These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Infrared multiphoton excitation, dissociation and ionization of C 60  

NASA Astrophysics Data System (ADS)

We report the observation of mid-infrared multiphoton excitation, dissociation, and ionization of C 60 by shaped CO 2 laser pulses. The results are interpreted in the framework of the general statistical theory of infrared laser chemistry, adding some simple model assumptions. The observations on intensity- and fluence-dependent fragment ion distributions are consistent with a mechanism of vibrational preionization from energies exceeding the threshold for ionization by about a factor of 8.

Hippler, Michael; Quack, Martin; Schwarz, René; Seyfang, Georg; Matt, Sara; Märk, Tilmann

1997-10-01

2

Dynamics of infrared multiphoton dissociation of SF by molecular beam method. [Nonrandomize excitation energy  

Microsoft Academic Search

The decomposition of polyatomic molecules by infrared multiphoton absorption is a subject which is under extensive investigation in many laboratories. The process has been shown to be efficient, selective and collisionless. The physical principles which are mainly responsible for the absorption of a large number of photons by an isolated molecule under intense infrared laser radiation have been elucidated through

E. R. Grant; M. J. Coggiola; Y. T. Lee; P. A. Schulz; Y. R. Shen

1977-01-01

3

Volume 101, number 4.5 CHEMICAL PHYSICS LETTERS 28 October 1983 ENERGY DEPOSITION IN SO, VIA INTENSE INFRARED LASER MULTIPHOTON EXCITATION  

E-print Network

Volume 101, number 4.5 CHEMICAL PHYSICS LETTERS 28 October 1983 ENERGY DEPOSITION IN SO, VIA INTENSE INFRARED LASER MULTIPHOTON EXCITATION James V. TIETZ and Shill-1 CHU * Departnwnr of Ckmisr using the MPPA indicates thnt col- lisionless MPD xxill not be achieved at laser field strengths under

Chu, Shih-I

4

Multiphoton excited fluorescence spectroscopy of biomolecular systems  

Microsoft Academic Search

Recent work on the emerging application of multiphoton excitation to fluorescence studies of biomolecular dynamics and structure is reviewed. The fundamental principles and experimental techniques of multiphoton excitation are outlined, fluorescence lifetimes, anisotropy and spectra in membranes, proteins, hydrocarbons, skin, tissue and metabolites are featured, and future opportunities are highlighted.

David J. S. Birch

2001-01-01

5

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

6

Multiphoton microscopy with near infrared contrast  

E-print Network

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

Larson-Prior, Linda

7

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, November 1989October 1992  

Microsoft Academic Search

This research program has demonstrated the feasibility of using Infrared Multiphoton (IRMP) processes for reliable ignition and combustion enhancement of natural gas. Hydrocarbon constituents of natural gas are excited with focused, pulsed infrared lasers tuned to discrete resonant frequencies causing their dissociation to very reactive radicals. These radicals participate in chain-branching and chain-propagating reactions significantly improving the combustion of natural

M. Lavid; A. T. Poulos; S. K. Gulati; J. G. Stevens; W. R. Lempert

1993-01-01

8

Infrared multiphoton ignition and enhancement of combustion. Final report  

Microsoft Academic Search

The research demonstrated the feasibility of obtaining reliable ignition and enhancement of combustion by a novel concept, Infrared Multiphoton Absorption\\/Dissociation (IRMPA\\/IRMPD). A methanol-oxygen system was chosen to test this concept because methanol is a potential alternative fuel susceptible to IRMPD. Multiphoton absorption, dissociation, and ignition experiments were conducted in closed pyrex reaction cells with IR-transmitting NaCl windows. Various pressures of

M. Lavid; A. T. Poulos

1986-01-01

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

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis  

Microsoft Academic Search

It was reported that a novel detection method, continuous wave (CW)-based multiphoton excitation (MPE) fluorescence detection with diode laser (DL), has been firstly proposed for capillary electrophoresis (CE). Special design of end-column detection configuration proved to be superior to on-column type, considering the detection sensitivity. Three different kinds of fluorescent tags that were widely used as molecular label in bio-analysis,

Sheng Chen; Bi-Feng Liu; Ling Fu; Tao Xiong; Tiancai Liu; Zhihong Zhang; Zhen-Li Huang; Qiang Lu; Yuan-Di Zhao; Qingming Luo

2006-01-01

11

Infrared multiphoton ignition and enhancement of combustion. Final report  

SciTech Connect

The research demonstrated the feasibility of obtaining reliable ignition and enhancement of combustion by a novel concept, Infrared Multiphoton Absorption/Dissociation (IRMPA/IRMPD). A methanol-oxygen system was chosen to test this concept because methanol is a potential alternative fuel susceptible to IRMPD. Multiphoton absorption, dissociation, and ignition experiments were conducted in closed pyrex reaction cells with IR-transmitting NaCl windows. Various pressures of pure methanol and methanol-oxygen mixtures were irradiated with single pulses from a TEA CO/sub 2/ laser usually tuned at 10.33 micrometers and focused to fluences in the range 1-80 J/cm2. Temporal and spatial ignition behaviors were investigated and successful ignitions were obtained by multiphoton absorption processes. The research scope was expanded to include a second alcohol, 2-propanol.

Lavid, M.; Poulos, A.T.

1986-08-01

12

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, November 1989-October 1992  

SciTech Connect

This research program has demonstrated the feasibility of using Infrared Multiphoton (IRMP) processes for reliable ignition and combustion enhancement of natural gas. Hydrocarbon constituents of natural gas are excited with focused, pulsed infrared lasers tuned to discrete resonant frequencies causing their dissociation to very reactive radicals. These radicals participate in chain-branching and chain-propagating reactions significantly improving the combustion of natural gas. Experimental and computational tasks were performed to discern IR laser conditions needed to reliably obtain IRMP ignition and reduction in ignition delay time.

Lavid, M.; Poulos, A.T.; Gulati, S.K.; Stevens, J.G.; Lempert, W.R.

1993-11-30

13

Creation of particle-hole superposition states in graphene at multiphoton resonant excitation by laser radiation  

E-print Network

Nonlinear dynamics of establishment of electron-hole coherent superpositions states in graphene by multiphoton resonant excitation of interband transitions in laser fields is considered. The single-particle time dependent density matrix for such a quantized system is calculated in the multiphoton resonant approximation. The dependence of Rabi oscillations of Fermi-Dirac sea in graphene on the time, momentum, and photon number at multiphoton laser-excitation is analyzed.

H. K. Avetissian; A. K. Avetissian; G. F. Mkrtchian; Kh. V. Sedrakian

2011-12-07

14

Dissipation-sensitive multiphoton excitations of strongly interacting Rydberg atoms  

NASA Astrophysics Data System (ADS)

We theoretically investigate the effect of dissipation on multiphoton excitation of Rydberg atoms. The steady states and the dynamics are compared via two types of four-level excitation schemes with different dissipative paths of spontaneous emission. We find that in the case of strong Rydberg-Rydberg interaction, the schemes will settle in several different nonequilibrium steady states. The interesting aspect is that there exist the multistable steady states, which reveals the competition between interaction-induced nonlinearity and dissipation caused by spontaneous emission. A numerical simulation on the Rydberg population dynamics in the bistable region exhibits different features existing in the two schemes even with the same initial conditions, which accounts for the influence of the dissipation on the dynamics.

Qian, Jing; Zhang, Weiping

2014-09-01

15

Effect of intensity on fragment internal state distributions in the infrared multiphoton dissociation of vinyl cyanide  

E-print Network

dissociation of vinyl cyanide Charles M. Miller,a) John S. McKillop, and Richard N. Zare Department of in the infrared multiphoton dissociation of vinyl cyanide CH, = CHCN in a low pressure flowing gas. The rotational to this problem. This paper describes work on the infrared multiphoton dissociation of vinyl cyanide, CH2=CHCN

Zare, Richard N.

16

Dynamics of cavityless lasing generated by ultrafast multiphoton excitation  

SciTech Connect

A dynamical theory is developed with the purpose of explaining recent experimental results on multiphoton-excited amplified stimulated emission (ASE). Several conspicuous features of this experiment are analyzed, like the threshold dependence of the spectral profile on the pump intensity, and spectral shifts of the ASE pulses co- and counterpropagating relative to the pump pulse. Two models are proposed and evaluated, one based on the isolated molecule and another which involves solvent interaction. The spectral shift between the forward and backward ASE pulses arises in the first model through the competition between the ASE transitions from the pumped vibrational levels and from the bottom of the excited-state well, while in the solvent-related model the dynamical solute-solvent interaction leads to a relaxed excited state, producing an additional ASE channel. In the latter model the additional redshifted ASE channel makes the dynamics of ASE essentially different from that in the molecular model because the formation of the relaxed state takes a longer time. The variation of the pump intensity influences strongly the relative intensities of the different ASE channels and, hence, the spectral shape of ASE in both models. The regime of ASE changes character when the pump intensity crosses a threshold value. Such a phase transition occurs when the ASE rate approaches the rate of vibrational relaxation or the rate of solute-solvent relaxation in the first excited state.

Kimberg, Victor; Polyutov, Sergey; Gel'mukhanov, Faris; A ring gren, Hans; Baev, Alexander; Zheng Qingdong; He, Guang S. [Department of Theoretical Chemistry, Roslagstullsbacken 15, Royal Institute of Technology, S-106 91 Stockholm (Sweden); Institute for Lasers, Photonics and Biophotonics, State University of New York at Buffalo, Buffalo, New York 14260-3000 (United States)

2006-09-15

17

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis.  

PubMed

It was reported that a novel detection method, continuous wave (CW)-based multiphoton excitation (MPE) fluorescence detection with diode laser (DL), has been firstly proposed for capillary electrophoresis (CE). Special design of end-column detection configuration proved to be superior to on-column type, considering the detection sensitivity. Three different kinds of fluorescent tags that were widely used as molecular label in bio-analysis, such as small-molecule dye, fluorescent protein and nano particle or also referred to as quantum dot (QD), have been evaluated as samples for the constructed detection scheme. Quantitative analyses were also performed using rhodamine species as tests, which revealed dynamic linear range over two orders of magnitude, with detection limit down to zeptomole-level. Simultaneous detection of fluorescent dyestuffs with divergent excitation and emission wavelengths in a broad range showed advantage of this scheme over conventional laser-induced fluorescence (LIF) detection. Further investigations on CW-MPE fluorescence detection with diode laser for capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) separations of fluorescein isothiocyanate (FITC) labeled amino acids indicated good prospect of this detection approach in various micro or nano-column liquid phase separation technologies. PMID:16325835

Chen, Sheng; Liu, Bi-Feng; Fu, Ling; Xiong, Tao; Liu, Tiancai; Zhang, Zhihong; Huang, Zhen-Li; Lu, Qiang; Zhao, Yuan-Di; Luo, Qingming

2006-03-24

18

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

19

Collisionally enhanced isotopic selectivity in multiphoton dissociation of vibrationally excited CF3H  

NASA Astrophysics Data System (ADS)

We have studied infrared multiphoton dissociation of CF3H pre-excited to the second C-H stretch overtone under collisional conditions in view of developing a laser isotope separation scheme for carbon-13. This single stage process results in a C2F4 product that has been enriched in carbon-13 to a level as high as 99% starting from a naturally abundant sample, implying an isotopic selectivity in excess of 9000. While most of the selectivity is gained at the pre-excitation step, it can be increased up to a factor of 16 by collisions of the pre-excited 13CF3H species with room temperature molecules. This collision-induced enhancement in selectivity becomes evident from the dependence of the isotopic enrichment on both the total sample pressure and the time-delay between the two lasers, and we propose two different models that can account for this behavior. Finally, we evaluate the practical relevance of this two-laser scheme for isotope separation.

Boyarkin, O. V.; Kowalczyk, M.; Rizzo, T. R.

2003-01-01

20

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

21

Photodynamic therapy and knocking out of single tumor cells by multiphoton excitation processes  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) ultrashort laser pulses of 780 nm have been used to induce intracellular photodynamic reactions by nonlinear excitation of porphyrin photosensitizers. Intracellular accumulation and photobleaching of the fluorescent photosensitizers protoporphyrin IX and Photofrin (PF) have been studied by non-resonant two-photon fluorescence excitation of PF and aminolevulinic acid (ALA)-labeled Chinese hamster ovary (CHO) cells. To testify the efficacy of both substrates to induce irreversible destructive effects, the cloning efficiency (CE) of cells exposed to femtosecond pulses of a multiphoton laser scanning microscope (40x/1.3) was determined. In the case of Photofrin accumulation, CEs of 50% and 0% were obtained after 17 laserscans (2 mW?, 16 s/ frame) and 50 scans, respectively. All cells exposed to 50 scans died within 48h after laser exposure. 100 scans were required to induce lethal effects in ALA labeled cells. Sensitizer-free control cells could be scanned 250 times (1.1 h) and more without impact on the reproduction behavior, morphology, and vitality. In addition to the slow phototoxic effect by photooxidation processes, another destructive but immediate effect based on optical breakdown was induced when employing high intense NIR femtosecond laser beams. This was used to optically knock out single tumor cells in living mice (solid Ehrlich-Carcinoma) in a depth of 10 to 100 ?m.

Riemann, Iris; Fischer, Peter; Koenig, Karsten

2004-09-01

22

Investigations of multiphoton excitation and ionization in a short range potential  

SciTech Connect

We introduce an approach to the study of excitation and ionization for a system with a short range potential. In particular, analytical and numerical results are presented for the multiphoton ionization rate, under strong field conditions, of an electron confined by a delta-function potential. 9 refs., 3 figs.

Susskind, S.M.; Cowley, S.C.; Valeo, E.J.

1989-02-01

23

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

E-print Network

Measurement of Normal and Anomalous Diffusion of Dyes within Protein Structures Fabricated via dyes within these fabricated structures were found to be approximately 3-4 orders of magnitude slower of nonlinear multiphoton excited photochemistry. The mobility of fluorescent dyes of different mass

Wolgemuth, Charles

24

Infrared multiphoton decomposition of cis-2-pentene and 3-methyl-cis-2-pentene  

SciTech Connect

The infrared multiphoton (IRMP) decomposition of cis-2-pentene and 3-methyl-cis-2-pentene has been studied in order to compare the fragmentation pattern of the photoexcited molecules with that observed in the vacuum ultraviolet photolysis. The decompositions were studied at pressures from 0.2 to 5 Torr, using a pulsed CO/sub 2/ laser weakly focused to five fluences from about 5 to 20 J/cm/sup 2/ in the focal region. The IRMP decomposition of both molecules can be explained on the basis of a primary dissociation of a ..beta..C-C bond, followed by secondary fragmentation of the allylic moiety and the usual stabilizing processes and radical-radical reactions. The fragmentation patterns are generally similar to those observed in the vacuum UV photolysis, and the present results simply show the possibility that the ground state is involved in the vacuum UV photolysis; the behavior of the latter system itself lends support to this. Differences between the two systems can be explained by the higher initial energy of the molecules excited in the vacuum UVC. Some isomerization was also observed, mostly arising from radical-radical reactions. The formation of 1-pentene, however, indicates that the sigmatropic 1,3 hydrogen atom transfer can take place via the vibrationally excited ground state of cis-2-pentene. Conversely, 2-methyl-1-butene is not observed; its formation requires an internal methylene shift, and its occurrence in the vacuum UV photolysis suggests its direct formation from an electronically excited state.

Back, R.A.; Collin, G.J.

1986-10-23

25

Improved infrared multiphoton dissociation of peptides through N-terminal phosphonite derivatization  

Microsoft Academic Search

A strategy for improving the sequencing of peptides by infrared multiphoton dissociation (IRMPD) in a linear ion trap mass\\u000a spectrometer is described. We have developed an N-terminal derivatization reagent, 4-methylphosphonophenylisothiocyanate (PPITC),\\u000a which allows the attachment of an IR-chromogenic phosphonite group to the N-terminus of peptides, thus enhancing their IRMPD\\u000a efficiencies. After the facile derivatization process, the PPITC-modified peptides require shorter

Lisa A. Vasicek; Jeffrey J. Wilson; Jennifer S. Brodbelt

2009-01-01

26

5-HT spatial distribution imaging with multiphoton excitation of 5-HT correlative visible fluorescence in live cells  

NASA Astrophysics Data System (ADS)

The autofluorescence of 5-Hydroxytryptamine (5-HT) loaded rat mucosal mast cells (RBL-2H3 cells) is imaged with multiphoton excitation laser scanning microscope (MPELSM). 5-HT correlative visible fluorescence (Fco-vis) excited with 740-nm multiphoton excitation is observed in live cells for the first time, and the generating mechanism of 5-HT Fco-vis is studied. The spatial distribution of 5-HT in live cells is imaged at high spatial resolution in our experiment, which provides a new way to study the correlation between 5-HT spatial distribution and content, and the cellular functional state in live tissue or cells.

Zhang, Zhihong; Zeng, Shaoqun; Liu, Yafeng; Zhou, Wei; Chen, Tongsheng; Luo, Qingming

2002-04-01

27

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

28

Multiphoton imaging of quantum dot bioconjugates in cultured cells following Nd:YLF laser excitation  

NASA Astrophysics Data System (ADS)

Quantum dot bioconjugates offer unprecedented opportunities for monitoring biological processes and molecular interactions in cells, tissues, and organs. We are interested in developing applications that permit investigation of physiological processes and cytoskeletal organization in live cells, and allow imaging of complex organs, such as the auditory and vestibular sensory structures of the inner ear. Multiphoton microscopy is a powerful technique for acquiring images from deep within a sample while reducing phototoxic effects of laser light exposure on cells. Previous studies have established that a solid-state Nd:YLF laser can be used to acquire two-photon and three-photon images from live cells while minimizing phototoxic side effects (Wokosin et al., 1996, Bioimaging, 4:208-214; Squirrell et al., 1999, Nature Biotechnology, 8:763-767). We present here the results of experiments using an all-solid-state Nd:YLF 1047 nm femtosecond laser (Microlase DPM1000) source to excite quantum dot bioconjugates. Cells were labeled with Qdot (Quantum Dot Corporation) bioconjugates or with Alexa Fluor (Molecular Probes) bioconjugates and then imaged with a BioRad 1024 confocal microscope configured for multiphoton imaging using internal or external (non-descanned) detectors. Results demonstrate that the Nd:YLF laser can be used to stimulate fluorescence emission of quantum dots and Alexa Fluor bioconjugates in cultured amphibian (Xenopus) and mammalian (rat, chinese hamster) cells. We conclude that the Nd:YLF laser is a viable excitation source that extends the applicability of quantum dots for investigation of biological processes using multiphoton microscopy.

Serrano, Elba E.; Knight, V. B.

2005-04-01

29

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

PubMed

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

2014-08-01

30

Analysis of microparticle penetration into human and porcine skin: non-invasive imaging with multiphoton excitation microscopy  

NASA Astrophysics Data System (ADS)

At the University of Oxford and PowderJect Pharmaceuticals plc, a unique form of needle-free injection technology has been developed. Powdered vaccines and drugs in micro-particle form are accelerated in a high-speed gas flow to sufficient velocity to enter the skin, subsequently achieving a pharmaceutical effect. To optimize the delivery of vaccines and drugs with this method a detailed understanding of the interactive processes that occur between the microparticles and the skin is necessary. Investigations to date of micro-particle delivery into excised human and animal tissue have involved image analyses of histology sections. In the present study, a series of investigations were conducted on excised human and porcine skin using the technique of Multi-Photon fluorescence excitation Microscopy (MPM) to image particles and skin structures post-penetration. Micro-particles of various size and composition were imaged with infrared laser excitation. Three-dimensional images of stratum corneum and epidermal cell deformation due to micro-particle penetration were obtained. Measurements of micro-particle penetration depth taken from z-scan image stacks were used to successfully quantify micro-particle distribution within the skin, without invasively disrupting the skin target. This study has shown that MPM has great potential for the non-invasive imaging of particle skin interactive processes that occur with the transdermal delivery of powdered micro-particle vaccines and drugs.

Mulholland, William J.; Kendall, Mark A.; Bellhouse, Brian J.; White, Nick

2002-06-01

31

The resonance-enhanced multiphoton excitation spectrum of jet-cooled 4-H-1-benzopyrene-4-thione  

NASA Astrophysics Data System (ADS)

The multiphoton (one-colour) excitation spectrum of jet-cooled 4-H-1-benzopyrane-4-thione (BPT) is investigated in the wavelength region from 570 to 640 nm. The emission from BPT after multiphoton excitation was detected in two wide ranges in the blue (? 400-500 nm) and the near UV (? 250-400 nm). Resonance-enhanced excitation via the first excited triplet state S 0 ? T 1 ? ?' S,T is observed. The time dependence of the luminescence shows two components: (i) a fast decay component ( ?f < 50 ns), whose main part is assigned to S 2 ? S 0 fluorescence after two-photon excitation; (ii) a slow component ( ?s ? 2 ?s) which may be attributed to the emission from a photofragment (CS ?), efficiently created in a metastable triplet state by a four-photon absorption.

Ruth, A. A.; O'Keeffe, F. J.; Mansfield, M. W. D.; Brint, R. P.

1997-01-01

32

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

33

THE INTRAMOLECULAR VIBRATIONAL ENERGY DISTRIBUTION OF INFRARED MULTIPHOTON EXCITED MOLECULES  

E-print Network

taught me not only how to work, but also how to play. His insistence on quality and efficiency has shaped-Hsien Chen has gone through all the dirty work of setting up and carrying out the experiments with me; and Peter Saeta offered advice in Macintosh programming. I also enjoyed working with the other members

Mazur, Eric

34

Image-inspired 3D multiphoton excited fabrication of extracellular matrix structures by modulated raster scanning.  

PubMed

Multiphoton excited photochemistry is a powerful 3D fabrication tool that produces sub-micron feature sizes. Here we exploit the freeform nature of the process to create models of the extracellular matrix (ECM) of several tissues, where the design blueprint is derived directly from high resolution optical microscopy images (e.g. fluorescence and Second Harmonic Generation). To achieve this goal, we implemented a new form of instrument control, termed modulated raster scanning, where rapid laser shuttering (10 MHz) is used to directly map the greyscale image data to the resulting protein concentration in the fabricated scaffold. Fidelity in terms of area coverage and relative concentration relative to the image data is ~95%. We compare the results to an STL approach, and find the new scheme provides significantly improved performance. We suggest the method will enable a variety of cell-matrix studies in cancer biology and also provide insight into generating scaffolds for tissue engineering. PMID:24150376

Ajeti, Visar; Lien, Chi-Hsiang; Chen, Shean-Jen; Su, Ping-Jung; Squirrell, Jayne M; Molinarolo, Katharine H; Lyons, Gary E; Eliceiri, Kevin W; Ogle, Brenda M; Campagnola, Paul J

2013-10-21

35

Infrared multiphoton ignition and combustion enhancement of natural gas. Final report, February 1988-May 1989  

SciTech Connect

The Phase I feasibility study has demonstrated the potential of using Infrared Multiphoton (IRMP) processes for ignition and combustion enhancement of natural gas. Experiments with IR lasers were conducted to investigate the effects of IRMP techniques on methane, ethane, isotopically substituted surrogates, and sensitized mixtures. Major findings include: (1) Identification of HF/DF laser as an appropriate source for IRMP; (2) Demonstration of IRMP decomposition of deuterated methane with CO{sub 2} laser; (3) Successful IRMP ignition of deuterated methane and ethane mixtures; (4) Successful IRMP ignition of methane mixtures using photo-sensitizers. These experimental findings support the concept that IRMP processes are capable of dissociating methane, other minor constituents of natural gas, or sensitizers to reactive, combustion-enhancing radicals. A comprehensive Phase II contract to bring the concept closer to commercial implementation is underway.

Lavid, M.; Poulos, A.T.

1990-08-14

36

Excited triplet state spectroscopy in the infrared  

NASA Astrophysics Data System (ADS)

A new method for the investigation of the infrared spectra of metastable excitedelectronic states is presented. With a Fourier Transform infrared spectrometer as the probe and a CW Xe lamp source as the pump, the infrared spectrum of the lowest triplet state of triphenylene isolated in a N 2 matrix at 15K has been examined. CH out-of-plane wagging modes are prominent and shifted from their ground state frequencies. It is expected that when fully developed this method will provide important information on excited state force constants and potential energy surfaces.

Baiardo, Joseph; Mukherjee, Ranajit; Vala, Martin

1982-03-01

37

Interband photorefractive effect in beta-BBO crystal due to multiphoton excitation by intense ultrashort optical pulses.  

