Chauvat, D.; Hajj, B.; Mojzisova, H.; Oron, D.; Sung, H.; Winter, S.; Zielinski, M.; Zyss, J.

2010-06-01

386

Mid-infrared soliton and Raman frequency comb generation in silicon microrings.  

PubMed

We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cw-pumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described. PMID:25490668

Hansson, Tobias; Modotto, Daniele; Wabnitz, Stefan

2014-12-01

387

Mid-infrared soliton and Raman frequency comb generation in silicon microrings  

NASA Astrophysics Data System (ADS)

We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cw pumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free-carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described.

Hansson, Tobias; Modotto, Daniele; Wabnitz, Stefan

2014-12-01

388

Nonadiabatic approach for resonant molecular multiphoton absorption processes in intense infrared laser fields  

E-print Network

, including state?to?state multiquantum transitions and transitions from initially thermally distributed states as a whole. Results are presented for the case of IR laser intensity 50 GW/cm2 and frequencies ranging from 2115 to 2165 cm? 1. Excellent agreement...

Ho, Tak-San; Chu, Shih-I

1983-07-14

389

Excited Insects  

E-print Network

but not killing them doesn't actually count as true celebration. Now, China. There's a country that knows how to make a bug feel good. Bugs have their very own holiday in the Chinese calendar. It's called the Feast of the Excited Insects and it falls on March 5th...

Hacker, Randi

2011-04-06

390

Intramolecular vibrational dynamics in bis(trifluoromethyl)keten excited by resonant femtosecond IR radiation  

NASA Astrophysics Data System (ADS)

Vibrational dynamics in different modes of (CF3)2CCO molecule induced by resonant femtosecond IR excitation of the ?1 mode is studied. Selective multiphoton excitation of this mode is observed up to the level v = 7. Intramolecular vibrational redistribution (IVR) causes relaxation of the ?1 mode with a time constant ?IVR = 5 ps. The 'instantaneous' (? ? ?IVR) transient absorbance ?OD signal at nonresonant modes ?2, ?3, and ?4 is revealed. Subsequent evolution of the ?OD signal and the corresponding time constants are different for different modes, which we associate with different migration pathways of the vibrational energy.

Chekalin, S. V.; Kompanets, V. O.; Laptev, V. B.; Pigul'sky, S. V.; Makarov, A. A.; Ryabov, E. A.

2011-08-01

391

Formation of vibrationally excited methyl radicals following state-specific excitation of methylamine.  

PubMed

The photochemistry of methylamine has been investigated following state-specific excitation of the S1 state. 2 + 1 resonance-enhanced multiphoton ionization was used to detect nascent methyl radical products via the 3p(2)A2?-X?(2)A2? electronic transition. Methyl radicals were formed at all photolysis wavelengths used over the range of 222-240 nm. The nascent products showed significant rotational excitation and several quanta of vibrational excitation in ?3, the degenerate C-H stretch. The partially deuterated methyl-d3-amine isotopologue yielded methyl-d3 fragments with vibrational distributions entirely consistent with those measured for the fully protiated species; no mixed isotopologues were detected. Energetic constraints require that the vibrationally excited methyl radicals be produced in conjunction with electronic ground-state NH2 X?(2)B1 radicals on the S0 surface, negating the previous interpretation that dissociation occurs on the upper adiabat. New ab initio calculations characterizing the C-N bond cleavage coordinate confirm the presence of a barrier to dissociation on S1 that is insurmountable at the photolysis wavelengths used in this work. We propose a "semi-direct" mechanism in which frustrated aminyl H atom loss on the upper adiabatic potential energy surface leads to internal conversion at the exit channel conical intersection at an extended N-H distance on its return. It is proposed that C-N bond cleavage then occurs promptly and nonstatistically on the S0 surface. PMID:25250899

Thomas, James O; Lower, Katherine E; Murray, Craig

2014-10-23

392

Simultaneous two-photon excitation of photodynamic therapy agents  

SciTech Connect

The spectroscopic and photochemical properties of several photosensitive compounds are compared using conventional single-photon excitation (SPE) and simultaneous two-photon excitation (TPE). TPE is achieved using a mode-locked titanium:sapphire laser, the near infrared output of which allows direct promotion of non-resonant TPE. Excitation spectra and excited state properties of both type 1 and type 2 photodynamic therapy (PDT) agents are examined.

Wachter, E.A.; Fisher, W.G. [Oak Ridge National Lab., TN (United States)]|[Photogen, Inc., Knoxville, TN (United States); Partridge, W.P. [Oak Ridge National Lab., TN (United States); Dees, H.C. [Photogen, Inc., Knoxville, TN (United States); Petersen, M.G. [Univ. of Tennessee, Knoxville, TN (United States). College of Veterinary Medicine

1998-01-01

393

Infrared Gallery  

NSDL National Science Digital Library

Human eyes cannot see infrared wavelengths, but with the help of false-color imaging, temperature differences become visible and invisible features are suddenly illuminated. This interactive gallery shows images of a variety of objects and geothermal features in both visible and infrared light, and explains why the infrared images show the items as they do. A background essay and list of discussion questions are also provided.