PubMed

This paper presents the first experimental observation of interband photo- refractive (PR) effects in beta-BBO crystal due to multiphoton excitation with intense ultrashort pulses. In order to fully characterize the PR effects, a sensitive intracavity scheme is developed to magnify the dynamics of nonlinear lenses induced by the PR effects. The reproducible PR phenomena depend strongly on the power, wavelength, and spatial intensity profile of the intense laser pulses and the electro-optic coefficient of the optical materials. Its response time is from tens of seconds to several minutes. The results may be very helpful for us to find a solution to overcome the deleterious influence of multiphoton induced photo-charges on nonlinear optical frequency conversions, e.g. optical parametric chirped pulse amplification. PMID:19547410

Xu, Shixiang; Cai, Hua; Zeng, Heping

2007-08-20

38

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

39

First in vivo animal studies on intraocular nanosurgery and multiphoton tomography with low-energy 80-MHz near-infrared femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

We report on a method for refractive laser surgery based on low-energy femtosecond laser pulses provided by ultracompact turn-key non-amplified laser systems. An additional excimer laser is not required for ablation of the stroma. The novel method has the potential to be used for (i) optical flap creation as well as stroma ablation and (ii) for non-invasive flap-free intrastromal ablation. In addition, 3D multiphoton imaging of the cornea can be performed. In particular, we used sub-nanojoule near infrared 80 MHz femtosecond laser pulses for multiphoton imaging of corneal structures with ultrahigh resolution (< 1?m) as well as for highly precise intraocular refractive surgery. Imaging based on two-photon excited cellular autofluorescence and SHG formation in collagen structures was performed at GW/cm2 intensities, whereas destructive optical breakdown for nanoprocessing occurred at TW/cm2 light intensities. These high intensities were realized with sub-nJ pulses within a subfemtoliter intrastromal volume by diffraction-limited focussing with high NA objectives and beam scanning 50 to 140 ?m below the epithelial surface. Multiphoton tomography of the cornea was used to determine the target of interest and to visualize intraocular post-laser effects. Histological examination with light- and electron microscopes of laser-exposed porcine and rabbit eyes reveal a minimum intratissue cut size below 1 ?m without destructive effects to surrounding collagen structures. LASIK flaps and intracorneal cavities could be realized with high precision using 200 fs, 80 MHz, sub-nanojoule pulses at 800 nm. First studies on 80 MHz femtosecond laser surgery on living rabbits have been performed.

Konig, Karsten; Wang, Bagui; Krauss, Oliver; Riemann, Iris; Schubert, Harald; Kirste, Sigrun; Fischer, Peter

2004-07-01

40

Excited state dynamics in SO2. III. An ab initio quantum study of single- and multi-photon ionization  

NASA Astrophysics Data System (ADS)

We present an ab initio quantum study of the photoelectron spectra of sulfur dioxide, based on wavepacket propagations on manifolds of ionic, and excited/Rydberg states. We obtain excellent agreement for two different cases. First, the one photon ionization case where we can reproduce all details of the experimental spectrum and demonstrate the influence of the conical intersection between two of the ionic states. Then the multiphoton ionization regime, in which the dynamics of the wave packet on the two lowest singlet states is directly mapped in the spectra via a pump-probe scheme, as proposed in the experimental companion paper [I. Wilkinson et al., J. Chem. Phys. 140, 204301 (2014)].

Lévêque, Camille; Köppel, Horst; Taïeb, Richard

2014-05-01

41

RECENT PROGRESS IN MULTIFOCAL MULTIPHOTON MICROSCOPY  

PubMed Central

Multifocal multiphoton microscopy (MMM) has recently become an important tool in biomedicine for performing three-dimensional fast fluorescence imaging. Using various beamsplitting techniques, MMM splits the near-infrared laser beam into multiple beamlets and produces a multifocal array on the sample for parallel multiphoton excitation and then records fluorescence signal from all foci simultaneously with an area array detector, which significantly improves the imaging speed of multiphoton microscopy and allows for high efficiency in use of the excitation light. In this paper, we discuss the features of several MMM setups using different beamsplitting devices, including a Nipkow spinning disk, a microlens array, a set of beamsplitting mirrors, or a diffractive optical element (DOE). In particular, we present our recent work on the development of an MMM using a spatial light modulator (SLM). PMID:24363782

LIU, LIXIN; SHAO, YONGHONG; NIU, HANBEN

2013-01-01

42

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

43

Infrared multiphoton dissociation of small-interfering RNA anions and cations.  

PubMed

Infrared multiphoton dissociation (IRMPD) on a linear ion trap mass spectrometer is applied for the sequencing of small interfering RNA (siRNA). Both single-strand siRNAs and duplex siRNA were characterized by IRMPD, and the results were compared with that obtained by traditional ion trap-based collision induced dissociation (CID). The single-strand siRNA anions were observed to dissociate via cleavage of the 5' P-O bonds yielding c- and y-type product ions as well as undergo neutral base loss. Full sequence coverage of the siRNA anions was obtained by both IRMPD and CID. While the CID mass spectra were dominated by base loss ions, accounting for approximately 25% to 40% of the product ion current, these ions were eliminated through secondary dissociation by increasing the irradiation time in the IRMPD mass spectra to produce higher abundances of informative sequence ions. With longer irradiation times, however, internal ions corresponding to cleavage of two 5' P-O bonds began to populate the product ion mass spectra as well as higher abundances of [a - Base] and w-type ions. IRMPD of siRNA cations predominantly produced c- and y-type ions with minimal contributions of [a - Base] and w-type ions to the product ion current; the presence of only two complementary series of product ions in the IRMPD mass spectra simplified spectral interpretation. In addition, IRMPD produced high abundances of protonated nucleobases, [G + H](+), [A + H](+), and [C + H](+), which were not detected in the CID mass spectra due to the low-mass cut-off associated with conventional CID in ion traps. CID and IRMPD using short irradiation times of duplex siRNA resulted in strand separation, similar to the dissociation trends observed for duplex DNA. With longer irradiation times, however, the individual single-strands underwent secondary dissociation to yield informative sequence ions not obtained by CID. PMID:20129797

Gardner, Myles W; Li, Na; Ellington, Andrew D; Brodbelt, Jennifer S

2010-04-01

44

Multiphoton-Excited Luminescent Lanthanide Bioprobes: Two- and Three-Photon Cross Sections of Dipicolinate Derivatives and Binuclear Helicates  

E-print Network

Multiphoton excited luminescent properties of water-soluble Eu III and Tb III complexes with derivatives of dipicolinic acid functionalized with a polyoxyethylene pendant arm and terminal groups, [Eu(L OMe)3] 3-, [Eu(L NH2)3] 3-, and [Tb(L OH)3] 3-, as well as of binuclear helicates with overall composition [Ln2(L CX)3] (X) 2, 5) are investigated. Characteristic emission from the 5 D0 and 5 D4 excited levels of Eu III and Tb III, respectively, upon ?800 nm excitation results from three-photon absorption (3PA) for [Eu(L OMe)3] 3-, [Eu(L NH2)3] 3-, [Tb(L OH)3] 3-, and [Ln2(L C2)3], while luminescence from [Eu2(L C5)3] is induced by two-photon absorption (2PA) owing to its 1PA spectrum extending further into the visible. The 3PA cross sections have been determined and are the first ones reported for lanthanide complexes: (i) those of Eu III and Tb III bimetallic helicates [Ln2(L C2)3] are 20 times larger compared to the corresponding values for tris(dipicolinates); (ii) derivatization of dipicolinic acid for Tb III complexes has almost no influence on the 3PA cross section; however, for Eu III complexes a ?2 times decrease is observed. The feasibility of [Eu2(L C5)3] as multiphoton luminescence bioprobe is demonstrated by two-photon scanning microscopy imaging experiments on HeLa cells incubated with this bimetallic helicate.

Svetlana V. Eliseeva; Gerald Auböck; Frank Van Mourik; Andrea Cannizzo; Bo Song; Emmanuel Deiters; Anne-sophie Chauvin; Majed Chergui; Jean-claude G. Bünzli

45

Excited state dynamics in SO2. III. An ab initio quantum study of single- and multi-photon ionization.  

PubMed

We present an ab initio quantum study of the photoelectron spectra of sulfur dioxide, based on wavepacket propagations on manifolds of ionic, and excited/Rydberg states. We obtain excellent agreement for two different cases. First, the one photon ionization case where we can reproduce all details of the experimental spectrum and demonstrate the influence of the conical intersection between two of the ionic states. Then the multiphoton ionization regime, in which the dynamics of the wave packet on the two lowest singlet states is directly mapped in the spectra via a pump-probe scheme, as proposed in the experimental companion paper [I. Wilkinson et al., J. Chem. Phys. 140, 204301 (2014)]. PMID:24880276

Lévêque, Camille; Köppel, Horst; Taïeb, Richard

2014-05-28

46

Molecular Hydrogen Excitation in Ultraluminous Infrared Galaxies  

E-print Network

We report medium resolution VLT ISAAC K-band spectroscopy of the nuclei of seven ultraluminous infrared galaxies. After accounting for stellar absorption features, we have detected several molecular hydrogen (H_2) v=1-0, 2-1, and 3-2 vibrational emission lines, as well as the HI Br\\gamma and HeI 2^1P-2^1S recombination lines. The relative H_2 line intensities show little variation between the objects, suggesting that the H_2 excitation mechanisms in the nuclei are similar in all the objects. The 1-0 emissions appear thermalised at temperatures T\\sim1000K. However, the 2-1 and 3-2 emissions show evidence of being radiatively excited by far-ultraviolet (FUV) photons, suggesting that the H_2 excitation in the ULIRGs may arise in dense photon dominated regions (PDRs). We show that the line ratios in the nuclei are consistent with PDRs with cloud densities between 10^4 to 10^5cm^{-3}, exposed to far ultraviolet (FUV) radiation fields at least 10^3 times more intense than the ambient FUV intensity in the local interstellar medium. We have constructed starburst models for the ULIRGs based on their H_2 properties, as well as on the intensities of the recombination lines. Our models provide a consistent picture of young 1-5Myr star clusters surrounded by relatively dense PDRs which are irradiated by intense FUV fluxes. Comparison to the inner few hundred parsecs of the Milky Way indicates that the star formation efficiency in ULIRGs is 10--100 times higher than in the Galactic Center.

R. I. Davies; A. Sternberg; M. Lehnert; L. E. Tacconi-Garman

2003-07-23

47

Compact non-contact total emission detection for in vivo multiphoton excitation microscopy.  

PubMed

We describe a compact, non-contact design for a total emission detection (c-TED) system for intra-vital multiphoton 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), whereas murine skeletal muscle and rat kidney showed gains of over two and just under twofold near the surface, respectively. Gains decreased with imaging depth (particularly in the kidney). Zebrafish imaging on a reflective substrate showed close to a twofold 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 multiphoton imaging methods is discussed. PMID:24251437

Combs, C A; Smirnov, A; Glancy, B; Karamzadeh, N S; Gandjbakhche, A H; Redford, G; Kilborn, K; Knutson, J R; Balaban, R S

2014-02-01

48

Multi-photon ionization and fragmentation of uracil: Neutral excited-state ring opening and hydration effects  

NASA Astrophysics Data System (ADS)

Multi-photon ionization (MPI) of the RNA base uracil has been studied in the wavelength range 220-270 nm, coinciding with excitation to the S2(??*) state. A fragment ion at m/z = 84 was produced by 2-photon absorption at wavelengths ?232 nm and assigned to C3H4N2O+ following CO abstraction. This ion has not been observed in alternative dissociative ionization processes (notably electron impact) and its threshold is close to recent calculations of the minimum activation energy for a ring opening conical intersection to a ?(n-?)?* closed shell state. Moreover, the predicted ring opening transition leaves a CO group at one end of the isomer, apparently vulnerable to abstraction. An MPI mass spectrum of uracil-water clusters is presented for the first time and compared with an equivalent dry measurement. Hydration enhances certain fragment ion pathways (particularly C3H3NO+) but represses C3H4N2O+ production. This indicates that hydrogen bonding to water stabilizes uracil with respect to neutral excited-state ring opening.

Barc, B.; Ryszka, M.; Spurrell, J.; Dampc, M.; Limão-Vieira, P.; Parajuli, R.; Mason, N. J.; Eden, S.

2013-12-01

49

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

50

Multiphoton dissociation of SF6 by a molecular beam method  

Microsoft Academic Search

The dynamics of infrared multiphoton excitation and dissociation of SF6 has been investigated under collision-free conditions by a crossed laser–molecular beam method. In order to understand the excitation mechanism and to elucidate the requirements of laser intensity and energy fluence, a series of experiments have been carried out to measure the dissociation yield dependences on energy fluence, vibrational temperature of

P. A. Schulz; E. R. Grant; Y. R. Shen; Y. T. Lee

1980-01-01

51

Multiphoton dissociation of SF6 by a molecular beam method  

Microsoft Academic Search

The dynamics of infrared multiphoton excitation and dissociation of SF6 has been investigated under collision-free conditions by a crossed laser-molecular beam method. In order to understand the excitation mechanism and to elucidate the requirements of laser intensity and energy fluence, a series of experiments have been carried out to measure the dissociation yield dependences on energy fluence, vibrational temperature of

P. A. Schulz; Aa. S. Sudbø; E. R. Grant; Y. R. Shen; Y. T. Lee

1980-01-01

52

Ultrafast multiphoton transient absorption of ?-carotene  

NASA Astrophysics Data System (ADS)

Multiphoton spectroscopy is able to directly excite electronic states, which are one-photon forbidden. Under single photon conditions, such one-photon forbidden states are exclusively populated via internal relaxation. Hence, transient absorption with two-photon excitation has the potential of clarifying complex relaxation networks by using aimed excitation. In this work we exploited ultrafast two-photon spectroscopy to investigate the excitation of dark states of ?-carotene in solution. After direct excitation of the vibronic manifold of S2Ag- from S 0 via two-photon transition, the characteristic internal conversion via hot-S 1 ? S 1 ? S 0 was observed in the respective spectral region. Additional slow dynamics in the blue-wing of excited-state absorption (ESA) and in the NIR were detected, which is not directly observable with one-photon excitation transient absorption. These features are associated here to resonant multiphoton processes, which lead simultaneously to ultrafast intersystem crossing between singlet and triplet systems as well as to excitation of doublet states. Furthermore, we identify a 340-400 fs relaxation component in the near-infrared region after two-photon resonant excitation and discuss the role of additional dark states ( 3Ag- and 1Bu-) in this process.

Buckup, Tiago; Weigel, Alexander; Hauer, Jürgen; Motzkus, Marcus

2010-07-01

53

Interleaved dual-wavelength multiphoton imaging system for heterologous FRET and versatile fluorescent protein excitation  

Microsoft Academic Search

Broad two-photon cross sections of fluorescent proteins allow excitation with a single wavelength of a tunable femtosecond pulsed laser but the brightness is sub-optimal and the cross-talk prevents sensitized emission FRET imaging in heterologous systems. We present a novel arrangement of a resonant scanning microscope capable of fast interline dual wavelength femtosecond excitation of pairs of fluorophores. This allows optimal

M. Anna Zal; Michelle Nelson; Tomasz Zal

2007-01-01

54

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

55

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

Microsoft Academic Search

Multicolor nonlinear microscopy of living tissue using two- and three-photon-excited intrinsic fluorescence combined with second harmonic generation by supermolecular structures produces im- ages 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, in- doleamines, and collagen provides crucial information for physi- ology and

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

2003-01-01

56

Laser-based multiphoton excitation processes in combustion diagnostics. Final report, October 1988October 1989  

Microsoft Academic Search

Light atomic species such as oxygen atoms (O) and hydrogen atoms (H) are fundamentally important in a wide variety of combustion related phenomena such as flame ignition, propagation, extinction, and in chemical flame reactions. Furthermore, they are difficult to detect by conventional laser based optical methods (laser induced fluorescence) in combustion environments because the necessary resonance excitation wavelengths fall far

B. E. Forch; A. W. Miziolek; J. B. Morris

1990-01-01

57

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

58

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

59

Infrared light excites cells by changing their electrical capacitance  

PubMed Central

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

60

Do the Infrared Emission Features Need Ultraviolet Excitation  

E-print Network

We present the results of imaging spectroscopy of the reflection nebula vdB 133, obtained with the infrared camera and circular variable filter wheel on the Infrared Space Observatory (ISO). Our observations reveal the infrared emission features (IEFs), at 6.2, 7.7, 8.6, 11.3, and 12.7 micron, and associated 5 -- 15 micron continuum emission. The stellar system illuminating vdB 133 has the lowest ratio of ultraviolet (shortward of 0.4 micron) to total flux of any stars demonstrated to date to excite the IEFs and associated continuum emission from adjacent interstellar dust, as opposed to circumstellar dust. The low fraction of UV flux from this system poses a problem for existing models for the emission mechanism and emitting material, which all require substantial UV radiation for the excitation of the IEFs and associated continuum.

K. I. Uchida; K. Sellgren; M. W. Werner

1997-11-18

61

Infrared emission and excitation in LMC HII regions  

NASA Technical Reports Server (NTRS)

The infrared excess (IRE) of the Large Magellanic Cloud (LMC) HII nebulae is found to correlate positively with the temperature of the ambient radiation field or with the He(+)/H(+) abundance ratio. This result is discussed in terms of a selective absorption of the photons in the range 504 to 912 A relative to the He ionizing photons. This interpretation may explain the paradox of finding highly excited nebulae with only relatively moderate equivalent width of their Balmer lines.

Ungerer, V.; Viallefond, F.

1987-01-01

62

In vivo Drug Screening in Human Skin Using Femtosecond Laser Multiphoton Tomography  

Microsoft Academic Search

The novel femtosecond laser multiphoton imaging system DermaInspect forin vivotomography of human skin was used to study the diffusion and intradermal accumulation of topically applied cosmetic and pharmaceutical components. Near-infrared 80 MHz picojoule femtosecond laser pulses were employed to excite endogenous fluorophores and fluorescent components of a variety of ointments via a two-photon excitation process. In addition, collagen was imaged

K. König; A. Ehlers; F. Stracke; I. Riemann

2006-01-01

63

Multifocal multiphoton microscopy with adaptive optical correction  

NASA Astrophysics Data System (ADS)

Fluorescence lifetime imaging microscopy (FLIM) is a well established approach for measuring dynamic signalling events inside living cells, including detection of protein-protein interactions. The improvement in optical penetration of infrared light compared with linear excitation due to Rayleigh scattering and low absorption have provided imaging depths of up to 1mm in brain tissue but significant image degradation occurs as samples distort (aberrate) the infrared excitation beam. Multiphoton time-correlated single photon counting (TCSPC) FLIM is a method for obtaining functional, high resolution images of biological structures. In order to achieve good statistical accuracy TCSPC typically requires long acquisition times. We report the development of a multifocal multiphoton microscope (MMM), titled MegaFLI. Beam parallelization performed via a 3D Gerchberg-Saxton (GS) algorithm using a Spatial Light Modulator (SLM), increases TCSPC count rate proportional to the number of beamlets produced. A weighted 3D GS algorithm is employed to improve homogeneity. An added benefit is the implementation of flexible and adaptive optical correction. Adaptive optics performed by means of Zernike polynomials are used to correct for system induced aberrations. Here we present results with significant improvement in throughput obtained using a novel complementary metal-oxide-semiconductor (CMOS) 1024 pixel single-photon avalanche diode (SPAD) array, opening the way to truly high-throughput FLIM.

Coelho, Simao; Poland, Simon; Krstajic, Nikola; Li, David; Monypenny, James; Walker, Richard; Tyndall, David; Ng, Tony; Henderson, Robert; Ameer-Beg, Simon

2013-02-01

64

Competitive ionization processes of anthracene excited with a femtosecond pulse in the multi-photon ionization regime.  

PubMed

To clarify the ionization mechanism of large molecules under multi-photon ionization conditions, photo-electron spectroscopic studies on anthracene have been performed with electron imaging technique. Electron kinetic energy distributions below a few eV reveal that three kinds of ionization channels coexist, viz., vertical ionization, ionization from Rydberg states, and thermionic hot electron emission. Their relative yield is determined by the characteristic of the laser pulse. The duration in particular influences the ratio between the first two processes, while for higher intensities the last process dominates. Our results provide strong evidence that internal conversion plays an important role for the ionization of the molecule. PMID:22149795

Goto, M; Hansen, K

2011-12-01

65

Rotational structure of a super-excited state of the NO molecule revealed by OODR-multiphoton laser spectroscopy.  

PubMed

The optical-optical double resonance time of flight (OODR-TOF) spectroscopy technique was employed to examine the 65,000-66,500 cm(-1) region of the nitric oxide spectrum. In this region, we detected the following three electronic states: E (2)Sigma(+) (nu = 2) (Rydberg state), B (2)Pi (nu = 23) (valence state), and L (2)Pi (nu = 4) (valence state). The rotational structure analysis of an unexpected band in the red part of the spectra revealed the presence of a new super-excited (2)Sigma(+) Rydberg state at approximately 13.3 eV, which was populated through a three-photon transition from the intermediate A (2)Sigma(+) (nu = 0) state. This super-excited state converges to the NO (a(3)Sigma(+)) ionic state with electronic configuration (1sigma)(2)(2sigma)(2)(3sigma)(2)(4sigma)(2)(5sigma)(2)(1pi)(3)(2pi)(1)(3ssigma)(1). PMID:19788197

Lin, Yong-Ge; Colón-García, Jorge E; Cabrera, Carlos R; Quiñones, Edwin

2009-10-22

66

Gas phase ion formation from a liquid beam of arginine in aqueous solution by IR multiphoton excitation  

NASA Astrophysics Data System (ADS)

A liquid beam of aqueous solutions of arginine (AH), its hydrochloric acid salt (AH 2Cl) and its sodium salt (ANa) was irradiated with a pulsed IR laser at 3509 cm -1 (2.85 ?m). Positive and negative ions ejected to the gas phase were mass analyzed. From the AH 2Cl and the ANa aqueous solutions, the pre-existing ions in the solution were ejected directly to the gas phase. From the AH solution, on the other hand, both a protonated arginine ion, AH2+ and an argininate ion, A - were observed in the gas phase. Production of these ions is accounted for the four-photon excitation of water molecules in the solution.

Kohno, Jun-ya; Toyama, Namiki; Buntine, Mark A.; Mafuné, Fumitaka; Kondow, Tamotsu

2006-03-01

67

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

Microsoft Academic Search

The vibrational to translational (VâT) 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

P. M. Y

1991-01-01

68

Quantum dot infrared photodetector enhanced by surface plasma wave excitation  

E-print Network

.5403) Plasmonics; (310.6628) Subwavelength structures, nanostructures. References and links 1. For a recent review. Zhang, "Plasmon lasers at deep subwavelength scale," Nature 461(7264), 629­632 (2009). 4. S. R. J codes: (130.3060) Infrared; (230.5160) Photodetectors; (240.6680) Surface plasmons; (250

Krishna, Sanjay

69

Probing the infrared quark mass from highly excited baryons.  

PubMed

We argue that three-quark excited states naturally group into quartets, split into two parity doublets, and that the mass splittings between these parity partners decrease higher up in the baryon spectrum. This decreasing mass difference can be used to probe the running quark mass in the midinfrared power-law regime. A measurement of masses of high-partial-wave Delta* resonances should be sufficient to unambiguously establish the approximate degeneracy. We test this concept with the first computation of excited high-j baryon masses in a chirally invariant quark model. PMID:19792789

Bicudo, P; Cardoso, M; Van Cauteren, T; Llanes-Estrada, Felipe J

2009-08-28

70

Probing the Infrared Quark Mass from Highly Excited Baryons  

SciTech Connect

We argue that three-quark excited states naturally group into quartets, split into two parity doublets, and that the mass splittings between these parity partners decrease higher up in the baryon spectrum. This decreasing mass difference can be used to probe the running quark mass in the midinfrared power-law regime. A measurement of masses of high-partial-wave DELTA* resonances should be sufficient to unambiguously establish the approximate degeneracy. We test this concept with the first computation of excited high-j baryon masses in a chirally invariant quark model.

Bicudo, P.; Cardoso, M. [CFTP, Departamento de Fisica, Instituto Superior Tecnico, Lisboa (Portugal); Van Cauteren, T. [Department of Subatomic and Radiation Physics, Ghent University, Ghent (Belgium); Llanes-Estrada, Felipe J. [Departamento de Fisica Teorica I, Universidad Complutense de Madrid, Madrid (Spain)

2009-08-28

71

Multiphoton imaging of corneal tissue with near-infrared femtosecond laser pulses: corneal optical tomography and its use in refractive surgery  

NASA Astrophysics Data System (ADS)

The two-photon-mediated autofluorescence and second harmonic generation (SHG) are acting as a novel diagnostic tool to perform tissue optical tomography with submicron resolution. The three-dimensional corneal ultrastructure of whole depth can be probed without any staining or mechanical slicing. Compared with photodisruptive surgical effects occurring at TW/cm2 light intensity, multiphoton imaging can be induced at MW-GW/cm2 photon intensity. The multiphoton microscopy based on nonlinear absorption of femtosecond laser pulses at the wavelength of 715-930nm emitted from solid-state Ti: sapphire system is being used as a precise non-invasive monitoring tool to determine the interest of region, to visualize and to verify the outcomes in the invivo intrastromal laser nanosurgery. More interesting, the activated keratocytes have been also observed in-vivo 24 hours after the laser nanosurgery with this system. Overall, these data suggest that multiphoton microscopy is a highly sensitive and promising technique for studying the morphometric properties of the microstructure of the corneal tissue and for assessing the intrastromal nanosurgery. With the help of the multiphoton-mediated imaging, the next generation of laser refractive surgery approaches based on the nonamplified femtosecond lasers with higher precision and less complications are being evaluated systematically.

Wang, Bao-Gui; Koenig, Karsten; Riemann, Iris; Schubert, Harald; Halbhuber, Karl-Juergen

2006-02-01

72

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

73

In-vivo corneal nonlinear optical tomography based on second harmonic and multiphoton autofluorescence imaging induced by near-infrared femtosecond lasers with rabbits  

Microsoft Academic Search

The intratissue multiphoton autofluorescence imaging (MAI) and the second harmonic generation (SHG) based on nonlinear process of femtosecond nanojoule laser pulses at wave length of 750-850 nm emitted from solid-state Titanium: Sapphire Chameleon have been used as a highly precise non-destructive tool to realize the in-vivo differentiation of corneal layers with the assistance of intratissue optical tomography and to visualize

Baogui Wang; Karl-Juergen Halbhuber; Iris Riemann; Karsten Koenig

2005-01-01

74

Collisional relaxation of highly vibrationally excited CF2O prepared with different initial energies and distribution functions  

Microsoft Academic Search

The collisional relaxation of highly vibrationally excited CF2O* molecules prepared by infrared laser multiphoton absorption is compared with the results obtained when CF2O* is generated as a product of the reactions of CF3 and CF2Cl radicals with NO2. The three methods produce molecules with probably different energy distributions and also different average excitation energies ?E?. Thus, IR laser excitation results

G. A. Pino; C. A. Rinaldi; E. A. Coronado; J. C. Ferrero

1999-01-01

75

Collisional relaxation of highly vibrationally excited CF2O prepared with different initial energies and distribution functions  

Microsoft Academic Search

The collisional relaxation of highly vibrationally excited CF2O* molecules prepared by infrared laser multiphoton absorption is compared with the results obtained when CF2O* is generated as a product of the reactions of CF3 and CF2Cl radicals with NO2. The three methods produce molecules with probably different energy distributions and also different average excitation energies . Thus, IR laser excitation results

G. A. Pino; C. A. Rinaldi; E. A. Coronado; J. C. Ferrero

1999-01-01

76

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

77

Multiphoton absorption induced amplified spontaneous emission from biocatalyst-synthesized ZnO nanorods  

NASA Astrophysics Data System (ADS)

Multiphoton absorption-induced photoluminescence and amplified spontaneous emission (ASE) have been observed from ZnO nanorod arrays upon near-infrared excitation (?exc˜800nm). A low threshold of ˜12mJ/cm2 was demonstrated for the ASE process. The ultraviolet emission can be attributed to the recombination of carriers coexcited by the processes of three-photon and off-resonant two-photon absorption, which was confirmed by the excitation wavelength-dependent experiments. Additionally, it has been observed that the processes of ASE and second harmonic generation in ZnO nanorods appear to enhance each other when the excitation wavelength approaches the resonant wavelength for two-photon absorption.

Zhang, Chunfeng; Zhang, Fan; Qian, Shixiong; Kumar, Nitin; Hahm, Jong-in; Xu, Jian

2008-06-01

78

In-vivo corneal nonlinear optical tomography based on second harmonic and multiphoton autofluorescence imaging induced by near-infrared femtosecond lasers with rabbits  

NASA Astrophysics Data System (ADS)

The intratissue multiphoton autofluorescence imaging (MAI) and the second harmonic generation (SHG) based on nonlinear process of femtosecond nanojoule laser pulses at wave length of 750-850 nm emitted from solid-state Titanium: Sapphire Chameleon have been used as a highly precise non-destructive tool to realize the in-vivo differentiation of corneal layers with the assistance of intratissue optical tomography and to visualize the keratocyte structures and collagen lamellas with submicron resolution. Multiphoton nonlinear imaging occurs only with high light intensity on an order of MG-GW/cm2 and photon flux density of more than 1024 photons cm-2s-1 in a 0.1femtoliter intrastromal focus volume obtained by diffraction-limited focussing with high-numerical objectives. This technique, acting as a novel diagnostic tool, proved to be essential for femtosecond (fs) nanojoule (nJ) cornea surgery to determine the interest of region preoperation, to visualize and verify the outcomes immediately after the laser surgery and has potential to become a powerful tool in advancing understanding of corneal biomechnics and cellular reactions after laser induced lesion.

Wang, Baogui; Halbhuber, Karl-Juergen; Riemann, Iris; Koenig, Karsten

2005-10-01

79

The spread of excitation in neocortical columns visualized with infrared-darkfield videomicroscopy.  

PubMed

A combination of darkfield techniques and infrared videomicroscopy was used to measure the intrinsic optical signal (IOS) in slices of adult rat neocortex. The IOS, which reflects changes in light transmittance and scattering, provides a means of studying the spread of neuronal excitation and its modulation with high sensitivity and spatial resolution. The column-like IOS elicited by orthodromic stimulation is in accordance with models of neocortical circuitry. Blockade of synaptic transmission by the glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D-2-amino-5-phosphovaleric acid (D-APV) reduced the IOS. The GABAA agonist muscimol and the neuroactive steroid 5 alpha-tetrahydrodeoxy-corticosterone (5 alpha-THDOC) decreased the spread of excitation, whereas the GABAA antagonist bicuculline increased it. The present data suggest that the spatial spread of excitation in different neocortical layers is delimited by GABAergic inhibition mediated by the activation of GABAA receptors. PMID:8904754

Dodt, H U; D'Arcangelo, G; Pestel, E; Zieglgänsberger, W

1996-07-01

80

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

E-print Network

We present NIR observations of a sample of mainly interacting ULIRGs, 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 previous results for this galaxy. The [SiVI] emission line was detected in IRAS17179 and IRAS20210, both classified as Sy2s. Two of the sample were unclassified, IRAS00150 and IRAS23420, which exhibit neither [SiVI] emission or 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 indicate for IRAS20210 10 per cent, and for both IRAS23365 and IRAS23420, 30 per cent of their 1-0S(1) line emission has a non-thermal origin.

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

2001-06-04

81

Cell assay using a two-photon-excited europium chelate  

PubMed Central

We report application of two-photon excitation of europium chelates to immunolabeling of epidermal growth factor receptor (EGFR) cell surface proteins on A431 cancer cells. The europium chelates are excited with two photons of infrared light and emit in the visible. Europium chelates are conjugated to antibodies for EGFR. A431 (human epidermoid carcinoma) cells are labeled with this conjugate and imaged using a multiphoton microscope. To minimize signal loss due to the relatively long-lived Eu3+ emission, the multiphoton microscope is used with scanning laser two-photon excitation and non-scanning detection with a CCD. The chelate labels show very little photobleaching (less than 1% during continuous illumination in the microscope for 20 minutes) and low levels of autofluorescence (less than 1% of the signal from labeled cells). The detection limit of the europium label in the cell assay is better than 100 zeptomoles. PMID:21833362

Xiao, Xudong; Haushalter, Jeanne P.; Kotz, Kenneth T.; Faris, Gregory W.

2011-01-01

82

IMAGE RECONSTRUCTION OF MULTIPHOTON MICROSCOPY DATA  

PubMed Central

The techniques introduced in this paper allow for accurate multi-scale image reconstruction of multi-photon microscopy data. Multi-photon microscopy (MPM) is a tool for the non-invasive imaging of living organisms and tissue. The data acquired using this technique can contain information about the position, excited state lifetime, and spectra of the observed photons. The small number of photons collected, however, limits the quality of the reconstruction. The multiscale framework in this paper results in an accurate representation of both the intensity and excited state lifetime information. Using a multiscale reconstruction approach based on a penalized likelihood function, the underlying image is more accurately represented as compared to a naive aggregate binning approach. PMID:22158826

Doot, Jared M.; Eliceiri, Kevin W.; Nowak, Robert D.; Willett, Rebecca

2011-01-01

83

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

E-print Network

N-H Stretching Excitations in Adenosine-Thymidine Base Pairs in Solution: Pair Geometries, Infrared 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

Mukamel, Shaul

84

Multiphoton Processes in Homopolar Diatomic Molecules  

Microsoft Academic Search

Within the framework of time-dependent perturbation theory and the Born-Oppenheimer approximation, general expressions are derived for the cross sections of multiphoton processes induced by radiation acting on a homopolar diatomic molecule. A Morse-type model of potential-energy curves of excited electronic states is proposed which gives a good representation of true curves. The procedure used to evaluate the sums over intermediate

F. V. Bunkin; I. I. Tugov

1973-01-01

85

Multi-excitation near infrared (NIR) spectral fluorescence imaging using organic fluorophores  

NASA Astrophysics Data System (ADS)

The ability to obtain multi-color fluorescent imaging in vivo simultaneously using multi-targeted imaging probes could be of potential benefit from both a research and a clinical perspective. However, the simultaneous acquisition of more than 2 separate organic fluorophores usually requires more than one excitation source, since a single excitation source may not optimally excite all the fluorophores. In this study, we employed a multi-excitation approach in order to acquire optimized images with multiple near infrared (NIR) organic fluorophores at the same time. Using 3 sets of excitation filters (595+/-20nm, 640+/-25nm, 688+/-17nm) to acquire 3 distinct spectra and spectral unmixing software (CRi, Woburn, MA), it was possible to resolve the emission spectra of each of the NIR fluorophores using commercial software (Nuance, CRi, Woburn, MA) To demonstrate the utility of this approach 2 mouse models were investigated; In one model, mice bearing four implanted malignancies were injected with a cocktail of 3 fluorescently labeled monoclonal antibodies, each with its own distinct NIR fluorophore. In the second model five different lymph node drainage basins were imaged with 5-color dendrimer-based lymphatic imaging agents tagged with 5 different NIR fluorophores. We successfully detected each of the targeted tumors in the first model and all of the lymph nodes by their distinct color in the second model; neither of which would have been possible using the single excitation method. In conclusion, multi-excitation NIR spectral fluorescence imaging is feasible in a reasonable time frame and opens the possibility for in vivo immunohistochemical imaging (IHCi).

Kobayashi, Hisataka; Koyama, Yoshinori; Barrett, Tristan; Hama, Yukihiro; Choyke, Peter L.

2008-02-01

86

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

87

Multiphoton tomography of intratissue tattoo nanoparticles  

NASA Astrophysics Data System (ADS)

Most of today's intratissue tattoo pigments are unknown nanoparticles. So far, there was no real control of their use due to the absence of regulations. Some of the tattoo pigments contain carcinogenic amines e.g. azo pigment Red 22. Nowadays, the European Union starts to control the administration of tattoo pigments. There is an interest to obtain information on the intratissue distribution, their interaction with living cells and the extracellular matrix, and the mechanisms behind laser tattoo removal. Multiphoton tomographs are novel biosafety and imaging tools that can provide such information non-invasively and without further labeling. When using the spectral FLIM module, spatially-resolved emission spectra, excitation spectra, and fluorescence lifetimes can pr provided. Multiphoton tomographs are used by all major cosmetic comapanies to test the biosafety of sunscreen nanoparticles.

König, Karsten

2012-02-01

88

Coherent Control in Multiphoton Fluorescence Imaging  

PubMed Central

In multiphoton fluorescence laser-scanning microscopy ultrafast laser pulses, i.e. light pulses having pulse-width ? 1picosecond (1 ps = 10?12 s), are commonly used to circumvent the low multiphoton absorption cross-sections of common fluorophores. Starting with a discussion on how amplitude modulation of ultrashort pulse-train enhances the two-photon fluorescence providing deep insight into laser-induced photo-thermal damage, the effect of controlling time lag between phase-locked laser pulses on imaging is described. In addition, the prospects of laser pulse-shaping in signal enhancement (by temporal pulse-compression at the sample) and selective excitation of fluorophores (by manipulating the phase and/or amplitude of different frequency components within the pulse) are discussed with promising future applications lying ahead. PMID:23814444

De, Arijit Kumar; Goswami, Debabrata

2013-01-01

89

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

90

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

91

Multiphoton Biomedical Imaging and Photodynamic Therapy: Agents & Applications  

E-print Network

Multiphoton Biomedical Imaging and Photodynamic Therapy: Agents & Applications Kevin D. Belfield-reactive model Hydrophobic and hydrophilic dyes Two-Photon Photodynamic Therapy #12;"Two-photon laser scanning at the focus of the scanning pulsed-infrared laser beam, resulting in a much less harmful light dose during

Van Stryland, Eric

92

Excited state dynamics of a PYP chromophore model system explored with ultrafast infrared spectroscopy  

NASA Astrophysics Data System (ADS)

We perform ultrafast polarization sensitive visible pump-infrared probe spectroscopy on deprotonated trans- S-phenyl-thio- p-hydroxycinnamate, a model compound for photoactive yellow protein. We derive structural information from the observed bleach signals by comparison of the experimental frequency positions and anisotropies with results from quantum chemical calculations. The electronically excited state decays with 8 or 15 ps time constants for 1:1 or 10:1 DMSO:buffer, respectively, with a quantum yield for isomerization product formation less than 5%. Comparison of our results with earlier reported work on model compounds and on photoactive yellow protein (PYP) suggests an intricate tuning mechanism of the protein environment for the relaxation dynamics of PYP.

Usman, Anwar; Mohammed, Omar F.; Heyne, Karsten; Dreyer, Jens; Nibbering, Erik T. J.

2005-01-01

93

Multiphoton fluorescence microscopy in biology  

NASA Astrophysics Data System (ADS)

The inherent advantages of nonlinear excitation make multiphoton fluorescence microscopy (MPFM) awell-suited imaging technique for extracting valuable information from turbid and thick biological samples. These advantages include high three-dimensional spatial resolution, large penetration depth, minimum out-of-focus cellular photodamage, and high signal-to-noise contrast. We have investigated the nonlinear spectroscopy of biologically important molecules such as NADH, flavins, and intrinsically fluorescent proteins. Fundamental understanding of the molecular spectroscopy and dynamics of these biomolecules is essential for advancing their applications in biological research. MPFM has been utilized for monitoring a large spectrum of biological processes including metabolic activity and exocytosis. We will discuss two-photon (2P) redox fluorescence microscopy of NADH, which gives a quantitative measure of the respiratory chain activity, thus allowing functional imaging of energy metabolism in neurons and native brain tissue. Finally, a rational design strategy, based on donor-acceptor-donor configuration, will be elucidated for fluorescent probes with large 2P-excitation cross-section. These dyes are water-soluble, yet possess a high affinity to organic phases with site-specific labeling and Ca+2 sensitivity (Kd ~ 350 nM). A brief account on the biological application of nanocrystals and second harmonic imaging will be reviewed.

Heikal, Ahmed A.; Webb, Watt W.

2002-11-01

94

The near-infrared excitation of the HH211 protostellar outflow  

E-print Network

The protostellar outflow HH211 is of considerable interest since it is extremely young and highly collimated. Here, we explore the outflow through imaging and spectroscopy in the near-infrared to determine if there are further diagnostic signatures of youth. We confirm the detection of a near-infrared continuum of unknown origin. We propose that it is emitted by the driving millimeter source, escapes the core through tunnels, and illuminates features aligning the outflow. Narrow-band flux measurements of these features contain an unusually large amount of continuum emission. [Fe II] emission has been detected and is restricted to isolated condensations. However, the characteristics of vibrational excitation of molecular hydrogen resemble those of older molecular outflows. We attempt to model the ordered structure of the western outflow as a series of shocks, finding that bow shocks with J-type dissociative apices and C-type flanks are consistent. Moreover, essentially the same conditions are predicted for all three bows except for a systematic reduction in speed and density with distance from the driving source. We find increased K-band extinctions in the bright regions as high as 2.9 magnitudes and suggest that the bow shocks become visible where the outflow impacts on dense clumps of cloud material. We propose that the outflow is carved out by episodes of pulsating jets. The jets, driven by central explosive events, are responsible for excavating a central tunnel through which radiation temporarily penetrates.

Barry O'Connell; Michael D. Smith; Dirk Froebrich; Christopher J. Davis; Jochen Eisloeffel

2005-02-04

95

H{sub 2} EJECTION FROM POLYCYCLIC AROMATIC HYDROCARBONS: INFRARED MULTIPHOTON DISSOCIATION STUDY OF PROTONATED ACENAPHTHENE AND 9,10-DIHYDROPHENANTHRENE  

SciTech Connect

The infrared multiple-photon dissociation (IRMPD) spectra of protonated acenaphthene ([ACN+H]{sup +}) and 9,10-dihydrophenanthrene ([DHP+H]{sup +}) 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]{sup +} and [DHP+H]{sup +} have been calculated for H and H{sub 2} loss. The lowest energy barriers are for loss of H{sub 2}, with predicted energies 4.28 and 4.15 eV, respectively. After H{sub 2} ejection, the adjacent aliphatic hydrogens migrate to the bare ejection site and stabilize the remaining fragment. Single H loss may occur from [ACN+H]{sup +} but the energy required is higher. No single H loss is predicted from [DHP+H]{sup +}, 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; Vala, Martin T. [Department of Chemistry and Center for Chemical Physics, P.O. Box 117200, University of Florida, Gainesville, FL 32611-7200 (United States); Oomens, Jos; Steill, Jeffrey D. [FOM Institute for Plasma Physics 'Rijnhuizen', Edisonbaan 14, NL-3439MN Nieuwegein (Netherlands)

2011-01-20

96

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

97

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

98

Third-harmonic generation and multiphoton ionization spectroscopy  

SciTech Connect

Nonlinear phenomena, such as multiphoton excitation (MPE) processes leading to ionization and third-harmonic generation (THG) in gases have become the issue of extensive studies over recent years. Studies in rare gases in particular have resulted in several interesting observations in this respect. Thus, it has been established that three-photon resonantly enhanced multiphoton ionization (MPI) in the vicinity of states which are single photon optically coupled to the ground state may occur in efficient competition with THG. The present work demonstrates several new effects which may appear when third-harmonic radiation is present during MPI.

Fotakis, C.; Stockdale, J.A.D.; Proctor, M.J.

1987-01-01

99

High-resolution multimodal clinical multiphoton tomography of skin  

NASA Astrophysics Data System (ADS)

This review focuses on multimodal multiphoton tomography based on near infrared femtosecond lasers. Clinical multiphoton tomographs for 3D high-resolution in vivo imaging have been placed into the market several years ago. The second generation of this Prism-Award winning High-Tech skin imaging tool (MPTflex) was introduced in 2010. The same year, the world's first clinical CARS studies have been performed with a hybrid multimodal multiphoton tomograph. In particular, non-fluorescent lipids and water as well as mitochondrial fluorescent NAD(P)H, fluorescent elastin, keratin, and melanin as well as SHG-active collagen has been imaged with submicron resolution in patients suffering from psoriasis. Further multimodal approaches include the combination of multiphoton tomographs with low-resolution wide-field systems such as ultrasound, optoacoustical, OCT, and dermoscopy systems. Multiphoton tomographs are currently employed in Australia, Japan, the US, and in several European countries for early diagnosis of skin cancer, optimization of treatment strategies, and cosmetic research including long-term testing of sunscreen nanoparticles as well as anti-aging products.

König, Karsten

2011-03-01

100

EXCITATION OF EXTENDED RED EMISSION AND NEAR-INFRARED CONTINUUM RADIATION IN THE INTERSTELLAR MEDIUM  

SciTech Connect

Many small molecules including carbon clusters emit blackbody radiation in the visible spectrum when their internal temperature, T, is raised above 2000 K by photoabsorption. Blackbody emission is known to be the dominant cooling mechanism for small dehydrogenated carbon molecules for 1500 < T < 3000 K. The condition that T > 2000 K would be met by interstellar molecules containing <=28 carbon atoms, heated by energetic photons from the interstellar radiation field. It is shown here that thermal emission will augment photoluminescent emission in extended red emission (ERE) sources when the UV radiation field is enhanced. In particular, this mechanism provides a simple explanation for observations that show that only stars with T {sub eff} > 7000 K excite the ERE. The observation by Witt et al. that photons with energies >10.5 eV are required for the onset of ERE emission can then be interpreted as the condition for the initiation of thermal emission at visible wavelengths. These observational requirements have been combined with laboratory and theoretical data to constrain the emitters of the ERE to dehydrogenated carbon molecules, C {sub N} with 20 <= N <= 28 atoms. The composition and structure of these molecules is discussed and IR band energies for several possible C{sub N} species are provided. These molecules are stable against photodissociation in the interstellar radiation field. It is also shown that dimers of these molecules, (C{sub N} ){sub 2}, may be the species that give rise to the near-infrared continuum first detected by Sellgren. A new effect that might be significant under interstellar conditions involving unimolecular rearrangement reactions in thermally excited molecules is also discussed.

Duley, W. W., E-mail: wwduley@uwaterloo.c [Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1 (Canada)

2009-11-01

101

The impact of pulse duration on multiphoton ionization in the soft X-ray regime  

NASA Astrophysics Data System (ADS)

At the soft X-ray free electron laser FLASH, multiphoton ionization of free atoms has been studied by ion time-of-flight spectroscopy. Depending on the multiphoton mechanism, the ionization processes are influenced in different ways by the FEL pulse duration. This feature has been used, e.g., to measure the pulse duration of FLASH in the femtosecond regime by non-linear autocorrelation. In the present contribution, the impact of pulse duration on multiphoton ionization is discussed with an emphasis on the distinction between sequential and non-sequential processes, and collective electron excitation as well.

Richter, Mathias; Sorokin, Andrey A.; Tiedtke, Kai

2013-05-01

102

Time-Dependent Multiphoton Ionization of Xenon in the Soft-X-Ray Regime  

NASA Astrophysics Data System (ADS)

The time-dependent multiphoton ionization of xenon atoms is studied with femtosecond pulses in the excitation range of the 4d giant resonance at the photon energy of 93 eV. Benefiting from a new operation mode of the free electron laser FLASH, the measurements are performed with varying pulse durations. A strong dependence of the ion charge distribution on the pulse duration allows the different multiphoton mechanisms behind the multiple photoionization of xenon to be disentangled up to a charge state of Xe10+. The results up to Xe8+ are well explained by sequences of single photon, multiphoton, and Auger processes, but higher charge state generation suggests the need for collective electron multiphoton excitations.

Gerken, N.; Klumpp, S.; Sorokin, A. A.; Tiedtke, K.; Richter, M.; Bürk, V.; Mertens, K.; Jurani?, P.; Martins, M.

2014-05-01

103

Transverse correlations in multiphoton entanglement  

SciTech Connect

We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N-photon state. The Klyshko's two-photon advanced-wave picture is generalized to the N-photon case.

Wen Jianming; Rubin, Morton H.; Shih Yanhua [Physics Department, University of Maryland, Baltimore County, Baltimore, Maryland 21250 (United States)

2007-10-15

104

Pulsed infrared radiation excites cultured neonatal spiral and vestibular ganglion neurons by modulating mitochondrial calcium cycling.  

PubMed

Cochlear implants are currently the most effective solution for profound sensorineural hearing loss, and vestibular prostheses are under development to treat bilateral vestibulopathies. Electrical current spread in these neuroprostheses limits channel independence and, in some cases, may impair their performance. In comparison, optical stimuli that are spatially confined may result in a significant functional improvement. Pulsed infrared radiation (IR) has previously been shown to elicit responses in neurons. This study analyzes the response of neonatal rat spiral and vestibular ganglion neurons in vitro to IR (wavelength = 1,863 nm) using Ca(2+) imaging. Both types of neurons responded consistently with robust intracellular Ca(2+) ([Ca(2+)]i) transients that matched the low-frequency IR pulses applied (4 ms, 0.25-1 pps). Radiant exposures of ?637 mJ/cm(2) resulted in continual neuronal activation. Temperature or [Ca(2+)] variations in the media did not alter the IR-evoked transients, ruling out extracellular Ca(2+) involvement or primary mediation by thermal effects on the plasma membrane. While blockage of Na(+), K(+), and Ca(2+) plasma membrane channels did not alter the IR-evoked response, blocking of mitochondrial Ca(2+) cycling with CGP-37157 or ruthenium red reversibly inhibited the IR-evoked [Ca(2+)]i transients. Additionally, the magnitude of the IR-evoked transients was dependent on ryanodine and cyclopiazonic acid-dependent Ca(2+) release. These results suggest that IR modulation of intracellular calcium cycling contributes to stimulation of spiral and vestibular ganglion neurons. As a whole, the results suggest selective excitation of neurons in the IR beam path and the potential of IR stimulation in future auditory and vestibular prostheses. PMID:24920028

Lumbreras, Vicente; Bas, Esperanza; Gupta, Chhavi; Rajguru, Suhrud M

2014-09-15

105

Nanosecond simulations of the dynamics of C60 excited by intense near-infrared laser pulses: impulsive Raman excitation, rearrangement, and fragmentation.  