394

Structure of multiphoton quantum optics. I. Canonical formalism and homodyne squeezed states  

NASA Astrophysics Data System (ADS)

We introduce a formalism of nonlinear canonical transformations for general systems of multiphoton quantum optics. For single-mode systems the transformations depend on a tunable free parameter, the homodyne local-oscillator angle; for n -mode systems they depend on n heterodyne mixing angles. The canonical formalism realizes nontrivial mixing of pairs of conjugate quadratures of the electromagnetic field in terms of homodyne variables for single-mode systems, and in terms of heterodyne variables for multimode systems. In the first instance the transformations yield nonquadratic model Hamiltonians of degenerate multiphoton processes and define a class of non-Gaussian, nonclassical multiphoton states that exhibit properties of coherence and squeezing. We show that such homodyne multiphoton squeezed states are generated by unitary operators with a nonlinear time evolution that realizes the homodyne mixing of a pair of conjugate quadratures. Tuning of the local-oscillator angle allows us to vary at will the statistical properties of such states. We discuss the relevance of the formalism for the study of degenerate (up-)down-conversion processes. In a companion paper [

F. Dell’Anno, S. De Siena, and F. Illuminati, 69, 033813 (2004)
], we provide the extension of the nonlinear canonical formalism to multimode systems, we introduce the associated heterodyne multiphoton squeezed states, and we discuss their possible experimental realization.

dell'Anno, Fabio; de Siena, Silvio; Illuminati, Fabrizio

2004-03-01

395

Structure of multiphoton quantum optics. I. Canonical formalism and homodyne squeezed states  

SciTech Connect

We introduce a formalism of nonlinear canonical transformations for general systems of multiphoton quantum optics. For single-mode systems the transformations depend on a tunable free parameter, the homodyne local-oscillator angle; for n-mode systems they depend on n heterodyne mixing angles. The canonical formalism realizes nontrivial mixing of pairs of conjugate quadratures of the electromagnetic field in terms of homodyne variables for single-mode systems, and in terms of heterodyne variables for multimode systems. In the first instance the transformations yield nonquadratic model Hamiltonians of degenerate multiphoton processes and define a class of non-Gaussian, nonclassical multiphoton states that exhibit properties of coherence and squeezing. We show that such homodyne multiphoton squeezed states are generated by unitary operators with a nonlinear time evolution that realizes the homodyne mixing of a pair of conjugate quadratures. Tuning of the local-oscillator angle allows us to vary at will the statistical properties of such states. We discuss the relevance of the formalism for the study of degenerate (up-)down-conversion processes. In a companion paper [F. Dell'Anno, S. De Siena, and F. Illuminati, 69, 033813 (2004)], we provide the extension of the nonlinear canonical formalism to multimode systems, we introduce the associated heterodyne multiphoton squeezed states, and we discuss their possible experimental realization.

Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio [Dipartimento di Fisica 'E. R. Caianiello', Universita di Salerno, INFM UdR di Salerno, INFN Sezione di Napoli, Gruppo Collegato di Salerno, Via S. Allende, 84081 Baronissi, SA (Italy)

2004-03-01

396

Multiphoton (e, 2e) process of hydrogen atom in strong laser field  

NASA Astrophysics Data System (ADS)

The dynamics of the electron impact multiphoton ionization of a hydrogen atom in the presence of an intense laser field (e, n ? e) has been studied theoretically for laser polarization parallel (\\vert \\vertl) and perpendicular (?r) to the incident momentum, with a view to comparing (qualitatively) the results with the recent kinematically complete experiments of Höhr et al. [Phys. Rev. Lett. 94, 153201 (2005)] for the He target. Significant laser modifications are noted in the present doubly (DDCS) and the fully differential multiphoton cross sections (TDCS) for both the geometries (\\vert \\vertl and ?r). For most of the explored kinematics (chosen in accordance with the experiment), the present binary peak intensity of the laser-assisted multiphoton TDCS is significantly enhanced with respect to the field free ones, in qualitative agreement with the experiment. Importance of the multiphoton effects is also studied. The multiphoton cross sections in the zeroth order approximation of the ejected electron wavefunction (CV) obeys the Kroll Watson sum rule while it does not hold good in the corresponding first order approximation (MCV).

Ghosh Deb, S.; Roy, S.; Sinha, C.

2009-12-01

397

Sub-Doppler tunable far-infrared spectroscopy  

Microsoft Academic Search

The first experimental observations of sub-Doppler linewidths in a cell made using tunable far-infrared radiation are reported. A double-resonance scheme has been used, combining CO2-laser infrared radiation with tunable far-infrared radiation to observe a sub-Doppler line shape in an excited vibrational state of CH3OH.

M. Inguscio; L. R. Zink; K. M. Evenson; D. A. Jennings

1987-01-01

398

Rapid creation of distant entanglement by multiphoton resonant fluorescence  

NASA Astrophysics Data System (ADS)

We study a simple, effective, and robust method for entangling two separate stationary quantum dot spin qubits with high fidelity using multiphoton Gaussian state. The fluorescence signals from the two dots interfere at a beam splitter. The bosonic nature of photons leads, in analogy with the Hong-Ou-Mandel effect, to selective pairing of photon holes (photon absences in the fluorescent signals). As a result, two odd photon number detections at the outgoing beams herald trion entanglement creation, and subsequent reduction of the trions to the spin ground states leads to spin-spin entanglement. The robustness of the Gaussian states is evidenced by the ability to compensate for photon absorption and noise by a moderate increase in the number of photons at the input. We calculate the entanglement generation rate in the ideal, nonideal, and near-ideal detector regimes and find substantial improvement over single-photon schemes in all three regimes. Fast and efficient spin-spin entanglement creation can form the basis for a scalable quantum dot quantum computing network. Our predictions can be tested using current experimental capabilities.