PubMed

Impulsive Raman excitation of C(60) by single or double pulses of near-infrared wavelength ? = 1800 nm was investigated by using a time-dependent adiabatic state approach combined with the density functional theory method. We confirmed that the vibrational energy stored in a Raman active mode of C(60) is maximized when T(p) ~ T(vib)/2 in the case of a single pulse, where T(p) is the pulse length and T(vib) is the vibrational period of the mode. In the case of a double pulse, mode selective excitation can be achieved by adjusting the pulse interval ?. The energy of a Raman active mode is maximized if ? is chosen to equal an integer multiple of T(vib) and it is minimized if ? is equal to a half-integer multiple of T(vib). We also investigated the subsequent picosecond or nanosecond dynamics of Stone-Wales rearrangement (SWR) and fragmentation by using the density-functional based tight-binding semiempirical method. We present how SWRs are caused by the flow of vibrational kinetic energy on the carbon bond network of C(60). In the case where the h(g)(1) prolate-oblate mode is initially excited, the number of SWRs before fragmentation is larger than in the case of a(g)(1) mode excitation for the same excess vibrational energy. Fragmentation by C(2) ejection C(60) ? C(58) + C(2) is found to occur from strained, fused pentagon/pentagon defects produced by a preceding SWR, which confirms the earliest mechanistic speculations of Smalley et al. [J. Chem. Phys. 88, 220 (1988)]. The fragmentation rate of C(2) ejection in the case of h(g)(1) mode excitation does not follow a statistical description as employed for instance in the Rice-Ramsperger-Kassel (RRK) theory, whereas the rate for a(g)(1) mode excitation does follow the prediction by RRK. We also found for the h(g)(1) mode excitation that the nonstatistical nature affects the distribution of barycentric velocities of fragments C(58) and C(2). This result suggests that it is possible to control rearrangement and subsequent bond breaking in a "nonstatistical" way by initial selective mode excitation. PMID:22559479

Niitsu, Naoyuki; Kikuchi, Miyu; Ikeda, Hayato; Yamazaki, Kaoru; Kanno, Manabu; Kono, Hirohiko; Mitsuke, Koichiro; Toda, Mikito; Nakai, Katsunori

2012-04-28

106

Nanosecond simulations of the dynamics of C60 excited by intense near-infrared laser pulses: Impulsive Raman excitation, rearrangement, and fragmentation  

NASA Astrophysics Data System (ADS)

Impulsive Raman excitation of C60 by single or double pulses of near-infrared wavelength ? = 1800 nm was investigated by using a time-dependent adiabatic state approach combined with the density functional theory method. We confirmed that the vibrational energy stored in a Raman active mode of C60 is maximized when Tp ~ Tvib/2 in the case of a single pulse, where Tp is the pulse length and Tvib is the vibrational period of the mode. In the case of a double pulse, mode selective excitation can be achieved by adjusting the pulse interval ?. The energy of a Raman active mode is maximized if ? is chosen to equal an integer multiple of Tvib and it is minimized if ? is equal to a half-integer multiple of Tvib. We also investigated the subsequent picosecond or nanosecond dynamics of Stone-Wales rearrangement (SWR) and fragmentation by using the density-functional based tight-binding semiempirical method. We present how SWRs are caused by the flow of vibrational kinetic energy on the carbon bond network of C60. In the case where the hg(1) prolate-oblate mode is initially excited, the number of SWRs before fragmentation is larger than in the case of ag(1) mode excitation for the same excess vibrational energy. Fragmentation by C2 ejection C60 --> C58 + C2 is found to occur from strained, fused pentagon/pentagon defects produced by a preceding SWR, which confirms the earliest mechanistic speculations of Smalley et al. [J. Chem. Phys. 88, 220 (1988)]. The fragmentation rate of C2 ejection in the case of hg(1) mode excitation does not follow a statistical description as employed for instance in the Rice-Ramsperger-Kassel (RRK) theory, whereas the rate for ag(1) mode excitation does follow the prediction by RRK. We also found for the hg(1) mode excitation that the nonstatistical nature affects the distribution of barycentric velocities of fragments C58 and C2. This result suggests that it is possible to control rearrangement and subsequent bond breaking in a ``nonstatistical'' way by initial selective mode excitation.

Niitsu, Naoyuki; Kikuchi, Miyu; Ikeda, Hayato; Yamazaki, Kaoru; Kanno, Manabu; Kono, Hirohiko; Mitsuke, Koichiro; Toda, Mikito; Nakai, Katsunori

2012-04-01

107

Supersonic jet/multiphoton ionization spectrometry of chemical species resulting from thermal decomposition and laser ablation of polymers  

SciTech Connect

The chemical species resulting from thermal decomposition and laser ablation of polymers are measured by excitation/fluorescence and multiphoton ionization/mass spectrometries after supersonic jet expansion for rotational cooling to simply the optical spectrum. The signal of minor chemical species occurred is strongly enhanced by resonant excitation and multiphoton ionization, and even the isomer can be clearly differentiated. For example, p-cresol occurred by thermal decomposition of polycarbonate is detected selectively by mass-selected resonant multiphoton ionization spectrometry. Various chemical species occurred by laser ablation of even a polystyrene foam are also measured by this technique.

Hozumi, Masami; Murata, Yoshiaki; Cheng-Huang Lin; Imasaka, Totaro [Department of Chemical Science and Technology, Faculty of Engineering, Hakozaki, Higashi-Ku, Fukuoka 812 (Japan)

1995-04-01

108

Developing compact multiphoton systems using femtosecond fiber lasers.  

PubMed

We implement a fiber-delivered compact femtosecond fiber laser at 1,030-nm wavelength in multiphoton imaging. The laser pulse duration is 150 fs, the average power is 200 mW, and the repetition rate is 40 MHz. The laser measures 200 x 160 x 45 mm in size and its output is delivered through a photonic bandgap fiber. Intrinsic second-harmonic generation signal is excited from rat tail tendon and human skin samples. Two-photon excited fluorescence signal is obtained from human skin tissues stained with exogenous fluorophore. Our results show that femtosecond fiber lasers at 1030-nm wavelength have significant potential in developing compact, all-fiber-based, portable multiphoton systems and endoscopes. PMID:19566289

Tang, Shuo; Liu, Jian; Krasieva, Tatiana B; Chen, Zhongping; Tromberg, Bruce J

2009-01-01

109

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

110

Development of an applicator for multiphoton PDT  

NASA Astrophysics Data System (ADS)

Multiphoton excitation of photosensitizers for laser induced fluorescence diagnosis (LIFD) and photodynamic therapy (PDT) of tumors has the advantage of greater tissue penetration due to the longer wavelength of irradiation. However, multiphoton LIFD and PDT are presently not clinically applicable as there are no applicators available for the delivery of the pulsed laser radiation to the operating room. As an approach, in this contribution the beam delivery through photonic crystal fibers has been investigated. Pulses of a Ti:sapphire laser of 100 fs pulse duration and an average power of 150 mW have been transported through such a fiber of 25 m length and the resulting pulses show the absence of nonlinear contributions but still a broadening of the pulse to 2 ps due to the dispersion of the fiber. It is planned to compensate this broadening by a grating in front of the fiber. Alternatively, the transport of laser radiation of 150 fs and 100 mW through a mirror-joint-arm used for conventional CO2 lasers has been tested showing no broadening of the laser pulses. Two-photon photodynamic activity of mTHPC-CMPEG4 shall serve as a test of the laser light transport system.

Graschew, Georgi; Bastian, Matthias; Rakowsky, Stefan; Roelofs, Theo A.; Balanos, Evangelos; Schlag, Peter M.; Steinmeyer, Gunter; Elsaesser, Thomas

2004-09-01

111

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

112

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

113

Multimodal multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is a powerful technique for high spatial resolution thick tissue imaging. In its simple version, it uses a high repetition rate femtosecond oscillator laser source focussed and scanned across biological sample that contains fluorophores. However, not every biological structure is inherently fluorescent or can be stained without causing biochemical changes. To circumvent these limitations, other non-invasive nonlinear optical imaging approaches are currently being developed and investigated with regard to different applications. These techniques are: (1) second harmonic generation (SHG), (2) third harmonic generation (THG), and (3) coherent anti-Stokes Raman scattering (CARS) microscopy. The main advantage of the above mentioned techniques is that they derive their imaging contrast from optical nonlinearities that do not involve fluorescence process. As a particular application example we investigated collagen arrays. We show that combining SHG-THG-CARS onto a single imaging platform provides complementary information about the sub-micron architecture of the tissue. SHG microscopy reveals the fibrillar architecture of collagen arrays and confirm a rather high degree of heterogeneity of ?(2) within the focal volume, THG highlights the boundaries between the collagen sheets, and CH2 spectroscopic contrast with CARS.

Légaré, François; Pfeffer, Christian P.; Ganikhanov, Feruz

2009-02-01

114

Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy  

PubMed Central

We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences. PMID:19725639

Carriles, Ramon; Schafer, Dawn N.; Sheetz, Kraig E.; Field, Jeffrey J.; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W.; Squier, Jeffrey A.

2009-01-01

115

Invited review article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy.  

PubMed

We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences. PMID:19725639

Carriles, Ramón; Schafer, Dawn N; Sheetz, Kraig E; Field, Jeffrey J; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W; Squier, Jeffrey A

2009-08-01

116

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

PubMed

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

2012-07-01

117

Near-infrared emitting ytterbium metal-organic frameworks with tunable excitation properties.  

PubMed

The design of metal-organic frameworks (MOFs) incorporating near-infrared emitting ytterbium cations and organic sensitizers allows for the preparation of new materials with tunable and enhanced photophysical properties. PMID:19617965

White, Kiley A; Chengelis, Demetra A; Zeller, Matthias; Geib, Steven J; Szakos, Jessica; Petoud, Stéphane; Rosi, Nathaniel L

2009-08-14

118

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

119

Mitigating Phototoxicity during Multiphoton Microscopy of Live Drosophila Embryos in the 1.0–1.2 µm Wavelength Range  

PubMed Central

Light-induced toxicity is a fundamental bottleneck in microscopic imaging of live embryos. In this article, after a review of photodamage mechanisms in cells and tissues, we assess photo-perturbation under illumination conditions relevant for point-scanning multiphoton imaging of live Drosophila embryos. We use third-harmonic generation (THG) imaging of developmental processes in embryos excited by pulsed near-infrared light in the 1.0–1.2 µm range. We study the influence of imaging rate, wavelength, and pulse duration on the short-term and long-term perturbation of development and define criteria for safe imaging. We show that under illumination conditions typical for multiphoton imaging, photodamage in this system arises through 2- and/or 3-photon absorption processes and in a cumulative manner. Based on this analysis, we derive general guidelines for improving the signal-to-damage ratio in two-photon (2PEF/SHG) or THG imaging by adjusting the pulse duration and/or the imaging rate. Finally, we report label-free time-lapse 3D THG imaging of gastrulating Drosophila embryos with sampling appropriate for the visualisation of morphogenetic movements in wild-type and mutant embryos, and long-term multiharmonic (THG-SHG) imaging of development until hatching. PMID:25111506

Débarre, Delphine; Olivier, Nicolas; Supatto, Willy; Beaurepaire, Emmanuel

2014-01-01

120

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

121

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

PubMed

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(1) state. By applying the new IR/UV/IR/UV technique, we are able to show experimentally that both in the electronic ground (S(0)) and the electronically excited state (S(1)) two isomers have to be assigned. PMID:22443757

Weiler, M; Bartl, K; Gerhards, M

2012-03-21

122

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

NASA Astrophysics Data System (ADS)

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 S1 state. By applying the new IR/UV/IR/UV technique, we are able to show experimentally that both in the electronic ground (S0) and the electronically excited state (S1) two isomers have to be assigned.

Weiler, M.; Bartl, K.; Gerhards, M.

2012-03-01

123

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

124

The layered resolved microstructure and spectroscopy of mouse oral mucosa using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

The layered-resolved microstructure and spectroscopy of mouse oral mucosa are obtained using a combination of multiphoton imaging and spectral analysis with different excitation wavelengths. In the keratinizing layer, the keratinocytes microstructure can be characterized and the keratinizing thickness can be measured. The keratin fluorescence signal can be further characterized by emission maxima at 510 nm. In the epithelium, the cellular microstructure can be quantitatively visualized with depth and the epithelium thickness can be determined by multiphoton imaging excited at 730 nm. The study also shows that the epithelial spectra excited at 810 nm, showing a combination of NADH and FAD fluorescence, can be used for the estimation of the metabolic state in epithelium. Interestingly, a second-harmonic generation (SHG) signal from DNA was observed for the first time within the epithelial layer in backscattering geometry and provides the possibility of analyzing the chromatin structure. In the stroma, the combination of multiphoton imaging and spectral analysis excited at 850 nm in tandem can obtain quantitative information regarding the biomorphology and biochemistry of stroma. Specifically, the microstructure of collagen, minor salivary glands and elastic fibers, and the optical property of the stroma can be quantitatively displayed. Overall, these results suggest that the combination of multiphoton imaging and spectral analysis with different excitation wavelengths has the potential to provide important and comprehensive information for early diagnosis of oral cancer.

Zhuo, Shuangmu; Chen, Jianxin; Jiang, Xingshan; Xie, Shusen; Chen, Rong; Cao, Ning; Zou, Qilian; Xiong, Shuyuan

2007-08-01

125

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

126

Simultaneous time and wavelength resolved spectroscopy under two-colour near infrared and terahertz excitation.  

PubMed

Time and wavelength resolved spectroscopy requires optical sources emitting very short pulses and a fast detection mechanism capable of measuring the evolution of the output spectrum as a function of time. We use table-top Ti:sapphire lasers and a free-electron laser (FEL) emitting ps pulses as excitation sources and a streak camera coupled to a spectrometer for detection. One of the major aspects of this setup is the synchronization of pulses from the two lasers which we describe in detail. Optical properties of the FEL pulses are studied by autocorrelation and electro-optic sampling measurements. We discuss the advantages of using this setup to perform photoluminescence quenching in semiconductor quantum wells and quantum dots. Carrier redistribution due to pulsed excitation in these heterostructures can be investigated directly. Sideband generation in quantum wells is also studied where the intense FEL pulses facilitate the detection of the otherwise weak nonlinear effect. PMID:22047280

Bhattacharyya, J; Wagner, M; Zybell, S; Winnerl, S; Stehr, D; Helm, M; Schneider, H

2011-10-01

127

Near-infrared long-slit spectra of Seyfert galaxies: gas excitation across the central kiloparsec  

NASA Astrophysics Data System (ADS)

Context. The excitation of the gas phase of the interstellar medium can be driven by various mechanisms. In galaxies with an active nucleus, such as Seyfert galaxies, both radiative and mechanical energy from the central black hole, or the stars in the disk surrounding it may play a role. Aims: We investigate the relative importance and range of influence of the active galactic nucleus for the excitation of ionized and molecular gas in the central kiloparsec of its host galaxy. Methods: We present H- and K-band long-slit spectra for a sample of 21 nearby (D < 70 Mpc) Seyfert galaxies obtained with the NIRSPEC instrument on the Keck telescope. For each galaxy, we fit the nebular line emission, stellar continua, and warm molecular gas as a function of distance from the nucleus. Results: Our analysis does not reveal a clear difference between the nucleus proper and off-nuclear environment in terms of excitation mechanisms, suggesting that the influence of an AGN reaches far into the disk of the host galaxy. The radial variations in emission line ratios indicate that, while local mechanisms do affect the gas excitation, they are often averaged out when measuring over extended regions. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.Table 4 and Appendix A are available in electronic form at http://www.aanda.orgThe fully calibrated long-slit spectra and fitting are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/560/A99

van der Laan, T. P. R.; Schinnerer, E.; Böker, T.; Armus, L.

2013-12-01

128

Near infrared two-photon excitation cross-sections of voltage-sensitive dyes.  

PubMed

Microscopy based on voltage-sensitive dyes has proven effective for revealing spatio-temporal patterns of neuronal activity in vivo and in vitro. Two-photon microscopy using voltage-sensitive dyes offers the possibility of wide-field visualization of membrane potential on sub-cellular length scales, hundreds of microns below the tissue surface. Very little information is available, however, about the utility of voltage-sensitive dyes for two-photon imaging purposes. Here we report on measurements of two-photon fluorescence excitation cross-sections for nine voltage-sensitive dyes in a solvent, octanol, intended to simulate the membrane environment. Ultrashort light pulses from a Ti:sapphire laser were used for excitation from 790 to 960 nm, and fluorescein dye was used as a calibration standard. Overall, dyes RH795, RH421, RH414, di-8-ANEPPS, and di-8-ANEPPDHQ had the largest two-photon excitation cross-sections ( approximately 15 x 10(-50)cm4 s photon(-1)) in this wavelength region and are therefore potentially useful for two-photon microscopy. Interestingly, di-8-ANEPPDHQ, a chimera constructed from the potentiometric dyes RH795 and di-8-ANEPPS, exhibited larger cross-sections than either of its constituents. PMID:16129493

Fisher, Jonathan A N; Salzberg, Brian M; Yodh, Arjun G

2005-10-15

129

Multiphoton imaging and quantification of tissue glycation  

NASA Astrophysics Data System (ADS)

In this work, we applied multi-photon microscopy to image and characterize the extent of tissue glycation. Specifically, features of multi-photon autofluorescence (MPAF) and second harmonic generation (SHG) images were presented. Our study shows that multiphoton imaging is capable of providing qualitative and quantitative information of the extent of tissue glycation in ribose treated samples including bovine sclera and vessel and that this approach may be useful for clinical evaluation of advanced glycation endproducts (AGEs) formation.

Ghazaryan, Ara A.; Tseng, Jo-Ya; Lo, Wen; Chen, Yang-Fang; Hovhannisyan, Vladimir; Chen, Shean-Jen; Tan, Hsin-Yuan; Dong, Chen-Yuan

2011-03-01

130

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

131

Measurement of molecular diffusion in solution by multiphoton fluorescence photobleaching recovery  

PubMed Central

Multiphoton fluorescence photobleaching recovery (MP-FPR) is a technique for measuring the three-dimensional (3D) mobility of fluorescent molecules with 3D spatial resolution of a few microns. A brief, intense flash of mode-locked laser light pulses excites fluorescent molecules via multiphoton excitation in an ellipsoidal focal volume and photobleaches a fraction. Because multiphoton excitation of fluorophores is intrinsically confined to the high-intensity focal volume of the illuminating beam, the bleached region is restricted to a known, three-dimensionally defined volume. Fluorescence in this focal volume is measured with multiphoton excitation, using the attenuated laser beam to measure fluorescence recovery as fresh unbleached dye diffuses in. The time course of the fluorescence recovery signal after photobleaching can be analyzed to determine the diffusion coefficient of the fluorescent species. The mathematical formulas used to fit MP-FPR recovery curves and the techniques needed to properly utilize them to acquire the diffusion coefficients of fluorescently labeled molecules within cells are presented here. MP-FPR is demonstrated on calcein in RBL-2H3 cells, using an anomalous subdiffusion model, as well as in aqueous solutions of wild-type green fluorescent protein, yielding a diffusion coefficient of 8.7 x 10(-7) cm(2)s(-1) in excellent agreement with the results of other techniques. PMID:10545381

Brown, EB; Wu, ES; Zipfel, W; Webb, WW

1999-01-01

132

Differentiation of normal and cancerous lung tissues by multiphoton imaging  

NASA Astrophysics Data System (ADS)

In this work, we utilized multiphoton microscopy for the label-free diagnosis of non-cancerous, lung adenocarcinoma (LAC), and lung squamous cell carcinoma (SCC) tissues from human. Our results show that the combination of second harmonic generation (SHG) and multiphoton excited autofluorescence (MAF) signals may be used to acquire morphological and quantitative information in discriminating cancerous from non-cancerous lung tissues. Specifically, non-cancerous lung tissues are largely fibrotic in structure while cancerous specimens are composed primarily of tumor masses. Quantitative ratiometric analysis using MAF to SHG index (MAFSI or SAAID) shows that the average MAFSI for noncancerous and LAC lung tissue pairs are 0.55 +/-0.23 and 0.87+/-0.15 respectively. In comparison, the MAFSIs for the noncancerous and SCC tissue pairs are 0.50+/-0.12 and 0.72+/-0.13 respectively. Intrinsic fluorescence ratio (FAD/NADH) of SCC and non-cancerous tissues are 0.40+/-0.05 and 0.53+/-0.05 respectively, the redox ratio of SCC diminishes significantly, indicating that increased cellular metabolic activity. Our study shows that nonlinear optical microscopy can assist in differentiating and diagnosing pulmonary cancer from non-cancerous tissues. With additional development, multiphoton microscopy may be used for the clinical diagnosis of lung cancers.

Wang, Chun-Chin; Li, Feng-Chieh; Wu, Ruei-Jr; Hovhannisyan, Vladimir A.; Lin, Wei-Chou; Lin, Sung-Jan; So, Peter T. C.; Dong, Chen-Yuan

2010-02-01

133

Infrared nanospectroscopy and imaging of collective superfluid excitations in anisotropic superconductors  

NASA Astrophysics Data System (ADS)

We investigate near-field infrared spectroscopy and superfluid polariton imaging experiments on conventional and unconventional superconductors. Our modeling shows that near-field spectroscopy can measure the magnitude of the superconducting energy gap in Bardeen-Cooper-Schrieffer-like superconductors with nanoscale spatial resolution. We demonstrate how the same technique can measure the c-axis plasma frequency, and thus the c-axis superfluid density, of layered unconventional superconductors with a similar spatial resolution. Our modeling also shows that near-field techniques can image superfluid surface mode interference patterns near physical and electronic boundaries. We describe how these images can be used to extract the collective mode dispersion of anisotropic superconductors with subdiffractional spatial resolution.

Stinson, H. T.; Wu, J. S.; Jiang, B. Y.; Fei, Z.; Rodin, A. S.; Chapler, B. C.; McLeod, A. S.; Castro Neto, A.; Lee, Y. S.; Fogler, M. M.; Basov, D. N.

2014-07-01

134

Raman scattering and plasmonic photocatalysis of single particles of NaYF4:Yb,Er@Ag under near-infrared laser excitation.  

PubMed

This study has investigated the plasmonic photocatalytic ability of silver nanoparticles (Ag NPs) and the significantly improved Raman achieved by decorating them on a single NaYF4:Yb,Er upconversion (UC) microcrystal under near-infrared excitation. This points to new applications for UC-noble metal composites and promises a novel method for constructing SERS-active nanostructures. PMID:25267978

Ma, Yongmei; Liu, Honglin; Han, Zhenzhen; Yang, Liangbao; Sun, Bai; Liu, Jinhuai

2014-10-15

135

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

136

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

137

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

138

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

139

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

140

COLLISIONAL EXCITATION OF FAR-INFRARED LINE EMISSIONS FROM WARM INTERSTELLAR CARBON MONOXIDE (CO)  

SciTech Connect

Motivated by recent observations with Herschel/PACS, and the availability of new rate coefficients for the collisional excitation of CO, the excitation of warm astrophysical CO is revisited with the use of numerical and analytic methods. For the case of an isothermal medium, results have been obtained for a wide range of gas temperatures (100-5000 K) and H{sub 2} densities (10{sup 3}-10{sup 9} cm{sup -3}), and presented in the form of rotational diagrams, in which the logarithm of the column density per magnetic substate, log (N{sub J} /g{sub J} ), is plotted for each state, as a function of its energy, E{sub J} . For rotational transitions in the wavelength range accessible to Herschel/PACS, such diagrams are nearly linear when n(H{sub 2}) {>=} 10{sup 8} cm{sup -3}. When n(H{sub 2}) {approx} 10{sup 6.8}-10{sup 8} cm{sup -3}, they exhibit significant negative curvature, whereas when n(H{sub 2}) {<=} 10{sup 4.8} cm{sup -3}, the curvature is uniformly positive throughout the PACS-accessible range. Thus, the observation of a positively curved CO rotational diagram does not necessarily require the presence of multiple temperature components. Indeed, for some sources observed with Herschel/PACS, the CO rotational diagrams show a modest positive curvature that can be explained by a single isothermal component. Typically, the required physical parameters are densities in the 10{sup 4}-10{sup 5} cm{sup -3} range and temperatures close to the maximum at which CO can survive. Other sources exhibit rotational diagrams with more curvature than can be accounted for by a single temperature component. For the case of a medium with a power-law distribution of gas temperatures, dN/dT{proportional_to}T{sup -b}, results have been obtained for H{sub 2} densities 10{sup 3}-10{sup 9} cm{sup -3} and power-law indices, b, in the range 1-5; such a medium can account for a CO rotational diagram that is more positively curved than any resulting from an isothermal medium.

Neufeld, David A. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)

2012-04-20

141

Wavefront sensorless adaptive optics temporal focusing-based multiphoton microscopy.  

PubMed

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

2014-06-01

142

Near-infrared-excited confocal Raman spectroscopy advances in vivo diagnosis of cervical precancer  

NASA Astrophysics Data System (ADS)

Raman spectroscopy is a unique optical technique that can probe the changes of vibrational modes of biomolecules associated with tissue premalignant transformation. This study evaluates the clinical utility of confocal Raman spectroscopy over near-infrared (NIR) autofluorescence (AF) spectroscopy and composite NIR AF/Raman spectroscopy for improving early diagnosis of cervical precancer in vivo at colposcopy. A rapid NIR Raman system coupled with a ball-lens fiber-optic confocal Raman probe was utilized for in vivo NIR AF/Raman spectral measurements of the cervix. A total of 1240 in vivo Raman spectra [normal (n=993), dysplasia (n=247)] were acquired from 84 cervical patients. Principal components analysis (PCA) and linear discriminant analysis (LDA) together with a leave-one-patient-out, cross-validation method were used to extract the diagnostic information associated with distinctive spectroscopic modalities. The diagnostic ability of confocal Raman spectroscopy was evaluated using the PCA-LDA model developed from the significant principal components (PCs) [i.e., PC4, 0.0023% PC5, 0.00095% PC8, 0.00022%, (p<0.05)], representing the primary tissue Raman features (e.g., 854, 937, 1095, 1253, 1311, 1445, and 1654 cm-1). Confocal Raman spectroscopy coupled with PCA-LDA modeling yielded the diagnostic accuracy of 84.1% (a sensitivity of 81.0% and a specificity of 87.1%) for in vivo discrimination of dysplastic cervix. The receiver operating characteristic curves further confirmed that the best classification was achieved using confocal Raman spectroscopy compared to the composite NIR AF/Raman spectroscopy or NIR AF spectroscopy alone. This study illustrates that confocal Raman spectroscopy has great potential to improve early diagnosis of cervical precancer in vivo during clinical colposcopy.

Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J. H.; Ilancheran, Arunachalam; Huang, Zhiwei

2013-06-01

143

Infrared and ultraviolet laser spectroscopy of jet-cooled substituted salicylic acids; substitution effects on the excited state intramolecular proton transfer in salicylic acid  

NASA Astrophysics Data System (ADS)

Substitution effects on the excited state intramolecular proton transfer (ESIPT) in the salicylic acid (SA) frame were studied by electronic and infrared spectroscopy of jet-cooled 5-methoxylsalicylic acid (5-MeOSA), 5-methylsalicylic acid (5-MeSA), 5-fluorosalicylic acid (5-FSA), 6-fluorosalicylic acid (6-FSA), and methyl salicylate (MS). Infrared spectra were measured in the 3 µm region for both the electronic ground (S0) and first excited (S1) states. The electronic excitation/emission spectra of 5-MeSA and 6-FSA showed the typical spectral features of ESIPT, which have been found in the spectra of SA. On the other hand, 5-MeOSA and 5-FSA exhibit a mirror-image relation between their excitation and emission spectra, which has been regarded as a result of the suppression of ESIPT. Despite such a remarkable difference among the electronic spectra, IR spectroscopy shows that a drastic change of the phenolic OH stretching vibration does occur upon electronic excitation of all substituted SAs, that is, the phenolic OH band of all the SAs disappears from the 3 µm region, indicating a large elongation of the phenolic O-H bond (over 0.1 Å) in S1. This result means that the intramolecular hydrogen bond strength is remarkably enhanced by electronic excitation in all the substituted SAs. Substitution effects on ESIPT in dimers are also discussed.

Abd El-Hakam Abou El-Nasr, E.; Fujii, A.; Ebata, T.; Mikami, N.

144

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

145

Warm Molecular Gas in M51: Mapping the Excitation Temperature and Mass of H_2 with the Spitzer Infrared Spectrograph  

E-print Network

We have mapped the warm molecular gas traced by the H_2 S(0) - H_2 S(5) pure rotational mid-infrared emission lines over a radial strip across the nucleus and disk of M51 (NGC 5194) using the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. The six H_2 lines have markedly different emission distributions. We obtained the H_2 temperature and surface density distributions by assuming a two temperature model: a warm (T = 100 - 300 K) phase traced by the low J (S(0) - S(2)) lines and a hot phase (T = 400 - 1000 K) traced by the high J (S(2) - S(5)) lines. The lowest molecular gas temperatures are found within the spiral arms (T ~ 155 K), while the highest temperatures are found in the inter-arm regions (T > 700 K). The warm gas surface density reaches a maximum of 11 M_sun/pc^2 in the northwestern spiral arm, whereas the hot gas surface density peaks at 0.24 M_sun/pc^2 at the nucleus. The spatial offset between the peaks in the warm and hot phases and the differences in the distributions of the H_2 line emission suggest that the warm phase is mostly produced by UV photons in star forming regions while the hot phase is mostly produced by shocks or X-rays associated with nuclear activity. The warm H_2 is found in the dust lanes of M51, spatially offset from the brightest HII regions. The warm H_2 is generally spatially coincident with the cold molecular gas traced by CO (J = 1 - 0) emission, consistent with excitation of the warm phase in dense photodissociation regions (PDRs). In contrast, the hot H_2 is most prominent in the nuclear region. Here, over a 0.5 kpc radius around the nucleus of M51, the hot H_2 coincides with [O IV](25.89 micron) and X-ray emission indicating that shocks and/or X-rays are responsible for exciting this phase.

G. Brunner; K. Sheth; L. Armus; M. Wolfire; S. Vogel; E. Schinnerer; G. Helou; R. Dufour; J. Smith; D. Dale

2007-11-30

146

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

147

Visualizing the podocyte with multiphoton microscopy  

PubMed Central

The podocyte is a highly specialized kidney glomerular epithelial cell that plays an essential role in glomerular filtration and is believed to be the target of numerous glomerular diseases leading to proteinuria. Despite the leaps in our understanding of podocyte biology, new methodologies are needed to facilitate research into the cell. Multiphoton microscopy (MPM) was used to image the nephrin knockout/green fluorescent protein (GFP) knock-in heterozygote (Nphs1tm1Rkl/J) mouse. The nephrin promoter restricts GFP expression to the podocytes that fluoresce green under excitation. From the exterior of an intact kidney, MPM can peer into the renal parenchyma and visualize the podocytes that outline the globular shape of the glomeruli. Details as fine as the podocyte’s secondary processes can be resolved. In contrast, podocytes exhibit no fluorescence in the wildtype mouse and are invisible to MPM. Phenotypically, there are no significant differences between wildtype and Nphs1tm1Rkl/J mice in body weight, urinary albumin excretion, creatinine clearance, or glomerular depth. Interestingly, the glomeruli are closer to the kidney capsule in female mice, making the gender the preferred choice for MPM. For the first time, green fluorescent podocytes in a mouse model free of confounding phenotypes can be visualized unequivocally and in the “positive” by MPM, facilitating intravital studies of the podocyte. PMID:23022193

Khoury, Charbel C.; Khayat, Mark F.; Yeo, Tet-Kin; Pyagay, Petr E.; Wang, Amy; Asuncion, Allan M.; Sharma, Kumar; Yu, Weiming; Chen, Sheldon

2012-01-01

148

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

149

Picosecond near-infrared excited transient Raman spectra of ?-carotene in the excited S 2 state: Solvent effects on the in-phase C dbnd C stretching band and vibronic coupling  

NASA Astrophysics Data System (ADS)

Picosecond time-resolved Raman spectra of ?-carotene in the excited S 2 ( 1Bu+) state have been obtained in resonance with its near-infrared transient absorption. The Raman band due to the in-phase C dbnd C stretching mode of ?-carotene in the S 2 state has been observed at about 1550 cm -1. The solvent effects on this band are discussed in comparison with the previous results on the corresponding bands in the ground S 0 ( 1Ag-) state and the excited S 1 ( 2Ag-) state.

Sakamoto, Akira; Matsuno, Shinya; Tasumi, Mitsuo

2010-07-01

150

Gas-Phase Infrared Spectrum of the Coronene Cation  

NASA Astrophysics Data System (ADS)

The gas-phase infrared spectrum of the coronene cation in the 700-1700 cm-1 range is presented. The spectrum is obtained via multiphoton dissociation spectroscopy of ionic coronene stored in a quadrupole ion trap using the intense and narrowband infrared radiation of a free electron laser. The spectrum shows main absorption peaks at 849, 1327, and 1533 cm-1 along with some weak and barely resolved features, in good agreement with density functional calculations if the effects of vibrational anharmonicity are accounted for. Relative line intensities show remarkable differences with respect to matrix isolation data. The novel experimental technique applied here leads in a natural way to an absorption spectrum of highly excited species. Hence, measured absorption spectra can be compared rather directly to interstellar emission spectra, negating to some extent the need for detailed model calculations.

Oomens, Jos; Sartakov, Boris G.; Tielens, A. G. G. M.; Meijer, Gerard; von Helden, Gert

2001-10-01

151

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

152

Resonant enhanced multiphoton ionization studies of atomic oxygen  

NASA Technical Reports Server (NTRS)

In resonant enhanced multiphoton ionization (REMPI), an atom absorbs several photons making a transition to a resonant intermediate state and subsequently ionizing out of it. With currently available tunable narrow-band lasers, the extreme sensitivity of REMPI to the specific arrangement of levels can be used to selectively probe minute amounts of a single species (atom) in a host of background material. Determination of the number density of atoms from the observed REMPI signal requires a knowledge of the multiphoton ionization cross sections. The REMPI of atomic oxygen was investigated through various excitation schemes that are feasible with available light sources. Using quantum defect theory (QDT) to estimate the various atomic parameters, the REMPI dynamics in atomic oxygen were studied incorporating the effects of saturation and a.c. Stark shifts. Results are presented for REMPI probabilities for excitation through various 2p(3) (4S sup o) np(3)P and 2p(3) (4S sup o) nf(3)F levels.

Dixit, S. N.; Levin, D.; Mckoy, V.

1987-01-01

153

Cell-based and in vivo spectral analysis of fluorescent proteins for multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy of cells and subcellular structures labeled with fluorescent proteins is the state-of-the-art technology for longitudinal imaging studies in tissues and living animals. Successful analysis of separate cell populations or signaling events by intravital microscopy requires optimal pairing of multiphoton excitation wavelengths with spectrally distinct fluorescent proteins. While prior studies have analyzed two photon absorption properties of isolated fluorescent proteins, there is limited information about two photon excitation and fluorescence emission profiles of fluorescent proteins expressed in living cells and intact tissues. Multiphoton microscopy was used to analyze fluorescence outputs of multiple blue, green, and red fluorescent proteins in cultured cells and orthotopic tumor xenografts of human breast cancer cells. It is shown that commonly used orange and red fluorescent proteins are excited efficiently by 750 to 760 nm laser light in living cells, enabling dual color imaging studies with blue or cyan proteins without changing excitation wavelength. It is also shown that small incremental changes in excitation wavelength significantly affect emission intensities from fluorescent proteins, which can be used to optimize multi-color imaging using a single laser wavelength. These data will direct optimal selection of fluorescent proteins for multispectral two photon microscopy.

Salomonnson, Emma; Mihalko, Laura Anne; Verkhusha, Vladislav V.; Luker, Kathryn E.; Luker, Gary D.

2012-09-01

154

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

155

MULTI-PHOTON PHOSPHOR FEASIBILITY RESEARCH  

SciTech Connect

Development of multi-photon phosphor materials for discharge lamps represents a goal that would achieve up to a doubling of discharge (fluorescent) lamp efficacy. This report reviews the existing literature on multi-photon phosphors, identifies obstacles in developing such phosphors, and recommends directions for future research to address these obstacles. To critically examine issues involved in developing a multi-photon phosphor, the project brought together a team of experts from universities, national laboratories, and an industrial lamp manufacturer. Results and findings are organized into three categories: (1) Multi-Photon Systems and Processes, (2) Chemistry and Materials Issues, and (3) Concepts and Models. Multi-Photon Systems and Processes: This category focuses on how to use our current understanding of multi-photon phosphor systems to design new phosphor systems for application in fluorescent lamps. The quickest way to develop multi-photon lamp phosphors lies in finding sensitizer ions for Gd{sup 3+} and identifying activator ions to red shift the blue emission from Pr{sup 3+} due to the {sup 1}S{sub 0} {yields} {sup 1}I{sub 6} transition associated with the first cascading step. Success in either of these developments would lead to more efficient fluorescent lamps. Chemistry and Materials Issues: The most promising multi-photon phosphors are found in fluoride hosts. However, stability of fluorides in environments typically found in fluorescent lamps needs to be greatly improved. Experimental investigation of fluorides in actual lamp environments needs to be undertaken while working on oxide and oxyfluoride alternative systems for backup. Concepts and Models: Successful design of a multi-photon phosphor system based on cascading transitions of Gd{sup 3+} and Pr{sup 3+} depends critically on how the former can be sensitized and the latter can sensitize an activator ion. Methods to predict energy level diagrams and Judd-Ofelt parameters of multi-photon transitions are needed to help guide the experimental material selection. This report provides the theoretical basis for leading knowledgeable researchers along the path to develop multi-photon phosphor systems. The ultimate goal, a doubling of fluorescent lamp efficacy, is not going to be easily obtained. This report begins the process and should be followed with detailed experimental and theoretical research to continue the development process.

R. Graham; W. Chow

2003-05-01

156

Rotational spectroscopy of the first excited state of the acetylenic C H stretch of 3-fluoropropyne performed by infrared-Fourier transform microwave microwave triple-resonance spectroscopy  

NASA Astrophysics Data System (ADS)

The rotational spectra of 3-fluoropropyne in the ground and first excited acetylenic C-H stretch vibrational state have been measured. The pure rotational spectrum of the normal species and the 13C isotopomers were measured using FTMW-cwMW double-resonance spectroscopy based on the Autler-Townes (AC Stark) effect. The lineshape properties of this measurement make it possible to determine the transition strength, ? J-selection rules, and the relative energy ordering of the quantum states. The frequency accuracy of this technique is tested against a previous pure rotational study of 3-fluoropropyne. The rotational spectrum of vibrationally excited state was obtained through IR-FTMW-cwMW methods. In this technique a single-longitudinal-mode pulsed infrared laser source vibrationally excites the acetylenic C-H stretch with J-selectivity. The rotational spectrum of the excited state is then obtained by FTMW and FTMW-cwMW double-resonance methods. The excited-state measurements have a signal-to-noise ratio comparable to the pure rotational spectrum. The residuals in the excited-state fit are larger than those obtained in the ground-state fit. This greater deviation from a standard asymmetric top spectrum is most likely due to weak perturbations to the acetylenic C-H spectrum.

Douglass, Kevin O.; Rees, Frances S.; Suenram, Richard D.; Pate, Brooks H.; Leonov, Igor

2005-03-01

157

Optically induced superconductivity in striped La2-xBaxCuO4 by polarization-selective excitation in the near infrared  

NASA Astrophysics Data System (ADS)

We show that superconducting interlayer coupling, which coexists with and is depressed by stripe order in La1.885Ba0.115CuO4, can be enhanced by excitation with near-infrared laser pulses. For temperatures lower than Tc=13 K, we observe a blue shift of the equilibrium Josephson plasma resonance, detected by terahertz-frequency reflectivity measurements. Key to this measurement is the ability to probe the optical properties at frequencies as low as 150 GHz, detecting the weak interlayer coupling strengths. For T >Tc a similar plasma resonance, absent at equilibrium, is induced up to the spin-ordering temperature TSO?40 K. These effects are reminiscent but qualitatively different from the light-induced superconductivity observed by resonant phonon excitation in La1.675Eu0.2Sr0.125CuO6.5. Importantly, enhancement of the below-Tc interlayer coupling and its appearance above Tc are preferentially achieved when the near-infrared pump light is polarized perpendicular to the superconducting planes, likely due to more effective melting of stripe order and the less effective excitation of quasiparticles from the Cooper pair condensate when compared to in-plane excitation.

Nicoletti, D.; Casandruc, E.; Laplace, Y.; Khanna, V.; Hunt, C. R.; Kaiser, S.; Dhesi, S. S.; Gu, G. D.; Hill, J. P.; Cavalleri, A.

2014-09-01

158

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

159

Multi-photon dressing of an anharmonic superconducting many-level quantum circuit  

E-print Network

We report on the investigation of a superconducting anharmonic multi-level circuit that is coupled to a harmonic readout resonator. We observe multi-photon transitions via virtual energy levels of our system up to the fifth excited state. The back-action of these higher-order excitations on our readout device is analyzed quantitatively and demonstrated to be in accordance with theoretical expectation. By applying a strong microwave drive we achieve multi-photon dressing of our system which is dynamically coupled by a weak probe tone. The emerging higher-order Rabi sidebands and associated Autler-Townes splittings involving up to five levels of the investigated anharmonic circuit are observed. Experimental results are in good agreement with master equation simulations.

Jochen Braumüller; Joel Cramer; Steffen Schlör; Hannes Rotzinger; Lucas Radtke; Alexander Lukashenko; Ping Yang; Michael Marthaler; Lingzhen Guo; Alexey V. Ustinov; Martin Weides

2014-10-13

160

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

NASA Astrophysics Data System (ADS)

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. Both the mechanics of transdermal drug delivery across the skin and physiological significance of the structural changes of the dermis can be monitored. Our results show that the transition dipoles of Laurdan molecules are preferentially oriented normal to the membrane surface. Furthermore, polarization imaging shows that fibrous structures in the dermis generate emission aligned strongly along the excitation polarization. This work shows that multiphoton polarization imaging can be a powerful method in identifying structural orientations in the skin and other biological structures.

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

2003-12-01

161

Coherent multi-photon interference and compensation of polarization dispersion  

E-print Network

This thesis will explore strategies for coherent manipulation of multi-photon packets. Correlated multi-photon states can arise in nonlinear optical devices. A nonlinear quantum interferometer which includes these states ...

Fini, John Michael

2001-01-01

162

Multibeam multifocal multiphoton photon counting imaging in scattering media  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is an invaluable technique for the neurological community, allowing for deep explorations within highly scattering tissues such as the brain. However, prior to this research multiphoton microscopy was limited in its ability to rapidly construct volumetric images deep within scattering specimens. This work establishes a technique that permits such exploration through the application of multiple beams separated in both space and time, where signal photons corresponding to those beams are demultiplexed through the use of a field programmable gate array. With this system a number of improvements are provided to research in scattering media, including the coveted ability to perform photon-counting imaging with multiple beams. The ability to perform these measurements with multiple beams permits unique quantitative measurements of fluorophores within living specimens, allowing new research into dynamic three-dimensional behavior occurring within the brain. Additionally, the ability to perform multimodal measurements without filtering allows for unique avenues of research where the harmonic generation is indistinguishable from the two-photon excited fluorescence. These improvements provide neuroscience researchers with a large assortment of technological tools that will permit them to perform numerous novel experiments within the brain and other highly-scattering specimens, which should one day lead to significant advances in our understanding of complex neuronal activity.

Hoover, Erich E.

163

Infrared vibrational spectroscopy of [Ru(bpy)2(bpm)]2+ and [Ru(bpy)3]2+ in the excited triplet state.  

PubMed

This work involved a detailed investigation into the infrared vibrational spectra of ruthenium polypyridyl complexes, specifically heteroleptic [Ru(bpy)2(bpm)](2+) (bpy = 2,2'-bipyridine and bpm = 2,2'-bipyrimidine) and homoleptic [Ru(bpy)3](2+), in the excited triplet state. Transient spectra were acquired 500 ps after photoexcitation, corresponding to the vibrational ground state of the excited triplet state, using time-resolved infrared spectroscopy. We assigned the observed bands to specific ligands in [Ru(bpy)2(bpm)](2+) based on the results of deuterium substitution and identified the corresponding normal vibrational modes using quantum-chemical calculations. Through this process, the more complex vibrational bands of [Ru(bpy)3](2+) were assigned to normal vibrational modes. The results are in good agreement with the model in which excited electrons are localized on a single ligand. We also found that the vibrational bands of both complexes associated with the ligands on which electrons are little localized appear at approximately 1317 and 1608 cm(-1). These assignments should allow the study of the reaction dynamics of various photofunctional systems including ruthenium polypyridyl complexes. PMID:24528148

Mukuta, Tatsuhiko; Fukazawa, Naoto; Murata, Kei; Inagaki, Akiko; Akita, Munetaka; Tanaka, Sei'ichi; Koshihara, Shin-ya; Onda, Ken

2014-03-01

164

Diffraction can mimic saturation in multiphoton absorbers  

NASA Astrophysics Data System (ADS)

Many traditional investigations of saturation in multiphoton absorbers with the z-scan method use an approximate analytical formula that assumes a steady-state approximation. Using a numerical simulation for Maxwell's equations for laser propagation including diffraction and coupled electron population dynamics, we show that the commonly used analytical formula for determining saturation in multiphoton absorbers is often incorrect, even when the sample thickness is only one diffraction length. Using published experimental data on an organic chromophore, we show that saturation, in fact, does not occur at the laser intensity values predicted for these two and three photon absorbers. We numerically fit the published experimental z-scan data and obtain new absorption coefficients for multiphoton absorbers that accurately reflect their intrinsic values. The new values are from three to ten times larger than the published values. Because multiphoton absorbers are being used more extensively in many applications such as optical limiter, medical diagnostics and two photon microscopy, it is important to have accurate values for the two and three-photon absorption coefficients. Knowing the real value of the multiphoton absorber coefficients, even for a single diffraction length, is therefore of the utmost importance. In particular, the laser intensity at which the absorber saturates can determine which absorber is useful for a particular application.

Potasek, M.; Parilov, E.; Walker, M.

2014-03-01

165

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

166

A single-photon fluorescence and multi-photon spectroscopic study of atherosclerotic lesions  

NASA Astrophysics Data System (ADS)

In this study we compare the single-photon autofluorescence and multi-photon emission spectra obtained from the luminal surface of healthy segments of artery with segments where there are early atherosclerotic lesions. Arterial tissue was harvested from atherosclerosis-prone WHHL-MI rabbits (Watanabe heritable hyperlipidemic rabbit-myocardial infarction), an animal model which mimics spontaneous myocardial infarction in humans. Single photon fluorescence emission spectra of samples were acquired using a simple spectrofluorometer set-up with 400 nm excitation. Samples were also investigated using a home built multi-photon microscope based on a Ti:sapphire femto-second oscillator. The excitation wavelength was set at 800 nm with a ~100 femto-second pulse width. Epi-multi-photon spectroscopic signals were collected through a fibre-optics coupled spectrometer. While the single-photon fluorescence spectra of atherosclerotic lesions show minimal spectroscopic difference from those of healthy arterial tissue, the multi-photon spectra collected from atherosclerotic lesions show marked changes in the relative intensity of two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) signals when compared with those from healthy arterial tissue. The observed sharp increase of the relative SHG signal intensity in a plaque is in agreement with the known pathology of early lesions which have increased collagen content.

Smith, Michael S. D.; Ko, Alex C. T.; Ridsdale, Andrew; Schattka, Bernie; Pegoraro, Adrian; Hewko, Mark D.; Shiomi, Masashi; Stolow, Albert; Sowa, Michael G.

2009-06-01

167

Interstellar polycyclic aromatic hydrocarbons - The infrared emission bands, the excitation\\/emission mechanism, and the astrophysical implications  

Microsoft Academic Search

A comprehensive study of the PAH hypothesis is presented, including the interstellar, IR spectral features which have been attributed to emission from highly vibrationally excited PAHs. Spectroscopic and IR emission features are discussed in detail. A method for calculating the IR fluorescence spectrum from a vibrationally excited molecule is described. Analysis of interstellar spectrum suggests that the PAHs which dominate

L. J. Allamandola; G. G. M. Tielens; J. R. Barker

1989-01-01

168

Intravital multiphoton microscopy for imaging hepatobiliary function  

NASA Astrophysics Data System (ADS)

In this work, intravital multiphoton microscopy is applied to the imaging of liver metabolism with the least invasiveness. We observed intravital dynamics of the uptake, processing and excretion of the organic anion species, 6-carboxyfluorescein diacetate (6-CFDA) in the hepatobiliary system. This is achieved by the use of multiphoton microscopy and an in vivo hepatic imaging chamber which allows us to image the dynamics of hepatic metabolism. Multiphoton images revealed that the hepatic processing of 6-CFDA is completed within approximately 50 minutes. The images reveal the liver metabolism of the uptake and processing of 6-CFDA from the hepatocytes, and the subsequent excretion into bile canaliculi. Our results suggest that this approach is a promising technique for investigating intravital hepatic physiology, diseases, and metabolism.

Lo, Wen; Liu, Yuan; Chen, Hsiao-Ching; Yang, Shu-Mei; Sun, Tzu-Lin; Chiou, Ling-Ling; Huang, Guan-Tarn; Dong, Chen-Yuan; Lee, Hsuan-Shu

2007-02-01

169

Multiphoton effects in coherent radiation spectra  

NASA Astrophysics Data System (ADS)

At measurements of the spectra of intense gamma radiation produced by ultrarelativistic electrons in periodic structures, pileup of arrivals to the detector of several photons from one electron can cause significant deviations of the measured spectrum from the classically evaluated one. The description of experiments then requires summation of all multiphoton contributions. We describe the corresponding resummation procedure for the photon spectral intensity, as well as for the photon multiplicity spectrum, and apply it to the study of radiation spectra with a mix of coherent and incoherent contributions. The impact of multiphoton effects on the radiation spectrum shape is investigated. The limit of high photon multiplicity for the coherent part of the radiation is explored in detail. A method for reconstruction of the underlying single-photon spectrum from the multiphoton one is formulated.

Bondarenco, M. V.

2014-07-01

170

Resonance enhanced multiphoton ionization and time-of-flight mass spectra of jet-cooled 3-chlorophenol dimer  

Microsoft Academic Search

The resonance enhanced multiphoton ionization (REMPI) excitation spectrum of jet-cooled 3-chlorophenol (3-ClP) was measured in combination with time-of-flight (TOF) mass spectrometry. In the TOF mass spectrum, 3-ClP, 3-ClP dimer and 3-ClP-water cluster cations were observed. The REMPI excitation spectrum of the dimer was observed for the first time. The low-frequency intermolecular vibrations show the hydrogen bonding of the dimer of

Seiko Nakagawa; Yoshihisa Matsushita; Tadashi Suzuki; Teijiro Ichimura

2005-01-01

171

Rapid near-infrared fluorescence excitation-emission matrix spectroscopy for multifluorophore characterization using an acousto-optic tunable filter technique  

NASA Astrophysics Data System (ADS)

We report on a novel acousto-optic tunable filter (AOTF)-based near-infrared (NIR) fluorescence excitation-emission matrix (EEM) spectroscopy technique for rapid multifluorophore characterization. We implement a unique light filtering module design by using cascaded AOTFs coupled with three orthogonally oriented polarizers to effectively remove the side-ripple artifacts of AOTFs as well as by using a pair of AOTFs coupled with two orthogonally oriented polarizers to improve detection efficiency for high-quality fluorescence EEM acquisitions. NIR fluorescence EEM spectroscopy (41 excitation wavelengths ranging from 550 to 950 nm in 10-nm increments; fluorescence emission from 570 to 1000 nm at 10-nm intervals) can be acquired from fluorescence dyes [e.g., diethylthiatricarbocyanine (DTTC) iodide, oxazine 750, and IR 140] within 10 s or even less, illustrating the potential of the AOTF-based NIR EEM technique developed for rapid multifluorophore analysis and characterization in biochemical and biomedical systems.

Li, Hao; Zheng, Wei; Huang, Zhiwei

2010-03-01

172

Infrared study on room-temperature atomic layer deposition of TiO2 using tetrakis(dimethylamino)titanium and remote-plasma-excited water vapor  

NASA Astrophysics Data System (ADS)

Room-temperature atomic layer deposition (ALD) of TiO2 was developed using tetrakis(dimethylamino)titanium (TDMAT) and a remote-plasma-excited water vapor. A growth rate of 0.157 nm/cycle at room temperature was achieved, and the TDMAT adsorption and its oxidation on TiO2 were investigated by multiple-internal-reflection infrared absorption spectroscopy. Saturated adsorption of the TDMAT occurs at exposures of ˜1 × 106 Langmuir (1 Langmuir = 1 × 10-6 Torr s) at room temperature, and the remote-plasma-excited water vapor is effective in oxidizing the TDMAT-saturated TiO2 surface. The IR study suggests that the Ti-OH plays a role of adsorption site for TDMAT. The reaction mechanism of room-temperature TiO2 ALD is discussed.

Kanomata, K.; Pansila, P.; Ahmmad, B.; Kubota, S.; Hirahara, K.; Hirose, F.

2014-07-01

173

Warm Molecular Gas in M51: Mapping the Excitation Temperature and Mass of H2 with the Spitzer Infrared Spectrograph  

Microsoft Academic Search

We have mapped the warm molecular gas traced by the H2 S(0)-H2 S(5) pure rotational mid-infrared emission lines over a radial strip across the nucleus and disk of M51 (NGC 5194) using the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. The six H2 lines have markedly different emission distributions. We obtained the H2 temperature and surface density distributions by

Gregory Brunner; Kartik Sheth; Lee Armus; Mark Wolfire; Stuart Vogel; Eva Schinnerer; George Helou; Reginald Dufour; John-David Smith; Daniel A. Dale

2008-01-01

174

Upconversion luminescence in Er3+ doped Ga10Ge25S65 glass and glass-ceramic excited in the near-infrared  

NASA Astrophysics Data System (ADS)

The infrared-to-visible frequency upconversion was investigated in Er3+-doped Ga10Ge25S65 glass and in the transparent glass-ceramic obtained by heat-treatment of the glass above its glass-transition temperature. Continuous-wave and pulsed lasers operating at 980 nm and 1480 nm were used as excitation sources. The green (2H11/2 ? 4I15/2; 4S3/2 ? 4I15/2) and red (4F9/2 ? 4I15/2) photoluminescence (PL) signals due to the Er3+ ions were characterized. The PL decay times were influenced by energy transfer among Er3+ ions, by cross-relaxation processes and by energy transfer from the Er3+ ions to the host material. The PL from the Er3+ ions hosted in the crystalline phase was distinguished only when the glass-ceramic was excited by the 1480 nm pulsed laser. The excitation pathways responsible for the green and red PL bands are discussed to explain the differences between the spectra observed under continuous-wave and pulsed excitation.

Lozano B., Whualkuer; de Araújo, Cid B.; Ledemi, Yannick; Messaddeq, Younes

2013-02-01

175

Photoinduced absorption and photoconductivity of Ge/Si quantum dots in mid-infrared range under interband excitation  

NASA Astrophysics Data System (ADS)

Photoinduced absorption and lateral photoconductivity of Ge/Si quantum dots with different doping levels are studied under interband optical excitation. The obtained spectra of absorption and photoconductivity are in good agreement. Observed photoconductivity is attributed to hole escape from ground and excited states while interlevel transitions do not impact the photoconductivity signal. Temperature dependence of photoinduced photoconductivity was measured. The decrease of photoresponse with the temperature increase is attributed to the hole recapture into the quantum dots.

Balagula, R. M.; Sofronov, A. N.; Panevin, V. Yu; Firsov, D. A.; Vorobjev, L. E.; Tonkikh, A. A.; Werner, P.

2014-10-01

176

Chemical reactions between CF2HCl and NH3 induced by IR double-beam excitation  

NASA Astrophysics Data System (ADS)

Infrared multiphoton dissociation experiments with two wavelengths in different mixtures of chlorodifluoromethane and ammonia have been carried out. It is shown that the presence of ammonia in the sample induces a decrease in the chlorodifluoromethane dissociation yield. It has been observed that the distinct chemical reaction channels are differently activated as the time delay between the two laser pulses is varied. The ratio of the obtained products in the infrared multiphoton dissociation changes with the composition of the initial mixture and are not compatible with the mechanism suggested by Sugita and Arai for this reaction in single IR wavelength excitation if it is assumed to be the only contributing mechanism other than that for direct CF2HCl dissociation and subsequent C2F4 formation from the resulting CF2 radicals. It appears that, although for simultaneous two-wavelength irradiation the presence of an accumulated solid NH4Cl deposit does not significantly influence the reaction, this is no longer the case when time delays are introduced between the two beams.

Sigüenza, C. L.; Simeonov, S. A.; Díaz, L.; González-Díaz, P. F.

1993-06-01

177

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

178

High resolution multiphoton spectroscopy by a tunable free-electron-laser light.  

PubMed

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} ^{1}S^{e} and (0,1)^{0} ^{1}D^{e} 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. PMID:25415905

Zitnik, M; Miheli?, A; Bu?ar, K; Kav?i?, M; Rubensson, J-E; Svanquist, M; Söderström, J; Feifel, R; Såthe, 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

179

Multiphoton tomography, transfection, and nanosurgery with <2-nJ, 80-MHz femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Biomedical applications of low-energy (< 2nJ) near infrared (NIR) femtosecond laser pulses provided by compact, turn-key Ti:sapphire lasers are presented in this review. Applications include (i) ultrahigh resolution optical diagnostics ("optical biopsies"), (ii) gene therapy by optical targeted transfection of cells, and (iii) ultraprecise laser therapy ("nanosurgery"). The novel femtosecond laser system DermaInspec (JenLab GmbH) enables for the first time in vivo deep tissue imaging of intracellular compartments with submicron spatial and picosecond temporal resolution in patients with dermatological disorders. Using the system FemtOcut, intracellular surgery, optical gene transfer, and intraocular refractive surgery can be performed. The major process behind the diagnostical and therapeutical laser effects is non-resonant multiphoton absorption which results in two-photon autofluorescence and second harmonic generation at transient intensities of GW/cm2 as well as multiphoton ionization and plasma formation at TW/cm2 intensities, respectively.

Koenig, Karsten

2004-06-01

180

Nonlinear magic: multiphoton microscopy in the biosciences  

Microsoft Academic Search

Multiphoton microscopy (MPM) has found a niche in the world of biological imaging as the best noninvasive means of fluorescence microscopy in tissue explants and living animals. Coupled with transgenic mouse models of disease and 'smart' genetically encoded fluorescent indicators, its use is now increasing exponentially. Properly applied, it is capable of measuring calcium transients 500 ?m deep in a

Warren R Zipfel; Rebecca M Williams; Watt W Webb

2003-01-01

181

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

182

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

183

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

184

Multiphoton blockades in pulsed regimes beyond the stationary limits  

E-print Network

We demonstrate multiphoton blockades (PB) in the pulsed regime by using Kerr nonlinear dissipative resonator driven by a sequence of Gaussian pulses. It is shown that the results obtained for single-photon, two-photon and three-photon blockades in the pulsed excitation regime differ considerably from analogous results obtained for the case of continuous-wave (cw) driving. We strongly demonstrate that for the case of cw pumping of the Kerr-nonlinear resonator there are fundamental limits on populations of lower photonic number-states (with n = 0, 1, 2, 3). Thus, such detailed comparison demonstrates that PB due to excitation with a suitable photon pulses is realized beyond the fundamental limits established for cw excitations. We analyze photon-number effects and investigate phase-space properties of PB on the base of photon number populations, the second-order correlation functions and the Wigner functions in phase space. Generation of Fock states due to PB in the pulsed regime is analysed in details.

Hovsepyan, G H; Kryuchkyan, G Yu

2014-01-01

185

Multiphoton blockades in pulsed regimes beyond stationary limits  

NASA Astrophysics Data System (ADS)

We demonstrate multiphoton blockades (PB) in the pulsed regime by using a Kerr-nonlinear dissipative resonator driven by a sequence of Gaussian pulses. It is shown that the results obtained for single-photon, two-photon, and three-photon blockades in the pulsed excitation regime differ considerably from analogous results obtained for the case of continuous-wave (cw) driving. We strongly demonstrate that for the case of cw pumping of the Kerr-nonlinear resonator there are fundamental limits on populations of lower photonic number states (with n =0, 1, 2, 3). Thus, such detailed comparison demonstrates that PB due to excitation with a suitable photon pulses is realized beyond the fundamental limits established for cw excitations. We analyze photon-number effects and investigate the phase-space properties of PB on the base of photon number populations, the second-order correlation functions, and the Wigner functions in phase space. The generation of Fock states due to PB in the pulsed regime is analyzed in details.

Hovsepyan, G. H.; Shahinyan, A. R.; Kryuchkyan, G. Yu.

2014-07-01

186

Multiphoton blockades in pulsed regimes beyond the stationary limits  

E-print Network

We demonstrate multiphoton blockades (PB) in the pulsed regime by using Kerr nonlinear dissipative resonator driven by a sequence of Gaussian pulses. It is shown that the results obtained for single-photon, two-photon and three-photon blockades in the pulsed excitation regime differ considerably from analogous results obtained for the case of continuous-wave (cw) driving. We strongly demonstrate that for the case of cw pumping of the Kerr-nonlinear resonator there are fundamental limits on populations of lower photonic number-states (with n = 0, 1, 2, 3). Thus, such detailed comparison demonstrates that PB due to excitation with a suitable photon pulses is realized beyond the fundamental limits established for cw excitations. We analyze photon-number effects and investigate phase-space properties of PB on the base of photon number populations, the second-order correlation functions and the Wigner functions in phase space. Generation of Fock states due to PB in the pulsed regime is analysed in details.

G. H. Hovsepyan; A. R. Shahinyan; G. Yu. Kryuchkyan

2014-06-04

187

Label-free discrimination of normal and pulmonary cancer tissues using multiphoton fluorescence ratiometric microscopy  

NASA Astrophysics Data System (ADS)

We performed multiphoton excited autofluorescence and second harmonic generation microscopy for the distinction of normal, lung adenocarcinoma (LAC), and squamous cell carcinoma (SCC) specimens. In addition to morphological distinction, we derived quantitative metrics of cellular redox ratios for cancer discrimination. Specifically, the redox ratios of paired normal/SCC and normal/LAC specimens were found to be 0.53±0.05/0.41±0.06 and 0.56±0.02/0.35±0.06, respectively. The lower redox ratios in cancer specimens, indicating an increase in metabolic activity. These results show that the combination of morphological multiphoton imaging along with redox ratio indices can be used for the discrimination of normal and pulmonary cancer tissues.

Wang, Chun-Chin; Wu, Ruei-Jr; Lin, Sung-Jan; Chen, Yang-Fang; Dong, Chen-Yuan

2010-07-01

188

Chapter 1: Vibrational and Electronic Wavepackets Driven by Strong Field Multiphoton Ionization  

NASA Astrophysics Data System (ADS)

We present basic theoretical ideas underlying multiphoton ionization and laser control of molecules. Approaches to describe molecular electronic structure, spinorbit coupling, dynamic Stark shifts, dressed states, and multiphoton excitations are shortly reviewed. Control techniques such as phase-dependent dissociation, photon locking, and spatial hole burning are explained and illustrated exemplarily using halogenated methanes (CH2BrI, CH2I2) as model systems. Theoretical approaches are compared with experiments and the complex signals resulting from phenomena like electronic wavepackets are elucidated and understood. Hence, we show how strong-field control concepts developed for simple systems can be transferred to more complex ones and advance our ability to control molecular dynamics.

Marquetand, P.; Weinacht, T.; Rozgonyi, T.; González-Vázquez, J.; Geißer, D.; González, L.

2014-04-01

189

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

190

Preparing Multi-photon Entangled State with Beam Splitter  

NASA Astrophysics Data System (ADS)

We propose a scheme for preparing multi-photon entangled state which is useful for sub-shot-noise sensitivity with beam splitter, where the entangled degree is measured by the reciprocal of the mean quantum Fisher information per particle (RMQFIP). The multi-photon entangled state can be prepared by adjusting the transmissivity of the beam splitter and the better multi-photon entangled state can be prepared by increasing the total number of photons.

Chen, Rong-Hua; Yi, Hong-Gang

2014-12-01

191

Generation of multi-photon entanglement  

E-print Network

We propose a new scheme to generate the multi-photon entanglement via two steps, that is, first to utilize the superconductor to create the multi-quantum-dot entanglement, and then to use the input photon to transfer it into the multi-photon entanglement. Moreover, the maximum probability for the swap of photon and quantum-dot qubits is close to unit for a single input Gaussian photon. More importantly, by mapping the multi-quantum-dot state into the coherent states of oscillators, such as cavity modes, the multi-quantum-dot entanglement in our scheme can be protected from the decoherence induced by the noise. Thus, it is possible to generate more than eight spatially separated entangled photons in the realistic experimental conditions.

Dong Xie; An Min Wang

2013-12-27

192

Serotonin: multiphoton imaging and relevant spectral data  

NASA Astrophysics Data System (ADS)

Coupling three-photon microscopy with automated stage movement can now produce a live high resolution map of the neurotransmitter serotonin in a single cross section of the whole rat brain. Accurate quantification of these serotonin images demands appropriate spectral filtering. This requires one to consider that the spectral characteristics of serotonin show a remarkable variation as it non-covalently associates with different molecules, as we discuss here. Also it is known that serotonin emission changes when it forms a covalent adduct with para-formaldehyde. This provides a potential route for producing a whole brain serotonin map using multiphoton microscopy in a fixed rat brain. Here we take the initial step showing that multiphoton microscopy of this adduct can quantitatively image chemically induced changes in serotonin distribution.

Kaushalya, S. K.; Nag, Suman; Balaji, J.; Maiti, S.

2008-02-01

193

Multiphoton adiabatic passage for atom optics applications  

SciTech Connect

We study the force exerted on two-level atoms by short, counterpropagating laser pulses. When the counterpropagating pulses overlap each other partially, multiphoton adiabatic processes are possible in several configurations, which amplify the force exerted on the atoms. We investigate the practical usefulness of such multiphoton adiabatic transitions for the manipulation of the atoms' mechanical state. In particular, we compare the efficiency of a pair of constant frequency, oppositely detuned laser pulses and that of a pair of frequency-chirped pulses. We also consider the case of prolonged exposure to a sequence of laser pulses for a duration that is comparable to or much larger than the spontaneous lifetime of the atoms. We use numerical methods to calculate the reduction of the force and the heating of the atomic ensemble when spontaneous emission cannot be neglected during the interaction. In addition, we derive simple approximate formulas for the force and the heating, and compare them to the numerical results.

Demeter, Gabor; Djotyan, Gagik P. [Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences, Konkoly-Thege Miklos ut 29-33, H-1121 Budapest (Hungary)

2009-04-15

194

Multiphoton ghost imaging with classical light  

E-print Network

One of the possible types of n-th order ghost imaging is experimentally performed using multi-photon (higher-order) intensity correlations of pseudothermal light. It is shown that although increasing the order of intensity correlations leads to the growth of ghost imaging visibility, it at the same time reduces the signal-to-noise ratio. Therefore, ghost imaging with thermal light is optimal in the second order in the intensity.

I. N. Agafonov; M. V. Chekhova; A. N. Penin

2009-11-19

195

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

196

Video-rate resonant scanning multiphoton microscopy  

PubMed Central

The abnormal tumor microenvironment fuels tumor progression, metastasis, immune suppression, and treatment resistance. Over last several decades, developments in and applications of intravital microscopy have provided unprecedented insights into the dynamics of the tumor microenvironment. In particular, intravital multiphoton microscopy has revealed the abnormal structure and function of tumor-associated blood and lymphatic vessels, the role of aberrant tumor matrix in drug delivery, invasion and metastasis of tumor cells, the dynamics of immune cell trafficking to and within tumors, and gene expression in tumors. However, traditional multiphoton microscopy suffers from inherently slow imaging rates—only a few frames per second, thus unable to capture more rapid events such as blood flow, lymphatic flow, and cell movement within vessels. Here, we report the development and implementation of a video-rate multiphoton microscope (VR-MPLSM) based on resonant galvanometer mirror scanning that is capable of recording at 30 frames per second and acquiring intravital multispectral images. We show that the design of the system can be readily implemented and is adaptable to various experimental models. As examples, we demonstrate the utility of the system to directly measure flow within tumors, capture metastatic cancer cells moving within the brain vasculature and cells in lymphatic vessels, and image acute responses to changes in a vascular network. VR-MPLSM thus has the potential to further advance intravital imaging and provide new insight into the biology of the tumor microenvironment. PMID:24353926

Kirkpatrick, Nathaniel D.; Chung, Euiheon; Cook, Daniel C.; Han, Xiaoxing; Gruionu, Gabriel; Liao, Shan; Munn, Lance L.; Padera, Timothy P.; Fukumura, Dai; Jain, Rakesh K.

2013-01-01

197

Vacuum ultraviolet and near-infrared excited luminescence properties of Ca 3(PO 4) 2: RE3+, Na + ( RE=Tb, Yb, Er, Tm, and Ho)  

NASA Astrophysics Data System (ADS)

Tb 3+, Yb 3+, Tm 3+, Er 3+, and Ho 3+ doped Ca 3(PO 4) 2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb 3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb 3+ content is comparable with that of the commercial Zn 2SiO 4:Mn 2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb 3+, Tm 3+, Er 3+, and Ho 3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb 3+-Ho 3+, Yb 3+-Er 3+, and Yb 3+-Tm 3+ in Ca 3(PO 4) 2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb 3+-Tm 3+-Er 3+-Ho 3+ in Ca 3(PO 4) 2, in which the cross-relaxation process between Er 3+ and Tm 3+, producing the 1D2- 3F4 transition of Tm 3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.

Zhang, Jia; Wang, Yuhua; Guo, Linna; Zhang, Feng; Wen, Yan; Liu, Bitao; Huang, Yan

2011-08-01

198

Laser action from (B2E-X2E)HgBr induced by UV laser multiphoton dissociation of HgBr2: measurements and experimental results  

NASA Astrophysics Data System (ADS)

Light amplification resulting from XeCl multiphoton dissociation of mercury-bromide was observed in the blue- green region between 502 and 505 nm. We report the formation of electronically excited HgBr radicals and measured the gain of the medium.

Efthimiopoulos, Tom; Zevgolis, Dimitrios; Katsenos, J.; Zigos, D.

1998-07-01

199

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

200

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

201

Distinguishing between benign and malignant melanocytic nevi by in vivo multiphoton microscopy.  

PubMed

Monitoring of atypical nevi is an important step in early detection of melanoma, a clinical imperative in preventing the disease progression. Current standard diagnosis is based on biopsy and histopathologic examination, a method that is invasive and highly dependent upon physician experience. In this work, we used a clinical multiphoton microscope to image in vivo and noninvasively melanocytic nevi at three different stages: common nevi without dysplastic changes, dysplastic nevi with structural and architectural atypia, and melanoma. We analyzed multiphoton microscopy (MPM) images corresponding to 15 lesions (five in each group) both qualitatively and quantitatively. For the qualitative analysis, we identified the morphologic features characteristic of each group. MPM images corresponding to dysplastic nevi and melanoma were compared with standard histopathology to determine correlations between tissue constituents and morphology and to evaluate whether standard histopathology criteria can be identified in the MPM images. Prominent qualitative correlations included the morphology of epidermal keratinocytes, the appearance of nests of nevus cells surrounded by collagen fibers, and the structure of the epidermal-dermal junction. For the quantitative analysis, we defined a numerical multiphoton melanoma index (MMI) based on three-dimensional in vivo image analysis that scores signals derived from two-photon excited fluorescence, second harmonic generation, and melanocyte morphology features on a continuous 9-point scale. Indices corresponding to common nevi (0-1), dysplastic nevi (1-4), and melanoma (5-8) were significantly different (P < 0.05), suggesting the potential of the method to distinguish between melanocytic nevi in vivo. PMID:24686168

Balu, Mihaela; Kelly, Kristen M; Zachary, Christopher B; Harris, Ronald M; Krasieva, Tatiana B; König, Karsten; Durkin, Anthony J; Tromberg, Bruce J

2014-05-15

202

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

203

Infrared multiphoton ignition and combustion enhancement of natural gas  

Microsoft Academic Search

The unique chemistry of methane combustion, including strong C-H bond energy, leads to difficulties in use of natural gas as an engine fuel. Problems include low combustion efficiency, knocking, unreliable ignition (misfiring), and NOx emission. It is well established that improvement of the above-mentioned combustion phenomena requires the presence of high concentration of chain-initiating and chain-branching reactive radicals. This project

Moshe Lavid; Arthur T. Poulos; Suresh K. Gulati

1993-01-01

204

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

205

Subcycle transient structures in time-dependent multiphoton-ionization rates  

NASA Astrophysics Data System (ADS)

We perform an ab initio and accurate exploration of the subcycle transient multiphoton-ionization dynamics of atomic and molecular systems subject to intense near-infrared laser fields on the subfemtosecond time scale. Multiple-ionization bursts within a single optical cycle are found in the time-dependent ionization rates not only for diatomic molecules H2+ and HHe2+, but also for the hydrogen atom. The analysis of the electron density reveals that several distinct density portions can be shaped and detached from the target within a half cycle of the laser field.

Telnov, Dmitry A.; Nasiri Avanaki, K.; Chu, Shih-I.

2014-10-01

206

Multi-photon in situ synthesis and patterning of polymer-embedded nanocrystals  

Microsoft Academic Search

The in situ synthesis and patterning of CdS nanocrystals in a polymer\\u000a matrix is performed via multiphoton absorption. Quantum-sized CdS\\u000a nanocrystals are obtained by irradiating a cadmium thiolate precursor\\u000a dispersed in a transparent polymer matrix with a focused near infrared\\u000a femtosecond laser beam. High resolution transmission electron microscopy\\u000a evidences the formation of nanocrystals with wurtzite crystalline phase.\\u000a Fluorescent, nanocomposite patterns

Andrea Camposeo; Marco Polo; Antonio A. R. Neves; Despina Fragouli; Luana Persano; Sandra Molle; Anna M. Laera; Emanuela Piscopiello; Vincenzo Resta; Athanassia Athanassiou; Roberto Cingolani; Leander Tapfer; Dario Pisignano

2012-01-01

207

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

208

Coherent multiphoton photoelectron emission from single au nanorods: the critical role of plasmonic electric near-field enhancement.  

PubMed

Electron emission from individual Au nanorods deposited on indium-tin-oxide (ITO) following excitation with femtosecond laser pulses near the rod longitudinal plasmon resonance is studied via scanning photoionization microscopy. The measured electron signal is observed to strongly depend on the excitation laser polarization and wavelength. Correlated secondary electron microscopy (SEM) and dark-field microscopy (DFM) studies of the same nanorods unambiguously confirm that maximum electron emission results from (i) laser polarization aligned with the rod long axis and (ii) laser wavelength resonant with the localized surface plasmon resonance. The experimental results are in good agreement with quantitative predictions for a coherent multiphoton photoelectric effect, which is identified as the predominant electron emission mechanism for metal nanoparticles under employed excitation conditions. According to this mechanism, the multiphoton photoemission rate is increased by over 10 orders of magnitude in the vicinity of a localized surface plasmon resonance, due to enhancement of the incident electromagnetic field in the particle near-field. These findings identify multiphoton photoemission as an extremely sensitive metric of local electric fields (i.e., "hot spots") in plasmonic nanoparticles/structures that can potentially be exploited for direct quantitation of local electric field enhancement factors. PMID:23194174

Grubisic, Andrej; Schweikhard, Volker; Baker, Thomas A; Nesbitt, David J

2013-01-22

209

Multi-Photon Entanglement Experimental Observation, Characterization, and  

E-print Network

Multi-Photon Entanglement Experimental Observation, Characterization, and Application of up to Six-Photon Entangled States Witlef Wieczorek M¨unchen 2009 #12;#12;Multi-Photon Entanglement Experimental Observation, Characterization, and Application of up to Six-Photon Entangled States Witlef Wieczorek Dissertation an der Fakult

Weinfurter, Harald

210

State-selective detection of the PbF molecule by doubly resonant multiphoton ionization  

NASA Astrophysics Data System (ADS)

Doubly resonant multiphoton ionization of PbF has been achieved via the X1?A and A?D transitions. Excitation of the A to the D state by narrow-bandwidth laser radiation is found to have a cross section of ?D=100±30Mb . The ionization potential is found to be 7.55(1) eV, in agreement with our previous result. The lifetime of the D state is found to be 250±150ps and the ionization cross section is found to be ?+=90±60Mb . These characteristics allow for efficient state-selective ionization of the PbF molecule.