Cohen, Guy Z.; Sham, L. J.

2013-12-01

399

The analysis of aging skin based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Aging is a very important issue not only in dermatology, but also in cosmetic science. Cutaneous aging involves both chronological and photoaging aging process. The chronological aging is induced with the passage of time. And the photoaging skin is the extrinsic aging caused by sun exposure. The aim of this study is to use multiphoton microscopy (MPM) in vivo to assess intrinsic-age-related and photo-age-related difference. The changes of dermal collagen are measured in quantitively. The algorithm that we used automatically produced the transversal dermal map from MPM. Others, the texture of dermis are analyzed by Fourier transform and Gray Level Co-occurrence Matrix. And the object extraction in textured images is proposed based on the method in object edge extraction, and the aim of it is to detect the object hidden in the skin texture in difference aging skin. The result demonstrates that the approach is effective in detecting the object in epidermis and dermis textured image in different aging skin. It could help to further understand the aging mechanism.

Wu, Shulian; Li, Hui; Zhang, Xiaoman; Li, Zhifang; Xu, Shufei

2010-11-01

400

Multiphoton absorption in polydiacetylenes adsorbed on metal nanostructures  

NASA Astrophysics Data System (ADS)

We report on the measurement of the multi-photon absorption dispersion of polydiacetylene-decorated silver nanoparticles in water solution. They were prepared by self assembly of the monomer 10,12-pentacosadiynoic acid (PCDA) onto pre-formed chitosan-stabilized Ag nanoparticles (Chit-AgNps) followed by photopolymerization of the diacetylenic outer shell. Z-Scan technique with fs pulses in open aperture configuration was employed: the spectral range covered the region between 1150 and 1350 nm. We tentatively attribute our results to a two photon state (2Ag) which peaks at 600 nm. This result is consistent with the fluorescence spectrum that shows an emitting state lying at about 650 nm, in addition to a peak at 568 nm which is attributed to the emission of an orange form of the polymer. However we cannot rule out the possibility that we are also dealing with higher order absorption processes and further studies are needed to clarify this point and to provide a deeper insight into the origin of the emission spectrum.

Pilot, R.; Bozio, R.; Demartini, A.; Alloisio, M.; Dellepiane, G.; Giorgetti, E.

2010-05-01

401

Tunneling dynamics in multiphoton ionization and attoclock calibration  

E-print Network

The intermediate domain of strong-field ionization between the tunneling and the multiphoton regimes is investigated using the strong field approximation and the imaginary-time method. An intuitive model for the dynamics is developed which describes the ionization process within a nonadiabatic tunneling picture with a coordinate dependent electron energy during the under-the-barrier motion. The nonadiabatic effects in the elliptically polarized laser field induce a transversal momentum shift of the tunneled electron wave packet at the tunnel exit, a delayed appearance in the continuum as well as a shift of the tunneling exit towards the ionic core. The latter significantly modifies the Coulomb focusing during the electron excursion in the laser field after exiting the ionization tunnel. We show that nonadiabatic effects are especially large when the Coulomb field of the ionic core is taken into account during the under-the-barrier motion. The simpleman model modified with these nonadiabatic corrections provides an intuitive background for exact theories and has direct implications for the calibration of the attoclock technique which is used for the measurement of the tunneling delay time.

M. Klaiber; K. Z. Hatsagortsyan; C. H. Keitel

2014-08-25

402

Multiphoton gonioscopy to image the trabecular meshwork of porcine eyes  

NASA Astrophysics Data System (ADS)

The aqueous outflow system (AOS), including the trabecular meshwork (TM), the collector channels (CC) and the Schlemm's canal (SC), regulates intraocular pressure (IOP) through the drainage of the aqueous humor (AH). Abnormal IOP elevation leads to increased pressure stress to retinal ganglion cells, resulting in cell loss that can ultimately lead to complete loss of eyesight. Therefore, development of imaging tools to detect abnormal structural and functional changes of the AOS is important in early diagnosis and prevention of glaucoma. Multiphoton microscopy (MPM), including twophoton autofluorescence (TPAF) and second harmonic generation (SHG), is a label-free microscopic technique that allows molecular specific imaging of biological tissues like the TM. Since the TM and other AOS structures are located behind the highly scattering scleral tissue, transscleral imaging of the TM does not provide enough optical resolution. In this work, a gonioscopic lens is used to allow direct optical access of the TM through the cornea for MPM imaging. Compared to transscleral imaging, the acquired MPM images show improved resolution as individual collagen fiber bundles of the TM can be observed. MPM gonioscopy may have the potential to be developed as a future clinical imaging tool for glaucoma diagnostics.

Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Gibson, Emily A.; Lei, Tim C.

2013-03-01

403

Multiphoton, confocal, and lifetime microscopy for molecular imaging in cartilage  

NASA Astrophysics Data System (ADS)

It has recently been shown that mutations in Filamin A and B genes produce a large spectrum of skeletal disorders in developing fetuses. However, high-resolution optical microscopy in cartilage growth plate using fluorescent antibody assays, which should elucidate molecular aspects of these disorders, is extremely difficult due to the high level of autofluoresce in this tissue. We apply multiphoton, confocal, lifetime and spectral microscopy to (i) image and characterize autofluorophores in chondrocytes and subtract their contributions to obtain a corrected antibody-marker fluorescence signal, and (ii) measure the interaction between Filamin A and B proteins by detecting the fluorescence resonance energy transfer (FRET) between markers of the two proteins. Taking advantage of the different fluorescence spectra of the endogenous and exogenous markers, we can significantly reduce the autofluorescence background. Preliminary results of the FRET experiments suggest no interaction between Filamin A and B proteins. However, developing of new antibodies targeting the carboxy-terminal immunoglobulin-like domain may be necessary to confirm this result.