Sivakumar, P.; McRaven, C. P.; Combs, Dustin; Shafer-Ray, N. E.; Ezhov, Victor

2008-06-01

211

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

212

High-resolution infrared studies in slit supersonic discharges: CH2 stretch excitation of jet-cooled CH2Cl radical  

NASA Astrophysics Data System (ADS)

First high-resolution infrared spectra are presented for jet-cooled CH2 35Cl and CH2 37Cl radicals in the symmetric (?1) CH2 stretching mode. A detailed spectral assignment yields refined lower and upper state rotational constants, as well as fine structure spin-rotation parameters from least-squares fits to the sub-Doppler line shapes for individual transitions. The rotational constants are consistent with a nearly planar structure, but do not exclude substantial large amplitude bending motion over a small barrier to planarity accessible with zero-point excitation. High level coupled cluster (singles/doubles/triples) calculations, extrapolated to the complete basis set limit, predict a slightly nonplanar equilibrium structure (?~11°), with a vibrationally adiabatic treatment of the bend coordinate yielding a v=1<--0 anharmonic frequency (393 cm-1) in excellent agreement with matrix studies (?bend~400 cm-1). The antisymmetric CH2 stretch vibration is not observed despite high sensitivity detection (signal to noise ratio >20:1) in the symmetric stretch band. This is consistent with density functional theory intensity calculations indicating a >35-fold smaller antisymmetric stretch transition moment for CH2Cl, and yet contrasts dramatically with high-resolution infrared studies of CH2F radical, for which both symmetric and antisymmetric CH2 stretches are observed in a nearly 2:1 intensity ratio. A simple physical model is presented based on a competition between bond-dipole and ``charge-sloshing'' contributions to the transition moment, which nicely explains the trends in CH2X symmetric versus asymmetric stretch intensities as a function of electron withdrawing group (X=D,Br,Cl,F).

Whitney, Erin S.; Haeber, Thomas; Schuder, Michael D.; Blair, Andrew C.; Nesbitt, David J.

2006-08-01

213

Multiphoton microscopy and fluorescence lifetime imaging provide a novel method in studying drug distribution and metabolism in the rat liver in vivo  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy has been shown to be a useful tool in studying drug distribution in biological tissues. In addition, fluorescence lifetime imaging provides information about the structure and dynamics of fluorophores based on their fluorescence lifetimes. Fluorescein, a commonly used fluorescent probe, is metabolized within liver cells to fluorescein mono-glucuronide, which is also fluorescent. Fluorescein and its glucuronide have similar excitation and emission spectra, but different fluorescence lifetimes. In this study, we employed multiphoton fluorescence lifetime imaging to study the distribution and metabolism of fluorescein and its metabolite in vivo in rat liver. Fluorescence lifetime values in vitro were used to interpret in vivo data. Our results show that the mean fluorescence lifetimes of fluorescein and its metabolite decrease over time after injection of fluorescein in three different regions of the liver. In conclusion, we have demonstrated a novel method to study a fluorescent compound and metabolite in vivo using multiphoton fluorescence lifetime imaging.

Thorling, Camilla A.; Dancik, Yuri; Hupple, Clinton W.; Medley, Gregory; Liu, Xin; Zvyagin, Andrei V.; Robertson, Tom A.; Burczynski, Frank J.; Roberts, Michael S.

2011-08-01

214

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

215

Intravital multiphoton imaging of cutaneous immune responses.  

PubMed

Varieties of immune cells orchestrate cutaneous immune responses. To capture such dynamic phenomena, intravital imaging is an important technique and it may provide substantial information that is not available using the conventional histological analysis. Multiphoton microscopy enables the direct, three-dimensional, and minimally invasive imaging of biological samples with high spatio-temporal resolution, and it has now become the leading method for in vivo imaging studies. Using fluorescent dyes and transgenic reporter animals, not only skin structures but also cell- and humor-mediated cutaneous immune responses have been visualized. PMID:24965543

Kabashima, Kenji; Egawa, Gyohei

2014-11-01

216

Multiphoton ionization/dissociation of osmium tetroxide  

SciTech Connect

The mechanisms leading to laser multiphoton ionization and dissociation (MPI/MPD) of osmium tetroxide (OsO[sub 4]) have been investigated from measurements of the kinetic energies of product ions (Os[sup +], Os[sup 2+], OsO[sup +], O[sub 2][sup +], O[sup +]) and photoelectrons as a function of the laser wavelength. Neutral channels, intermediate to the dominant Os[sup +] ionization channel, such as OsO[sub 4][r arrow]OsO[sub 4[minus][ital n

Ding, D. (Jilin University, Changchun 130023 (China)); Puretzky, A.A. (Institute of Spectroscopy, Russian Academy of Sciences, 142092 Troitsk, Moscow Region (Russian Federation)); Compton, R.N. (Chemical Physics Section, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6125 (United States) Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996 (United States))

1993-01-15

217

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

218

Femtosecond coincidence imaging of multichannel multiphoton dynamics.  

PubMed

The novel technique of femtosecond time-resolved photoelectron-photoion coincidence imaging is applied to unravel dissociative ionization processes in a polyatomic molecule. Femtosecond coincidence imaging of CF3I photodynamics illustrates how competing multiphoton dissociation pathways can be distinguished, which would be impossible using photoelectron or ion imaging alone. Ion-electron energy correlations and photoelectron angular distributions reveal competing processes for the channel producing (e(-)+CF+3+I). The molecular-frame photoelectron angular distributions of the two major pathways are strikingly different. PMID:15089669

Rijs, Anouk M; Janssen, Maurice H M; Chrysostom, Engelene T H; Hayden, Carl C

2004-03-26

219

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

220

In vivo non-invasive multiphoton tomography of human skin  

NASA Astrophysics Data System (ADS)

High resolution non-invasive 3D imaging devices are required to detect pathogenic microorganisms such as Anthrax spores, bacteria, viruses, fungi and chemical agents entering biological tissues such as the epidermis. Due to the low light penetration depth and the biodamage potential, ultraviolet light sources can not be employed to realize intratissue imaging of bio- and chemohazards. We report on the novel near infrared laser technology multiphoton tomography and the high resolution 4D imaging tool DermaInspect for non-invasive detection of intratissue agents and their influence on cellular metabolism based on multiphoton autofluorescence imaging (MAI) and second harmonic generation (SHG). Femtosecond laser pulses in the spectral range of 750 nm to 850 nm have been used to image in vivo human skin with subcellular spatial and picosecond temporal resolution. The non-linear induced autofluorescence of both, skin tissues and microorganisms, originates mainly from naturally endogenous fluorophores/protein structures like NAD(P)H, flavins, keratin, collagen, elastin, porphyrins and melanin. Bacteria emit in the blue/green spectral range due to NAD(P)H and flavoproteins and, in certain cases, in the red spectral range due to the biosynthesis of Zn-porphyrins, coproporphyrin and protoporphyrin. Collagen and exogenous non-centrosymmetric molecules can be detected by SHG signals. The system DermaInspect consists of a wavelength-tunable compact 80/90 MHz Ti:sapphire laser, a scan module with galvo scan mirrors, piezo-driven objective, fast photon detector and time-resolved single photon counting unit. It can be used to perform optical sectioning and 3D autofluorescence lifetime imaging (?-mapping) with 1 ?m spatial resolution and 270 ps temporal resolution. The parameter fluorescence lifetime depends on the type of fluorophore and its microenvironment and can be used to distinguish bio- and chemohazards from cellular background and to gain information for pathogen identification. The novel in vivo non-invasive imaging system offers the possibility to detect and to localize CB agents in tissues and to gain information on their impact on respiratory chain activity, cell division and metabolism. The system DermaInspect can also be used to detect food and water contamination.

König, Karsten; Riemann, Iris; Ehlers, Alexander; Le Harzic, Ronan

2005-10-01

221

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

222

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

223

Multiphoton microscopy and microspectroscopy for diagnostics of inflammatory and neoplastic lung  

NASA Astrophysics Data System (ADS)

Limitations of current medical procedures for detecting early lung cancers inspire the need for new diagnostic imaging modalities for the direct microscopic visualization of lung nodules. Multiphoton microscopy (MPM) provides for subcellular resolution imaging of intrinsic fluorescence from unprocessed tissue with minimal optical attenuation and photodamage. We demonstrate that MPM detects morphological and spectral features of lung tissue and differentiates between normal, inflammatory and neoplastic lung. Ex vivo MPM imaging of intrinsic two-photon excited fluorescence was performed on mouse and canine neoplastic, inflammatory and tumor-free lung sites. Results showed that MPM detected microanatomical differences between tumor-free and neoplastic lung tissue similar to standard histopathology but without the need for tissue processing. Furthermore, inflammatory sites displayed a distinct red-shifted fluorescence compared to neoplasms in both mouse and canine lung, and adenocarcinomas displayed a less pronounced fluorescence emission in the 500 to 550 nm region compared to adenomas in mouse models of lung cancer. These spectral distinctions were also confirmed by two-photon excited fluorescence microspectroscopy. We demonstrate the feasibility of applying MPM imaging of intrinsic fluorescence for the differentiation of lung neoplasms, inflammatory and tumor-free lung, which motivates the application of multiphoton endoscopy for the in situ imaging of lung nodules.

Pavlova, Ina; Hume, Kelly R.; Yazinski, Stephanie A.; Flanders, James; Southard, Teresa L.; Weiss, Robert S.; Webb, Watt W.

2012-03-01

224

Multiphoton microscopy and microspectroscopy for diagnostics of inflammatory and neoplastic lung  

PubMed Central

Abstract. Limitations of current medical procedures for detecting early lung cancers inspire the need for new diagnostic imaging modalities for the direct microscopic visualization of lung nodules. Multiphoton microscopy (MPM) provides for subcellular resolution imaging of intrinsic fluorescence from unprocessed tissue with minimal optical attenuation and photodamage. We demonstrate that MPM detects morphological and spectral features of lung tissue and differentiates between normal, inflammatory and neoplastic lung. Ex vivo MPM imaging of intrinsic two-photon excited fluorescence was performed on mouse and canine neoplastic, inflammatory and tumor-free lung sites. Results showed that MPM detected microanatomical differences between tumor-free and neoplastic lung tissue similar to standard histopathology but without the need for tissue processing. Furthermore, inflammatory sites displayed a distinct red-shifted fluorescence compared to neoplasms in both mouse and canine lung, and adenocarcinomas displayed a less pronounced fluorescence emission in the 500 to 550 nm region compared to adenomas in mouse models of lung cancer. These spectral distinctions were also confirmed by two-photon excited fluorescence microspectroscopy. We demonstrate the feasibility of applying MPM imaging of intrinsic fluorescence for the differentiation of lung neoplasms, inflammatory and tumor-free lung, which motivates the application of multiphoton endoscopy for the in situ imaging of lung nodules. PMID:22502572

Pavlova, Ina; Hume, Kelly R.; Yazinski, Stephanie A.; Flanders, James; Southard, Teresa L.; Weiss, Robert S.; Webb, Watt W.

2012-01-01

225

Imaging the morphological change of tissue structure during the early phase of esophageal tumor progression using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Esophageal cancer is a common malignancy with a very poor prognosis. Successful strategies for primary prevention and early detection are critically needed to control this disease. Multiphoton microscopy (MPM) is becoming a novel optical tool of choice for imaging tissue architecture and cellular morphology by two-photon excited fluorescence. In this study, we used MPM to image microstructure of human normal esophagus, carcinoma in situ (CIS), and early invasive carcinoma in order to establish the morphological features to differentiate these tissues. The diagnostic features such as the appearance of cancerous cells, the significant loss of stroma, the absence of the basement membrane were extracted to distinguish between normal and cancerous esophagus tissue. These results correlated well with the paired histological findings. With the advancement of clinically miniaturized MPM and the multi-photon probe, combining MPM with standard endoscopy will therefore allow us to make a real-time in vivo diagnosis of early esophageal cancer at the cellular level.

Xu, Jian; Kang, Deyong; Xu, Meifang; Zhu, Xiaoqin; Zhuo, Shuangmu; Chen, Jianxin

2012-12-01

226

Dynamic Multiphoton Imaging: A Live View from Cells to Systems  

NSDL National Science Digital Library

The application of multiphoton microscopy to the biological sciences has led to a new generation of imaging-based studies extending from the tracking of individual molecules within living cells to the observation of whole organisms

PhD Grace E. Stutzmann (University of California-Irvine); PhD Ian Parker (University of California-Irvine Department of Neurobiology and Behavior)

2005-02-01

227

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

228

Engineering multiphoton states for linear optics computation  

E-print Network

Transformations achievable by linear optical components allow to generate the whole unitary group only when restricted to the one-photon subspace of a multimode Fock space. In this paper, we address the more general problem of encoding quantum information by multiphoton states, and elaborating it via ancillary extensions, linear optical passive devices and photodetection. Our scheme stems in a natural way from the mathematical structures underlying the physics of linear optical passive devices. In particular, we analyze an economical procedure for mapping a fiducial 2-photon 2-mode state into an arbitrary 2-photon 2-mode state using ancillary resources and linear optical passive N-ports assisted by post-selection. We found that adding a single ancilla mode is enough to generate any desired target state. The effect of imperfect photodetection in post-selection is considered and a simple trade-off between success probability and fidelity is derived.

Paolo Aniello; Cosmo Lupo; Mario Napolitano; Matteo G. A. Paris

2006-05-31

229

Multiphoton microscopy of cleared mouse organs  

NASA Astrophysics Data System (ADS)

Typical imaging depths with multiphoton microscopy (MPM) are limited to less than 300 ?m in many tissues due to light scattering. Optical clearing significantly reduces light scattering by replacing water in the organ tissue with a fluid having a similar index of refraction to that of proteins. We demonstrate MPM of intact, fixed, cleared mouse organs with penetration depths and fields of view in excess of 2 mm. MPM enables the creation of large 3-D data sets with flexibility in pixel format and ready access to intrinsic fluorescence and second-harmonic generation. We present high-resolution images and 3-D image stacks of the brain, small intestine, large intestine, kidney, lung, and testicle with image sizes as large as 4096×4096 pixels.

Parra, Sonia G.; Chia, Thomas H.; Zinter, Joseph P.; Levene, Michael J.

2010-05-01

230

Maximizing fluorescence collection efficiency in multiphoton microscopy  

PubMed Central

Understanding fluorescence propagation through a multiphoton microscope is of critical importance in designing high performance systems capable of deep tissue imaging. Optical models of a scattering tissue sample and the Olympus 20X 0.95NA microscope objective were used to simulate fluorescence propagation as a function of imaging depth for physiologically relevant scattering parameters. The spatio-angular distribution of fluorescence at the objective back aperture derived from these simulations was used to design a simple, maximally efficient post-objective fluorescence collection system. Monte Carlo simulations corroborated by data from experimental tissue phantoms demonstrate collection efficiency improvements of 50% – 90% over conventional, non-optimized fluorescence collection geometries at large imaging depths. Imaging performance was verified by imaging layer V neurons in mouse cortex to a depth of 850 ?m. PMID:21934897

Zinter, Joseph P.; Levene, Michael J.

2011-01-01

231

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

232

Terahertz-pulse emission through excitation of surface  

E-print Network

Terahertz-pulse emission through excitation of surface plasmons in metallic nanostructures Gregor H ­ gratings ­ prisms ­ rough films · Rectification in a metallic grating ­ surface plasmons (SPs), electron;Introduction · Rectification on metal surfaces · Multiphoton photoelectric effect (MPPE) on metal surfaces

Strathclyde, University of

233

Stepwise multiphoton activation fluorescence reveals a new method of melanin detection  

NASA Astrophysics Data System (ADS)

The stepwise multiphoton activated fluorescence (SMPAF) of melanin, activated by a continuous-wave mode near infrared (NIR) laser, reveals a broad spectrum extending from the visible spectra to the NIR and has potential application for a low-cost, reliable method of detecting melanin. SMPAF images of melanin in mouse hair and skin are compared with conventional multiphoton fluorescence microscopy and confocal reflectance microscopy (CRM). By combining CRM with SMPAF, we can locate melanin reliably. However, we have the added benefit of eliminating background interference from other components inside mouse hair and skin. The melanin SMPAF signal from the mouse hair is a mixture of a two-photon process and a third-order process. The melanin SMPAF emission spectrum is activated by a 1505.9-nm laser light, and the resulting spectrum has a peak at 960 nm. The discovery of the emission peak may lead to a more energy-efficient method of background-free melanin detection with less photo-bleaching.

Lai, Zhenhua; Kerimo, Josef; Mega, Yair; DiMarzio, Charles A.

2013-06-01

234

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

235

In vivo multiphoton imaging of the cornea: polarization-resolved second harmonic generation from stromal collagen  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy provides specific and contrasted images of unstained collagenous tissues such as tendons or corneas. Polarization-resolved second harmonic generation (SHG) measurements have been implemented in a laserscanning multiphoton microscope. Distortion of the polarimetric response due to birefringence and diattenuation during propagation of the laser excitation has been shown in rat-tail tendons. A model has been developed to account for these effects and correct polarization-resolved SHG images in thick tissues. This new modality is then used in unstained human corneas to access two quantitative parameters: the fibrils orientation within the collagen lamellae and the ratio of the main second-order nonlinear tensorial components. Orientation maps obtained from polarization resolution of the trans-detected SHG images are in good agreement with the striated features observed in the raw images. Most importantly, polarization analysis of the epi-detected SHG images also enables to map the fibrils orientation within the collagen lamellae while epi-detected SHG images of corneal stroma are spatially homogenous and do not enable direct visualization of the fibrils orientation. Depth profiles of the polarimetric SHG response are also measured and compared to models accounting for orientation changes of the collagen lamellae within the focal volume. Finally, in vivo polarization-resolved SHG is performed in rat corneas and structural organization of corneal stroma is determined using epi-detected signals.

Latour, G.; Gusachenko, I.; Kowalczuk, L.; Lamarre, I.; Schanne-Klein, M.-C.

2012-03-01

236

Correlations in highly excited two-electron atoms - Planetary behavior  

Microsoft Academic Search

The onset of strong mixing of atomic configurations in core\\/excited autoionization states of Ba has been observed using multiphoton Isolated Core Excitation (ICE). The behavior of the different atomic configurations is categorized into two groups: states where n is much greater than m; and states where n is approximately equal to m. The spectral characteristics of 6s15 to 10sn-prime s

W. E. Cooke; R. M. Jopson; L. A. Bloomfield; R. R. Freeman; J. Bokor

1984-01-01

237

Multiphoton ionization with precise intensity control  

NASA Astrophysics Data System (ADS)

In the presence of strong laser fields (> 1012 W/cm2), atoms and molecules can simultaneously absorb many photons to exceed the ionization limit,1 leading to the ejection of photoelectrons. The analysis of photoelectron kinetic energy spectra provides valuable insight into atomic and molecular structures. The kinetic energy can be determined by measuring the time-of-flight of the electrons over a known distance. At high intensities, Rydberg states Stark-shift upward and cause a strong enhancement in the ionization rate when coming into resonance with a multiple of the photon energy.2 Traditional photoelectron and ion spectroscopy suffers from spatially averaging over all intensities within the laser focus. A novel method of time-of-flight spectroscopy has been developed that allows observation of multiphoton ionization with extremely high precision and intensity control.3 By scanning the laser-produced ionization region across a 500 u m pinhole, specific peak intensities can be spatially selected. The complexity of a Gaussian focal volume can be reduced to a "slice" that has only a one-dimensional radial intensity dependence. In addition, Intensity-Selective Scanning (ISS) yields better signal-to-noise ratios and it provides signal gains for low intensity phenomena due to the volume increase of the diverging laser beam.

Hansch, Peter; Walker, Mark A.; van Woerkom, Linn D.

1996-12-01

238

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.; Combrie, Sylvain; Colman, Pierre; Zheng, Jiangjun; De Rossi, Alfredo; Wong, Chee Wei

2013-01-01

239

Control of resonance enhanced multi-photon ionization photoelectron spectroscopy by phase-shaped femtosecond laser pulse  

SciTech Connect

In this paper, we theoretically demonstrate that the (2+1+1) resonance enhanced multi-photon ionization photoelectron spectroscopy in sodium atom can be effectively controlled by shaping femtosecond laser pulse with a {pi} phase step modulation in weak laser field, involving its total photoelectron energy, maximal photoelectron intensity, and spectroscopic bandwidth. Our results show that the total photoelectron energy can be suppressed but not enhanced, the maximal photoelectron intensity can be enhanced and also suppressed, and the photoelectron spectroscopy can be tremendously narrowed. These theoretical results can provide a feasible scheme to achieve the high-resolution photoelectron spectroscopy and study the excited state structure in atomic and molecular systems.

Zhang Shian; Lu Chenhui; Jia Tianqing; Sun Zhenrong [State Key Laboratory of Precision Spectroscopy, and Department of Physics, East China Normal University, Shanghai 200062 (China); Qiu Jianrong [State Key Laboratory of Luminescent Materials and Devices, and Institute of Optical Communication Materials, South China University of Technology, Wushan Road 381, Guangzhou 510640 (China)

2012-11-07

240

Hypericin-Mediated Destruction of Collagen Fibers Revealed by Multiphoton Microscopy  

NASA Astrophysics Data System (ADS)

Collagen is the major component of the extracellular matrix in skin, tendon, cartilage, cornea, bone, etc., and as a main structural protein is the key determinant of mechanical and functional properties of tissues and organs. Proper balance between synthesis and degradation of collagen fibers is critical for maintaining normal physiologic function; therefore, the modification of collagen fibers in a controlled manner is of high importance for biomedicine. In this work, using second harmonic generation (SHG) and two-photon excited auto-fluorescence (TPEF) microscopy, we revealed that hypericin, a natural pigment extracted from plant, induced structural modification of collagen based tissues. Dynamics of the process was monitored by time-lapse multiphoton imaging. It was demonstrated that hypericin-mediated process was considerably irreversible and has a potential to be used for destroying of abnormal tissues and treatment of some diseases.

Hovhannisyan, Ararat Zh.; Hovhannisyan, Vladimir A.; Dong, Chen-Yuan

241

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

242

Multiphoton transitions in a macroscopic quantum two-state system.  

PubMed

We have observed multiphoton transitions between two macroscopic quantum-mechanical superposition states formed by two opposite circulating currents in a superconducting loop with three Josephson junctions. Resonant peaks and dips of up to three-photon transitions were observed in spectroscopic measurements when the system was irradiated with a strong rf-photon field. The widths of the multiphoton absorption dips are shown to scale with the Bessel functions in agreement with theoretical predictions derived from the Bloch equation or from a spin-boson model. PMID:15323856

Saito, S; Thorwart, M; Tanaka, H; Ueda, M; Nakano, H; Semba, K; Takayanagi, H

2004-07-16

243

Optical clearing and multiphoton imaging of paraffin-embedded specimens  

NASA Astrophysics Data System (ADS)

New labeling, imaging, or analysis tools could provide new retrospective insights when applied to archived, paraffin-embedded samples. Deep-tissue multiphoton microscopy of paraffin-embedded specimens is achieved using optical clearing with mineral oil. We tested a variety of murine tissue specimens including skin, lung, spleen, kidney, and heart, acquiring multiphoton autofluorescence and second-harmonic generation, and pump-probe images This technique introduces the capability for non-destructive 3-dimensional microscopic imaging of existing archived pathology specimens, enabling retrospective studies.

Wilson, Jesse W.; Degan, Simone; Fischer, Martin C.; Warren, Warren S.

2013-02-01

244

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

245

Multiphotons and photon jets from new heavy vector bosons  

NASA Astrophysics Data System (ADS)

We discuss an extension of the Standard Model with a new vector boson decaying predominantly into a multiphoton final state through intermediate light degrees of freedom. The model has a distinctive phase in which the photons are collimated. As such, they would fail the isolation requirements of standard multiphoton searches, but group naturally into a novel object, the “photon-jet”. Once defined, the photon-jet object facilitates more inclusive searches for similar phenomena. We present a concrete model, discuss photon jets more generally, and outline some strategies that may prove useful when searching for such objects.

Toro, Natalia; Yavin, Itay

2012-09-01

246

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

SciTech Connect

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; Janssen, Maurice H. M., E-mail: m.h.m.janssen@vu.nl [LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands)] [LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Powis, Ivan [School of Chemistry, University of Nottingham, Nottingham NG7 2RD (United Kingdom)] [School of Chemistry, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2013-12-21

247

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

248

Multiphoton Coherent Manipulation in Large Spin Qubits  

NASA Astrophysics Data System (ADS)

Manipulation of quantum information allows certain algorithms to be performed at unparalleled speeds. Photons are an ideal choice to manipulate qubits as they interact with quantum systems in predictable ways. They are a versatile tool for manipulating, reading/coupling qubits and for encoding/transferring quantum information over long distances. Spin-based qubits have well known behavior under photon driving and can be potentially operated up to room temperature. When diluted enough to avoid uncontrolled spin-spin interactions, a variety of spin qubits show long coherence times, e.g. the nitrogen vacancies in pure diamonds (1,2), nitrogen atoms trapped in a C60 cage (3), Ho3+ and Cr5+ ions (4,5) and molecular magnets (6,7). We have used large spin Mn2+ ions (S=5/2) to realize a six level system that can be operated by means of single as well as multi-photon coherent Rabi oscillations (8). This spin system has a very small anisotropy whose effect can be tuned in-situ to turn the system into a multi-level harmonic system. This offer new ways of manipulating, reading and resetting a spin qubit. Decoherence effects are strongly reduced by the quasi-isotropic electron interaction with the crystal field and with the 55Mn nuclear spins. [0pt] 1. R. Hanson et al., Science 320, 352 (2008). [0pt] 2. M.V. Gurudev Dutt et al., Science 316, 1312 (2007). [0pt] 3. G.W. Morley et al., Phys. Rev. Lett. 98, 220501 (2007). [0pt] 4. S. Bertaina et al., Nat. Nanotech. 2, 39 (2007). [0pt] 5. S. Nellutla et al., Phys. Rev. Lett. 99, 137601 (2007). [0pt] 6. A. Ardavan et al., Phys. Rev. Lett. 98, 057201 (2007). [0pt] 7. S. Bertaina et al., Nature 453, 203,(2008). [0pt] 8. S. Bertaina et al., submitted.