Wachsmann-Hogiu, Sebastian; Krakow, Deborah; Kirilova, Veneta T.; Cohn, Daniel H.; Bertolotto, Cristina; Acuna, Dora; Fang, Qiyin; Krivorov, Nikola; Farkas, Daniel L.

2005-03-01

404

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Results and prospects of laser separation of oxygen isotopes by IR multiphoton dissociation of molecules  

NASA Astrophysics Data System (ADS)

An experimental search was made for an initial oxygen compound suitable for laser separation of oxygen isotopes by IR multiphoton dissociation of molecules. Over ten molecules with C—O, Si—O, Cr=O, and C=O bonds were investigated. The excitation was provided by pulsed TEA CO2 laser radiation, and also by its second harmonic. Measurements were made of the dissociation yields of the molecular components containing 18O and 16O and of the isotopic selectivity as a function of the frequency and fluence of laser radiation, pressure of the gas being dissociated, etc. The suitability of the investigated compounds for practical laser separation of oxygen isotopes was analysed.

Laptev, Vladimir B.; Ryabov, Evgenii A.; Tumanova, L. M.

1995-06-01

405

Tri-modal microscopy with multiphoton and optical coherence microscopy/tomography for multi-scale and multi-contrast imaging.  

PubMed

Multi-scale multimodal microscopy is a very useful technique by providing multiple imaging contrasts with adjustable field of views and spatial resolutions. Here, we present a tri-modal microscope combining multiphoton microscopy (MPM), optical coherence microscopy (OCM) and optical coherence tomography (OCT) for subsurface visualization of biological tissues. The advantages of the tri-modal system are demonstrated on various biological samples. It enables the visualization of multiple intrinsic contrasts including scattering, two-photon excitation fluorescence (TPEF), and second harmonic generation (SHG). It also enables a rapid scanning over a large tissue area and a high resolution zoom-in for cellular-level structures on regions of interest. The tri-modal microscope can be important for label-free imaging to obtain a sufficient set of parameters for reliable sample analysis. PMID:24049679

Chong, Shau Poh; Lai, Tom; Zhou, Yifeng; Tang, Shuo

2013-01-01

406

Label-free multiphoton imaging and photoablation of preinvasive cancer cells  

NASA Astrophysics Data System (ADS)

Detection and treatment of early lesions in epithelial tissue offer several possibilities for curing cancer, but it is challenging. Here, we present an optical technique, the combination of multiphoton imaging and absorption, to label-freely detect and ablate preinvasive cancer cells in epithelial tissue. We find that multiphoton imaging can label-freely visualize the principal features of nuclear atypia associated with epithelial precancerous lesions, and the spatial localization of multiphoton absorption can perform targeted ablation of preinvasive cancer cells with micrometer-sized volume precision. These results indicate that this optical technique has the capability to label-freely visualize and remove preinvasive cancer cells in epithelial tissue. This study highlights the potential of this technique as a "seek-and-treat" tool for early lesions in epithelial tissue.

Zhuo, Shuangmu; Chen, Jianxin; Wu, Guizhu; Zhu, Xiaoqin; Jiang, Xingshan; Xie, Shusen

2012-01-01

407

Two-photon imaging of intact living plants during freezing with a flexible multiphoton tomograph  

NASA Astrophysics Data System (ADS)

We describe the combination of a flexible multiphoton tomograph (MPTflex) with a heating and cooling stage. The stage allows temperature control in the range of (?196?°C) (77?K) to +600?°C (873?K) with selectable heating/freezing rates between 0.01?K?min?1 and 150?K?min?1. To illustrate the imaging capabilities of the combined system, fluorescence intensity and lifetime of intrinsic molecules from a plant leaf were imaged with submicron resolution during freezing in vivo without detaching the leaf from the plant. An increase of fluorescence intensity and decay times with decreasing temperature was observed. The measurements illustrate the usefulness of multiphoton imaging as a non-invasive online tool to investigate temperature-induced effects. The flexible multiphoton tomograph with its adjustable mechano-optical arm and scan head allows imaging at otherwise hardly accessible sample regions.

Breunig, H. G.; König, K.

2015-02-01

408

Multiphoton processes in the field of two-frequency circularly polarized plane electromagnetic waves  

SciTech Connect

The authors solve Dirac`s equation for an electron in the field of a two-frequency plane electromagnetic wave, deriving general formulae for the probabilities of radiation of a photon by the electron, and for the probabilities for pair production by a photon when the two-frequency wave is circularly polarized. In contrast to the case of a monochromatic-plane electromagnetic wave, when an electron is in the field of a two-frequency circularly polarized wave, besides the absorption of multiphotons and emission of simple harmonics of the individual waves, stimulated multiphoton emission processes and various composite harmonic-photon emission processes are occurred: when a high-energy photon is in a such a field, multiphoton processes also follow the pair production processes.

Yu, An [Brookhaven National Lab., Upton, NY (United States)]|[Tsinghua Univ., Beijing (China). Physics Dept.; Takahashi, H. [Brookhaven National Lab., Upton, NY (United States)

1997-07-01

409

Resonance-enhanced multiphoton ionization time-of-flight mass spectrometry for detection of nitrogen containing aliphatic and aromatic compounds: resonance-enhanced multiphoton ionization spectroscopic investigation and on-line analytical application.  

PubMed

Resonance-enhanced multiphoton ionization (REMPI) combined with time-of-flight mass spectrometry (TOFMS) is an analytical method capable of on-line monitoring of trace compounds in complex matrices. A necessary prerequisite for substance selective detection is spectroscopic investigation of the target molecules. Several organic nitrogen compounds comprising aliphatic and aromatic amines, nitrogen heterocyclic compounds, and aromatic nitriles are spectroscopically investigated with a tunable narrow bandwidth optical parametric oscillator (OPO) laser system providing a scannable wavelength range between 220 and 340 nm. These species are known as possible precursors in fuel-NO formation from combustion of solid fuels such as biomass and waste. A newly conceived double inlet system was used in this study, which allows rapid change between effusive and supersonic molecular beams. The resulting REMPI spectra of the compounds are discussed with respect to electronic transitions that could be utilized for a selective ionization of these compounds in complex mixtures such as combustion and process gases. The practicability of this approach is demonstrated by wavelength selected on-line REMPI-TOFMS detection of aniline and cyanonaphthalene in the burning chamber of a waste incineration plant. REMPI mass spectra recorded at different excitation wavelengths as well as variations in time show the utilization of species-selective REMPI-TOFMS detection for on-line monitoring of crucial substances in pollutant formation. PMID:16454915

Streibel, T; Hafner, K; Mühlberger, F; Adam, T; Zimmermann, R

2006-01-01

410

A model for multiphoton absorption in dielectric materials induced by short laser pulses at moderate intensities  

NASA Astrophysics Data System (ADS)

We present a semi-analytical model for free electron production induced by multiphoton ionization in dielectric materials for short laser pulses at moderate intensities. Within this approach, the laser-induced absorption is described through the Bloch-Volkov formalism, and the electronic structure of materials is evaluated through first-principles calculations. Results obtained for NaCl and KDP (KH2PO4) materials show that significant deviations from the parabolic band approximation may occur. When the laser intensity increases, high multiphotonic orders may become the predominant mechanisms outside the centre of the Brillouin zone.

Mézel, Candice; Duchateau, Guillaume; Geneste, Grégory; Siberchicot, Bruno

2013-06-01

411

Diagrammatic analysis of multiphoton processes in a ladder-type three-level atomic system  

SciTech Connect

We present a diagrammatic method for complete characterization of multiphoton processes in three-level atomic systems. By considering the interaction routes of the coupling and probe photons for a ladder-type, three-level, noncycling (or cycling) atomic system, we are able to completely discriminate between the pure one-photon and the pure two-photon resonance effects, and the effect of their combination in electromagnetically induced transparency (EIT) using our diagrammatic method. We show that the proposed diagrammatic method is very useful for the analysis of multiphoton processes in ladder-type EIT.

Noh, Heung-Ryoul [Department of Physics, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Moon, Han Seb [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of)

2011-11-15

412

Label-free diagnosis of human hepatocellular carcinoma by multiphoton autofluorescence microscopy  

NASA Astrophysics Data System (ADS)

Conventional diagnosis for hepatocellular carcinoma (HCC) is time consuming in sample preparation and deficient in quantitative examination. In this work, we developed multiphoton autofluorescence (MAF) microscopy as an effective and efficient tool in HCC diagnosis with qualitative imaging and quantitative measurement. We found that MAF imaging effectively identifies cellular architecture in the liver specimens. Our results also demonstrate the capability of using tissue quantitative parameters of multiphoton autofluorescence intensity ratio, the nuclear number density, and nuclear-cytoplasmic ratio for tumor discrimination. This approach has the potential in clinical diagnosis of HCC and the in vivo investigation of liver tumor development in animal models.

Sun, Tzu-Lin; Liu, Yuan; Sung, Ming-Chin; Chen, Hsiao-Ching; Yang, Chun-Hui; Hovhannisyan, Vladimir; Lin, Wei-Chou; Chen, Wei-Liang; Chiou, Ling-Ling; Huang, Guan-Tarn; Kim, Ki Hean; So, Peter T. C.; Lee, Hsuan-Shu; Dong, Chen-Yuan

2009-11-01

413

Kinetic modeling of evolution of 3?+?1:Resonance enhanced multiphoton ionization plasma in argon at low pressures  

SciTech Connect

We present numerical kinetic modeling of generation and evolution of the plasma produced as a result of resonance enhanced multiphoton ionization (REMPI) in Argon gas. The particle-in-cell/Monte Carlo collision (PIC/MCC) simulations capture non-equilibrium effects in REMPI plasma expansion by considering the major collisional processes at the microscopic level: elastic scattering, electron impact ionization, ion charge exchange, and recombination and quenching for metastable excited atoms. The conditions in one-dimensional (1D) and two-dimensional (2D) formulations correspond to known experiments in Argon at a pressure of 5?Torr. The 1D PIC/MCC calculations are compared with the published results of local drift-diffusion model, obtained for the same conditions. It is shown that the PIC/MCC and diffusion-drift models are in qualitative and in reasonable quantitative agreement during the ambipolar expansion stage, whereas significant non-equilibrium exists during the first few 10?s of nanoseconds. 2D effects are important in the REMPI plasma expansion. The 2D PIC/MCC calculations produce significantly lower peak electron densities as compared to 1D and show a better agreement with experimentally measured microwave radiation scattering.

Tholeti, Siva Sashank; Alexeenko, Alina A., E-mail: alexeenk@purdue.edu [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States); Shneider, Mikhail N. [Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2014-06-15

414

Photodissociation dynamics of benzoyl chloride at 235 nm: resonance-enhanced multiphoton ionization detection of Cl and HCl.  

PubMed

The photodissociation dynamics of benzoyl chloride at 235 nm has been investigated and compared with that of 2-furoyl chloride. Atomic Cl and molecular HCl channels have been detected in benzoyl chloride by employing resonance-enhanced multiphoton ionization technique and time-of-flight mass spectrometry. Both the Cl fragments, Cl((2)PJ=3/2, relative quantum yield 0.70 ± 0.15) and Cl*((2)PJ=1/2), show isotropic angular distribution and bimodal translational energy distributions. The predominant high kinetic energy channel contributes 72% to the C-Cl bond scission and arises from the S1 state having n?* character of benzoyl chloride. However, the low-energy Cl and HCl channels originate from the ground electronic state. The most plausible mechanism of HCl formation is proposed based on molecular orbital calculations. In contrast to benzoyl chloride, the HCl channel is not observed in 2-furoyl chloride on excitation at 235 nm, and this is attributed to an energy constraint. PMID:24471690

Saha, Ankur; Kawade, Monali; SenGupta, Sumana; Upadhyaya, Hari P; Kumar, Awadhesh; Naik, Prakash D

2014-02-20

415

Kinetic modeling of evolution of 3 + 1:Resonance enhanced multiphoton ionization plasma in argon at low pressures  

NASA Astrophysics Data System (ADS)

We present numerical kinetic modeling of generation and evolution of the plasma produced as a result of resonance enhanced multiphoton ionization (REMPI) in Argon gas. The particle-in-cell/Monte Carlo collision (PIC/MCC) simulations capture non-equilibrium effects in REMPI plasma expansion by considering the major collisional processes at the microscopic level: elastic scattering, electron impact ionization, ion charge exchange, and recombination and quenching for metastable excited atoms. The conditions in one-dimensional (1D) and two-dimensional (2D) formulations correspond to known experiments in Argon at a pressure of 5 Torr. The 1D PIC/MCC calculations are compared with the published results of local drift-diffusion model, obtained for the same conditions. It is shown that the PIC/MCC and diffusion-drift models are in qualitative and in reasonable quantitative agreement during the ambipolar expansion stage, whereas significant non-equilibrium exists during the first few 10 s of nanoseconds. 2D effects are important in the REMPI plasma expansion. The 2D PIC/MCC calculations produce significantly lower peak electron densities as compared to 1D and show a better agreement with experimentally measured microwave radiation scattering.

Tholeti, Siva Sashank; Shneider, Mikhail N.; Alexeenko, Alina A.

2014-06-01

416

Real-time mass-spectrometric study of the chemistry initiated by infrared-laser photolysis: CF 2HCl  

NASA Astrophysics Data System (ADS)

The infrared-laser photolysis/mass-spectrometric technique was used to monitor in real tune the free-radical and stable reactants and products in the reactive system initiated by multiphoton dissociation of CF 2HCl. The experimental observations indicate that in addition to the major channel CF 2HCl + nhv ? CF 2 + HCl, three additional minor channels exist: CFCl + HF, CHCl + F 2, and CHF + ClF. A reaction scheme is proposed.

Martinez, Richard I.; Herron, John T.

1981-11-01

417

Infrared Measurement  

NASA Technical Reports Server (NTRS)

A Jet Propulsion Laboratory Technical Support Package (TSP) describing a technique for processing data from an infrared radiometer assisted a manufacturer of laminates for printed circuit boards. To reduce emissions and lower the cost of producing prepreg (a continuous glass cloth, or web, impregnated with epoxy resin and partially cured by applying heat), Norplex Oak switched to infrared treating towers. The TSP confirmed the company's computer prediction of heat flux patterns, provided information that allowed the company to modify infrared treaters for consistency, and furnished a basis for development of optimal heater placements. The treaters are now successfully operating at increased speeds with improved product consistency.

1992-01-01

418

Why Infrared?  

ERIC Educational Resources Information Center

Discusses applications of techniques developed for the remote sensing of infrared radiation. In addition to military applications, remote sensing has become important in collecting environmental data and detecting ecological problems. (JR)

Harris, J. R.

1973-01-01

419

A combined resonance enhanced multiphoton ionization and ab initio study of the first absorption band of 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, and hexafluorobenzene  

NASA Astrophysics Data System (ADS)

The resonance enhanced multiphoton ionization (REMPI) spectra of jet-cooled penta- and hexafluorobenzene when excited in the region ?ex = 265-253 nm of the first absorption band and observed only in the CF+ mass channel is dominated by rotational structure in the A?X transition of CF. However, structure in the CF+ channel for ?ex > 265 nm is not a continuation of this CF spectrum and is assigned to vibrational activity in two low-frequency modes of a distorted excited state of the parent molecule. The vibrational structure is assigned to the lowest ??* state from a comparison with the equivalent spectrum of 1,2,4,5-tetrafluorobenzene. Ab initio calculations at the CIS level of theory of the ??* state of the penta- and hexafluorobenzene reveal a much more distorted equilibrium geometry (C1 symmetry) than that of 1,2,4,5-tetrafluorobenzene. Long progressions observed in the ?ex > 265 nm REMPI spectra of C6HF5 and C6F6 are assigned to two very low frequency (˜30 and 80 cm-1) modes. The role of the close-lying ??* and ??* states in determining the energy redistribution of the initially excited state by internal conversion is discussed. Both the fluorescent yield and the direct production of CF(X) are associated with transfer to the lower-lying ??* state.

Ridley, Trevor; Rogers, David M.; Lawley, Kenneth P.

2014-10-01

420

Identification and reactivity of the triplet excited state of 5-hydroxytryptophan.  

PubMed

Both the neurotransmitter serotonin and the unnatural amino acid 5-hydroxytryptophan (5HT), contain the 5-hydroxyindole chromophore. The photochemistry of 5HT is being investigated in relation to the multiphoton excitation of this chromophore to produce a characteristic photoproduct with green fluorescence ('hyperluminescence'). Laser flash photolysis (308 nm) of 5HT in aqueous solution at neutral pH produces both the neutral 5-indoloxyl radical (lambda(max) 400-420 nm) and another transient absorption with lambda(max) 480 nm and lifetime of 2 micros in deaerated solutions. Based on quenching by oxygen and beta-carotene, the species at 480 nm is identified as the triplet excited state of 5HT. In acidic solution a new oxygen-insensitive intermediate with lambda(max) 460 is assigned to the radical cation of 5HT. Time-resolved measurements of luminescence at 1270 nm have shown that the triplet state of 5HT is able to react with oxygen to form singlet excited oxygen (1O2*) with a quantum yield of approximately 0.1. However, 5HT has also been found to be an effective quencher of singlet oxygen with a second order rate constant of 1.3 x 10(8) dm3 mol(-1) s(-1). The results are discussed in the light of recent observations on the multiphoton-excited photochemistry of serotonin. PMID:15708522

Dad, S; Bisby, R H; Clark, I P; Parker, A W

2005-03-01

421

Imaging cells and extracellular matrix in vivo by using second-harmonic generation and two-photon excited fluorescence  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy relies on nonlinear light-matter interactions to provide contrast and optical sectioning capability for high-resolution imaging. Most multiphoton microscopy studies in biological systems have relied on two-photon excited fluorescence (TPEF) to produce images. With increasing applications of multiphoton microscopy to thick-tissue "intravital" imaging, second-harmonic generation (SHG) from structural proteins has emerged as a potentially important new contrast mechanism. However, SHG is typically detected in transmission mode, thus limiting TPEF/SHG coregistration and its practical utility for in vivo thick-tissue applications. In this study, we use a broad range of excitation wavelengths (730-880 nm) to demonstrate that TPEF/SHG coregistration can easily be achieved in unstained tissues by using a simple backscattering geometry. The combined TPEF/SHG technique was applied to imaging a three-dimensional organotypic tissue model (RAFT). The structural and molecular origin of the image-forming signal from the various tissue constituents was determined by simultaneous spectroscopic measurements and confirming immunofluorescence staining. Our results show that at shorter excitation wavelengths (<800 nm), the signal emitted from the extracellular matrix (ECM) is a combination of SHG and TPEF from collagen, whereas at longer excitation wavelengths the ECM signal is exclusively due to SHG. Endogenous cellular signals are consistent with TPEF spectra of cofactors NAD(P)H and FAD at all excitation wavelengths. The reflected SHG intensity follows a quadratic dependence on the excitation power, decays exponentially with depth, and exhibits a spectral dependence in accordance with previous theoretical studies. The use of SHG and TPEF in combination provides complementary information that allows noninvasive, spatially localized in vivo characterization of cell-ECM interactions in unstained thick tissues.

Zoumi, Aikaterini; Yeh, Alvin; Tromberg, Bruce J.

2002-08-01

422

Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states  

NASA Astrophysics Data System (ADS)

Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper [

F. Dell’Anno, S. De Siena, and F. Illuminati, Phys. Rev. A 69, 033812 (2004)
], we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of Hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing nondegenerate and degenerate multiphoton processes. We determine the coherent states associated with the canonical transformations, which generalize the nondegenerate two-photon squeezed states. Such heterodyne multiphoton squeezed states are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non-Gaussian, highly nonclassical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two-mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.

dell'Anno, Fabio; de Siena, Silvio; Illuminati, Fabrizio

2004-03-01

423

Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states  

SciTech Connect

Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper [F. Dell'Anno, S. De Siena, and F. Illuminati, Phys. Rev. A 69, 033812 (2004)], we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of Hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing nondegenerate and degenerate multiphoton processes. We determine the coherent states associated with the canonical transformations, which generalize the nondegenerate two-photon squeezed states. Such heterodyne multiphoton squeezed states are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non-Gaussian, highly nonclassical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two-mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.

Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, INFM UdR di Salerno, INFN Sezione di Napoli, Gruppo Collegato di Salerno, Via S. Allende, 84081 Baronissi, SA (Italy)

2004-03-01

424

Volume 81, number 3 CHEMICALPHYSICSLETTERS 1 August 1981 UNIMOLECULAR FRAGMENTATION KINETICS BY MULTIPHOTON IONIZATION  

E-print Network

calls for the use of vacuum ultra- violet (VUV) photoionization [2-4]. Unfortunately, the number tunable VUV radiation. An alternative to one-photon VUV photoionization is multiphoton ionization (MPI:: ~_.,~ pump ON ::1 / P DETECTOR I ~K 1 IsignaI L ............... F......... ~--- J l~, ,,._I ~ h POWER BEAM

Zare, Richard N.

425

Nondestructive Imaging of Live Human Keloid and Facial Tissue Using Multiphoton Microscopy  

Microsoft Academic Search

Objectives: To use multiphoton microscopy to image collagen fibers and matrix structure in nonfixed human keloid tissue and normal human facial skin obtained fol- lowing surgery and to compare the findings to existing knowledge of normal skin and keloid morphology to de- termine if this technology is a suitable adjunct for con- ventional histology. Methods: Epidermis was removed to expose

Victor Da Costa; Randy Wei; Ryan Lim; Chung-Ho Sun; Jimmy J. Brown; Brian J.-F. Wong

2008-01-01

426

Electron-nuclear energy sharing in above-threshold multiphoton dissociative ionization of H2.  

PubMed

We report experimental observation of the energy sharing between electron and nuclei in above-threshold multiphoton dissociative ionization of H2 by strong laser fields. The absorbed photon energy is shared between the ejected electron and nuclei in a correlated fashion, resulting in multiple diagonal lines in their joint energy spectrum governed by the energy conservation of all fragment particles. PMID:23889391

Wu, J; Kunitski, M; Pitzer, M; Trinter, F; Schmidt, L Ph H; Jahnke, T; Magrakvelidze, M; Madsen, C B; Madsen, L B; Thumm, U; Dörner, R

2013-07-12

427

Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2  

NASA Astrophysics Data System (ADS)

We report experimental observation of the energy sharing between electron and nuclei in above-threshold multiphoton dissociative ionization of H2 by strong laser fields. The absorbed photon energy is shared between the ejected electron and nuclei in a correlated fashion, resulting in multiple diagonal lines in their joint energy spectrum governed by the energy conservation of all fragment particles.

Wu, J.; Kunitski, M.; Pitzer, M.; Trinter, F.; Schmidt, L. Ph. H.; Jahnke, T.; Magrakvelidze, M.; Madsen, C. B.; Madsen, L. B.; Thumm, U.; Dörner, R.

2013-07-01

428

Resonance enhanced multiphoton ionization spectra of molecules and molecular fragments. Technical report, January 1990--December 1990  

SciTech Connect

The objective of our effort is to carry out theoretical studies of resonance enhanced multiphoton ionization processes in molecules and molecular fragments. These studies are designed to provide a quantitatively robust analysis and prediction of key spectral features of interest in several ongoing experimental studies and applications of this technique.

NONE

1997-07-01

429

Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2  

E-print Network

Electron-Nuclear Energy Sharing in Above-Threshold Multiphoton Dissociative Ionization of H2 J. Wu­4], where the photon energy is shared by the freed electrons and the nuclear fragments. For the molecular ionization [10­15], and the imaging of inter- nuclear distance using nuclear kinetic energy release spec- tra

Thumm, Uwe

430

Clinical combination of multiphoton tomography and high frequency ultrasound imaging for evaluation of skin diseases  

NASA Astrophysics Data System (ADS)

For the first time, high frequency ultrasound imaging, multiphoton tomography, and dermoscopy were combined in a clinical study. Different dermatoses such as benign and malign skin cancers, connective tissue diseases, inflammatory skin diseases and autoimmune bullous skin diseases have been investigated with (i) state-of-the-art and highly sophisticated ultrasound systems for dermatology, (ii) the femtosecond-laser multiphoton tomograph DermaInspectTM and (iii) dermoscopes. Dermoscopy provides two-dimensional color imaging of the skin surface with a magnification up to 70x. Ultrasound images are generated from reflections of the emitted ultrasound signal, based on inhomogeneities of the tissue. These echoes are converted to electrical signals. Depending on the ultrasound frequency the penetration depth varies from about 1 mm to 16 mm in dermatological application. The 100-MHz-ultrasound system provided an axial resolution down to 16 ?m and a lateral resolution down to 32 ?m. In contrast to the wide-field ultrasound images, multiphoton tomography provided horizontal optical sections of 0.36×0.36 mm2 down to 200 ?m tissue depth with submicron resolution. The autofluorescence of mitochondrial coenzymes, melanin, and elastin as well as the secondharmonic- generation signal of the collagen network were imaged. The combination of ultrasound and multiphoton tomography provides a novel opportunity for diagnostics of skin disorders.

König, K.; Speicher, M.; Koehler, M. J.; Scharenberg, R.; Elsner, P.; Kaatz, M.

2010-02-01

431

Multiphoton absorption cross section and virtual-state spectroscopy for the entangled n-photon state  

E-print Network

Multiphoton absorption cross section and virtual-state spectroscopy for the entangled n-photon absorption cross sections are also obtained. The absorption cross sections exhibit a linear dependence states involved in the interaction from the absorption cross section measured as a function of path delay

Teich, Malvin C.

432

Multiphoton imaging microscopy at deeper layers with adaptive optics control of spherical aberration  

NASA Astrophysics Data System (ADS)

Despite the inherent confocality and optical sectioning capabilities of multiphoton microscopy, three-dimensional (3-D) imaging of thick samples is limited by the specimen-induced aberrations. The combination of immersion objectives and sensorless adaptive optics (AO) techniques has been suggested to overcome this difficulty. However, a complex plane-by-plane correction of aberrations is required, and its performance depends on a set of image-based merit functions. We propose here an alterna