Chiorescu, Irinel

2009-03-01

249

Intense Visible and Near-Infrared Upconversion Photoluminescence in Colloidal LiYF4:Er3+ Nanocrystals under Excitation at 1490 nm  

PubMed Central

We report intense upconversion photoluminescence (PL) in colloidal LiYF4:Er3+ nanocrystals under excitation with telecom-wavelength at 1490 nm. The intensities of two- and three-photon anti-Stokes upconversion PL bands are higher than or comparable to that of the Stokes emission under excitation with low power density in the range of 5–120 W/cm2. The quantum yield of the upconversion PL was measured to be as high as ~1.2±0.1%, which is almost 4 times higher than the highest upconversion PL quantum yield reported up to date for lanthanide-doped nanocrystals in 100 nm sized hexagonal NaYF4:Yb3+20%, Er3+2% using excitation at ~980 nm. Power dependence study revealed that the intensities of all PL bands have linear dependence on the excitation power density, which was explained by saturation effects in the intermediate energy states. PMID:21557587

Chen, Guanying; Ohulchanskyy, Tymish Y.; Kachynski, Aliaksandr; Agren, Hans; Prasad, Paras N.

2012-01-01

250

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

251

Multiphoton Imaging of Renal Regulatory Mechanisms - Supplemental Videos  

NSDL National Science Digital Library

Video 1 - SNGFR - Video 2 - PT calcium oscillations - Video 3 - TGF DIC - Video 4 - renin release - Video 5 - oscillations time From Peti-Peterdi J, Toma I, Sipos A, Vargas SL. Multiphoton Imaging of Renal Regulatory Mechanisms. Physiology 24: 88-96, 2009

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

252

Multiphoton microspectroscopy in living plant cells  

NASA Astrophysics Data System (ADS)

Microspectroscopic measurements in plant cells are complicated by the presence of dense cellular structures such as the cell wall that causes severe light scattering. In addition, the low penetration depth of the excitation light limits the fluorescence signal originating from deeper cell layers in thick multi-cellular plant preparations when single-photon excitation (SPE) is applied. However, two-photon excitation (TPE) can overcome these problems. We report on two-photon microscopy studies of Histone 2B-YFP, a nuclear-expressed protein involved in chromatin packaging. In contrast to SPE, TPE allows imaging throughout the whole root. Therefore by using TPE it was also possible to visualize the root quiescent centers using SCARECROW-EGFP localized in the middle of the root. The interactions between various members of the Arabidopsis thaliana embryogenesis receptor kinase family (AtSERK) have been studied by monitoring Forster resonance energy transfer (FRET) between AtSERK-ECFP and -EYFP fusion proteins using fluorescence lifetime imaging microscopy (FLIM) of the two-photon excited ECFP component.

Borst, Jan-Willem; Hink, Mark A.; van Hoek, Arie; Visser, A. J. W. G.

2003-07-01

253

Novel techniques with multiphoton microscopy: Deep-brain imaging with microprisms, neurometabolism of epilepsy, and counterfeit paper money detection  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is a laser-scanning fluorescence imaging method with extraordinary potential. We describe three innovative multiphoton microscopy techniques across various disciplines. Traditional in vivo fluorescence microscopy of the mammalian brain has a limited penetration depth (<400 microm). We present a method of imaging 1 mm deep into mouse neocortex by using a glass microprism to relay the excitation and emission light. This technique enables simultaneous imaging of multiple cortical layers, including layer V, at an angle typical of slice preparations. At high-magnification imaging using an objective with 1-mm of coverglass correction, resolution was sufficient to resolve dendritic spines on layer V GFP neurons. Functional imaging of blood flow at various neocortical depths is also presented, allowing for quantification of red blood cell flux and velocity. Multiphoton fluorescence lifetime imaging (FLIM) of NADH reveals information on neurometabolism. NADH, an intrinsic fluorescent molecule and ubiquitous metabolic coenzyme, has a lifetime dependent on enzymatic binding. A novel NADH FLIM algorithm is presented that produces images showing spatially distinct NADH fluorescence lifetimes in mammalian brain slices. This program provides advantages over traditional FLIM processing of multi-component lifetime data. We applied this technique to a GFP-GFAP pilocarpine mouse model of temporal lobe epilepsy. Results indicated significant changes in the neurometabolism of astrocytes and neuropil in the cell and dendritic layers of the hippocampus when compared to control tissue. Data obtained with NADH FLIM were subsequently interpreted based on the abnormal activity reported in epileptic tissue. Genuine U.S. Federal Reserve Notes have a consistent, two-component intrinsic fluorescence lifetime. This allows for detection of counterfeit paper money because of its significant differences in fluorescence lifetime when compared to genuine paper money. We used scanning multiphoton laser excitation to sample a ˜4 mm2 region from 54 genuine Reserve Notes. Three types of counterfeit samples were tested. Four out of the nine counterfeit samples fit to a one-component decay. Five out of nine counterfeit samples fit to a two-component model, but are identified as counterfeit due to significant deviations in the longer lifetime component compared to genuine bills.

Chia, Thomas H.

254

The two-photon excitation of SiO2-coated Y2O3:Eu3+ nanoparticles by a near-infrared femtosecond laser  

Microsoft Academic Search

In order to improve the photoluminescence property of Eu3+-doped nanoparticles, Y2O3:Eu3+ nanoparticles were synthesized using the Pechini-type sol-gel method, then coated with SiO2 shells by using the Stöber method for different coating times. The SiO2-coated nanoparticles were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, and their photoluminescence spectra were recorded

Qiang Lü; Ai Hua Li; Feng Yun Guo; Liang Sun; Lian Cheng Zhao

2008-01-01

255

The two-photon excitation of SiO2-coated Y2O3:Eu3+ nanoparticles by a near-infrared femtosecond laser  

Microsoft Academic Search

In order to improve the photoluminescence property of Eu3+-doped nanoparticles, Y2O3:Eu3+ nanoparticles were synthesized using the Pechini-type sol–gel method, then coated with SiO2 shells by using the Stöber method for different coating times. The SiO2-coated nanoparticles were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy, and their photoluminescence spectra were recorded

Qiang Lü; AiHua Li; FengYun Guo; Liang Sun; LianCheng Zhao

2008-01-01

256

Terahertz-pulse emission through excitation of surface plasmons in metallic nanostructures  

Microsoft Academic Search

The second-order processes of optical rectification and photoconduction are well known and widely used to produce ultrafast electromagnetic pulses in the terahertz frequency domain. We present a new form of rectification relying on the excitation of surface plasmons (SPs) in metallic nanostructures. Multiphoton ionization and ponderomotive acceleration of electrons in the enhanced evanescent field of the SPs, results in a

Gregor H. Welsh; Klaas Wynne

2008-01-01

257

Quenching nitrogen-vacancy center photoluminescence with an infrared pulsed laser  

NASA Astrophysics Data System (ADS)

Diamond nanocrystals containing nitrogen-vacancy (NV) color centers have been used in recent years as fluorescent probes for near-field and cellular imaging. In this work, we report that an infrared (IR) pulsed excitation beam can quench the photoluminescence of a NV color center in a diamond nanocrystal (size <50 nm) with an extinction ratio as high as ?90%. We attribute this effect to the heating of the nanocrystal consecutive to multi-photon absorption by the diamond matrix. This quenching is reversible: the photoluminescence intensity goes back to its original value when the IR laser beam is turned off, with a typical response time of 100 ps, allowing for fast control of NV color center photoluminescence. We used this effect to achieve the sub-diffraction-limited imaging of fluorescent diamond nanocrystals on a coverglass. For that, as in the ground state depletion super-resolution technique, we combined the green excitation laser beam with the control IR depleting one after shaping its intensity profile in a doughnut form, so that the emission comes only from the sub-wavelength size central part.

Lai, N. D.; Faklaris, O.; Zheng, D.; Jacques, V.; Chang, H.-C.; Roch, J.-F.; Treussart, F.

2013-03-01

258

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

259

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

260

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

261

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry using a femtosecond laser.  

PubMed

A laser can be used for the selective excitation and subsequent ionization of a molecule with an absorption band at the laser wavelength. This technique of multiphoton ionization (MPI), when combined with time-of-flight mass spectrometry (TOF-MS), permits the efficient detection of induced ions in mass analysis. This combination of MPI/TOF-MS can be coupled with gas chromatography (GC) to achieve even more enhanced selectivity. Thus, GC/MPI/TOF-MS can be employed for trace analysis of samples containing numerous chemical species. A variety of laser sources have been used for this purpose. Since molecules that are classified as environmental pollutants frequently contain chlorine and bromine atoms, the lifetime of the excited state can be decreased by energy transfer from the singlet to triplet levels by spin-orbit interaction. A high-power femtosecond laser with a pulse width shorter than the lifetime of the analyte molecule provides femtogram or even subfemtogram detection limits, which have not yet been achieved using the most sensitive high-resolution double-focus sector-type mass spectrometers. Numerous environmental pollutants such as dioxins in soils and pesticides in foods have been successfully quantified using GC/MPI/TOF-MS, and this technique has proven itself to be a useful and practical method for trace analysis. PMID:23612871

Imasaka, Totaro

2013-09-01

262

In vivo multiphoton imaging of obstructive cholestasis in mice  

NASA Astrophysics Data System (ADS)

Combining multiphoton microscopy with a newly designed hepatic imaging window, we acquired in vivo images of mice obstructive cholestasis. We observed that in mice with bile duct ligation, bile canaliculi failed to appear during the whole observation period over 100 minutes following carboxyfluorescein diacetate injection, whereas the fluorescence was retained much longer within sinusoids. Furthermore, the fluorescence intensities in sinusoids were persistently higher than in hepatocytes during the course.

Li, Feng-Chieh; Lee, Yu Yang; Chiou, Ling-Ling; Lee, Hsuan-Shu; Dong, Chen-Yuan

2010-02-01

263

Spectroscopic analysis of keratin endogenous signal for skin multiphoton microscopy  

E-print Network

-439 (2003) 4. G. Cox, E. Kable, A. Jones, I. Fraser, K. Marconi and M. D. Gorrell, "3-dimensional imaging diagnosis); 190.4180 (multiphoton processes) References and links 1. W. Denk, J. H. Strickler and W. W. Webb of collagen using second harmonic generation," J. Struct. Biol. 141, 53-62 (2003) 5. C.-K. Sun, C.-C. Chen, S.-W

Paris-Sud XI, Université de

264

Excited states and electronic spectra of annulated dinuclear free-base phthalocyanines: A theoretical study on near-infrared-absorbing dyes  

NASA Astrophysics Data System (ADS)

The electronic excited states and electronic absorption spectra of annulated dinuclear free-base phthalocyanine (C58H30N16) are studied through quantum chemical calculations using the symmetry-adapted cluster-configuration interaction (SAC-CI) method. Three tautomers are possible with respect to the position of the pyrrole protons; therefore, the SAC-CI calculations for these tautomers were performed. The structures of the Q-band states are discussed based on the character of their molecular orbitals. The lower energy shift of the Q-bands because of dimerization is explained by the decrease in the HOMO-LUMO gaps resulting from the bonding and antibonding interactions between the monomer units. The electronic dipole moments of the nonsymmetric tautomer were calculated, and the possibility of charge-separated excited states is discussed. The relative energies of these tautomers are examined using density functional theory (DFT) calculations for several peripheral substituents. The relative energies of these tautomers significantly depend on the substituents, and therefore, the abundance ratios of the three tautomers were affected by the substituents. The absorption spectra were simulated from the SAC-CI results weighted by the Boltzmann factors obtained from the DFT calculations. The SAC-CI spectra reproduce the experimental findings well. The thermal-averaged SAC-CI spectra could explain the observed substituent effect on the structure of the Q-bands in terms of the relative stabilities and the abundance ratios of the tautomers. The SAC-CI and time-dependent density functional theory calculations are also compared. The CAM-B3LYP results agreed with the trends of the SAC-CI results; however, the CAM-B3LYP calculation overestimated the excitation energies in comparison with the SAC-CI and experimental results.

Fukuda, Ryoichi; Ehara, Masahiro

2012-03-01

265

Multiphoton Microscopy of Cleared Mouse Brain Expressing YFP  

PubMed Central

Multiphoton microscopy of intrinsic fluorescence and second harmonic generation (SHG) of whole mouse organs is made possible by optically clearing the organ before imaging.1,2 However, for organs that contain fluorescent proteins such as GFP and YFP, optical clearing protocols that use methanol dehydration and clear using benzyl alcohol:benzyl benzoate (BABB) while unprotected from light3 do not preserve the fluorescent signal. The protocol presented here is a novel way in which to perform whole organ optical clearing on mouse brain while preserving the fluorescence signal of YFP expressed in neurons. Altering the optical clearing protocol such that the organ is dehydrated using an ethanol graded series has been found to reduce the damage to the fluorescent proteins and preserve their fluorescent signal for multiphoton imaging.4 Using an optimized method of optical clearing with ethanol-based dehydration and clearing by BABB while shielded from light, we show high-resolution multiphoton images of yellow fluorescent protein (YFP) expression in the neurons of a mouse brain more than 2 mm beneath the tissue surface. PMID:23023035

Murray, Teresa A.; Levene, Michael J.

2012-01-01

266

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

267

Multi-Photon and Entangled-Photon Imaging, Lithography, and Spectroscopy  

E-print Network

Multi-Photon and Entangled-Photon Imaging, Lithography, and Spectroscopy Malvin Carl Teich Columbia on NEW SCIENCE AND TECHNOLOGIES using ENTANGLED PHOTONS (NSTEP) OSAKA: 8 July 2013 Photonics Center media, offers a whole raft of useful applications in photonics, including multiphoton microscopy [1

Teich, Malvin C.

268

Volume 52, number 3 CHEMICAL PHYSICS LETTERS 15 December 1977 MULTIPHOTON IONIZATION  

E-print Network

Volume 52, number 3 CHEMICAL PHYSICS LETTERS 15 December 1977 MULTIPHOTON IONIZATION: A METHOD state distribution of this molecule. A tunable dye laser is swept through the w.ivclen$h region of the Naz B-X system and positive ions are counted as a function of laser wavelength. Multiphoton ionization

Zare, Richard N.

269

A least squares approach to estimating the probability distribution of unobserved data in multiphoton microscopy  

Microsoft Academic Search

Multi-photon microscopy has provided biologists with unprecedented opportunities for high resolution imaging deep into tissues. Unfortunately deep tissue multi-photon microscopy images are in general noisy since they are acquired at low photon counts. To aid in the analysis and segmentation of such images it is sometimes necessary to initially enhance the acquired images. One way to enhance an image is

Paul Salama

2008-01-01

270

Design and implementation of fiber-based multiphoton endoscopy with microelectromechanical systems  

E-print Network

indicates that the MEMS scanner can potentially support high-resolution multiphoton imaging. The DCPCF- limation and a focusing lens provides the optimum imaging perfor- mance and packaging flexibility of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.3127203 Keywords: multiphoton microscopy MPM

Chen, Zhongping

271

Corneal imaging and refractive index measurement using a combined multiphoton microscopy and optical coherence tomography system  

NASA Astrophysics Data System (ADS)

Refractive index (RI) is the optical property of a medium that describes its ability to bend incident light. The corneal refractive index is an especially important measurement in corneal and intraocular refractive surgery where its precise estimation is necessary to obtain accurate surgical outcomes. In this study, we calculated the corneal RI using a combined multiphoton microscopy (MPM) and optical coherence tomography (OCT) system. MPM excites and detects nonlinear signals including two photon excitation fluorescence (TPEF) and second harmonic generation (SHG). TPEF signals are observed from NADH in the cytoplasm, allowing MPM to image the cellular structures in the corneal epithelium and endothelium. SHG signals are observed from collagen, an abundant connective tissue found in the stroma. Optical coherence tomography (OCT) produces cross-sectional, structural images based on the interference fringes created by the reflected light from the sample and reference arms. Our system uses a single sub-10 fs Ti: sapphire laser source which is good for both MPM excitation and OCT resolution. The MPM and OCT images are coregistered when they are taken successively because their axial resolutions are similar and the system shares the laser source and the scanning unit. We can calculate the RI by measuring the optical thickness and the optical path length of the cornea from the MPM and OCT images respectively. We have imaged and calculated the RI of murine and piscine corneas. We were able to see the epithelial, stromal, and endothelial layers and compare their relative thicknesses and the organization of the stromal collagen lamellae. Our results showed that our system can provide both functional and structural information about the cornea and measure the RI of multi-layered tissues.

Lai, Tom; Chong, Shau Poh; Zhou, Yifeng; Moloney, Gregory; Tang, Shuo

2013-02-01

272

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

273

Cryogenic exciter  

DOEpatents

The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

Bray, James William (Niskayuna, NY); Garces, Luis Jose (Niskayuna, NY)

2012-03-13

274

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

275

Dressed-atom multiphoton analysis of anomalous electromagnetically induced absorption.  

PubMed

A method to interpret probe spectra of driven degenerate atomic systems is discussed. The dressed-atom multiphoton spectroscopy (DAMS) is based on a dressing of the atomic system with the strong coupling field, followed by a perturbative treatment of the probe field interaction. As an example, we apply the DAMS to provide a clear interpretation for anomalous electromagnetically induced absorption (EIA), which cannot be explained by spontaneous transfer of coherence. We show that anomalous EIA arises from quantum interference among competing two-photon transitions and explain the different dependences on the coupling field strength observed for various angular momentum setups. PMID:20867096

Chou, Hsiang-Shun; Evers, Jörg

2010-05-28

276

Dressed-Atom Multiphoton Analysis of Anomalous Electromagnetically Induced Absorption  

NASA Astrophysics Data System (ADS)

A method to interpret probe spectra of driven degenerate atomic systems is discussed. The dressed-atom multiphoton spectroscopy (DAMS) is based on a dressing of the atomic system with the strong coupling field, followed by a perturbative treatment of the probe field interaction. As an example, we apply the DAMS to provide a clear interpretation for anomalous electromagnetically induced absorption (EIA), which cannot be explained by spontaneous transfer of coherence. We show that anomalous EIA arises from quantum interference among competing two-photon transitions and explain the different dependences on the coupling field strength observed for various angular momentum setups.

Chou, Hsiang-Shun; Evers, Jörg

2010-05-01

277

High-Visibility Multi-Photon Interference of Classical Light  

E-print Network

It is shown that the visibility of multi-photon interference for classical sources grows rapidly with the order of interference. For three-photon and four-photon interference of two coherent sources, the visibility can be as high as 81.9% and 94.4%, respectively, - much higher than the 'classical limit' of two-photon interference (50%). High-visibility three-photon and four-photon interference has been observed in experiment, for both coherent and pseudo-thermal light.

I. N. Agafonov; M. V. Chekhova; T. Sh. Iskhakov; A. N. Penin

2007-05-07

278

Multi-photon signatures at the Fermilab Tevatron  

E-print Network

Fermiophobic Higgs bosons $h_f$ exhibiting large branching ratios to two photons can arise in models with two or more scalar doublets and/or triplets. In such models the conventional production mechanisms at hadron colliders may be rendered ineffective due to severe mixing angle suppression. In this scenario, double fermiophobic Higgs production may proceed via complementary mechanisms leading to events with up to 4 photons. We perform a simulation of the detection prospects of $h_f$ in the multi-photon (>3) channel at the Fermilab Tevatron and show that a sizeable region of the ($m_{H^\\pm},m_{h_f}$) parameter space can be probed during Run II.

A. G. Akeroyd; A. Alves; M. A. Diaz; O. J. P. Eboli

2005-12-06

279

Multiphoton ionization of ions, neutrals, and clusters. Final report  

SciTech Connect

A multiyear research program investigating molecular detection methods based on multiphoton spectroscopy has been completed under DOE sponsorship. A number of new laser-based spectroscopic methods were developed and applied to a variety of aromatic hydrocarbons, including monomer and cluster species. The objectives of sensitivities approaching single molecule detection combined with high selectivity were achieved. This report references the status of the field at the beginning of this work and summarizes the significant progress during the period from 1987 onward. Detailed scientific findings from the studies are presented in the published literature referenced throughout this report.

Wessel, J.

1995-12-28

280

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

281

Strong field Multiphoton processes in the high-frequency limit  

NASA Astrophysics Data System (ADS)

Last fall, the Linac Coherent Light Source at SLAC National Accelerator Laboratory has delivered users the world first X-ray free electron laser, allowing studying X-ray matter interaction at unprecedented photon flux. We will present the first attempts at observing multiphoton ionization in the X-ray regime, which have been realized by measuring both electron and ion spectra from the ionization of rare gases in the AMO end station. In addition to gaining insight into this new regime, our experiments also participated towards the characterization of this new light source (intensity, harmonic content).

Doumy, Gilles; Roedig, Christoph; Dichiara, Anthony; Blaga, Cosmin; Dimauro, Louis; Agostini, Pierre; Hoener, Matthias; Fang, Li; Berrah, Norrah; Young, Linda; Kanter, Elliot; Kraessig, Bertold; Southworth, Stephen; Santra, Robin; Pratt, Stephen; Coffee, Ryan; Bucksbaum, Phil; Cryan, James; Glownia, James; Ghimire, Shambhu; Reis, David; Kuebel, Matthias; Paulus, Gerhard; Bozek, John; Bostedt, Christoph

2010-03-01

282

Resonant multi-photon IR dissociation spectroscopy of a trapped and sympathetically cooled biomolecular ion species  

E-print Network

In this work we demonstrate vibrational spectroscopy of polyatomic ions that are trapped and sympathetically cooled by laser-cooled atomic ions. We use the protonated dipeptide tryptophane-alanine (HTyrAla+) as a model system, cooled by Barium ions to less than 800mK secular temperature. The spectroscopy is performed on the fundamental vibrational transition of a local vibrational mode at 2.74 {\\mu}m using a continuous-wave optical parametric oscillator (OPO). Resonant multi-photon IR dissociation spectroscopy (without the use of a UV laser) generates charged molecular fragments, which are sympathetically cooled and trapped, and subsequently released from the trap and counted. We measured the cross section for R-IRMPD under conditions of low intensity, and found it to be approximately two orders smaller than the vibrational excitation cross section. The observed rotational bandwidth of the vibrational transition is larger than the one expected from the combined effects of 300 K black-body temperature, conform...

Wellers, Ch; Vasilyev, S; Offenberg, D; Schiller, S

2011-01-01

283

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

284

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

285

Rigid and high NA multiphoton fluorescence GRIN-endoscopes  

NASA Astrophysics Data System (ADS)

Multiphoton autofluorescence imaging offers minimal-invasive examination of cells without the need of staining and complicated confocal detection systems. Therefore, it is especially interesting for non-invasive clinical diagnostics. To extend this sophisticated technique from superficial regions to deep lying cell layers, internal body parts and specimens difficult of access, the bulky optics need to be reduced in diameter. This is done by tiny GRIN-optics, based on a radial gradient in the reflective index. Of especial interest for multi-photon applications is the newly developed GRIN-lens assembly with increased numerical aperture. High resolution images of plant tissue, hair and cells show the improved image quality,compared to classical GRIN-lenses. The rigid GRIN-endoscopes are already applied in wound healing studies. Here, the GRIN-lenses with diameters smaller than 3 mm enter small skin depressions. They reproduce the focus of a conventional laser scanning tomograph tens of mm apart in the specimen under study. We present first clinical measurements of elastin and SHG of collagen of in-vivo human skin of venous ulcers (ulcer curis).

Schenkl, Selma; Ehlers, Alexander; Le Harzic, Ronan; Stark, Martin; Riemann, Iris; Messerschmidt, Bernhard; Kaatz, Martin; König, Karsten

2007-07-01

286

Multiphoton ionization and stabilization of helium in superintense xuv fields  

NASA Astrophysics Data System (ADS)

Multiphoton ionization of helium is investigated in the superintense field regime, with particular emphasis on the role of the electron-electron interaction in the ionization and stabilization dynamics. To accomplish this, we solve ab initio the time-dependent Schrödinger equation with the full electron-electron interaction included. By comparing the ionization yields obtained from the full calculations with the corresponding results of an independent-electron model, we come to the somewhat counterintuitive conclusion that the single-particle picture breaks down at superstrong field strengths. We explain this finding from the perspective of the so-called Kramers-Henneberger frame, the reference frame of a free (classical) electron moving in the field. The breakdown is tied to the fact that shake-up and shake-off processes cannot be properly accounted for in commonly used independent-electron models. In addition, we see evidence of a change from the multiphoton to the shake-off ionization regime in the energy distributions of the electrons. From the angular distribution, it is apparent that the correlation is an important factor even in this regime.

Sørngård, S. A.; Askeland, S.; Nepstad, R.; Førre, M.

2011-03-01

287

Infrared planar laser-induced fluorescence imaging and applications to imaging of carbon monoxide and carbon dioxide  

Microsoft Academic Search

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

Brian James Kirby

2001-01-01

288

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

289

Infrared Astronomy  

NSDL National Science Digital Library

This website from NASA's Infrared Astrophysics Data Center describes: the discovery of infrared waves; what infrared waves are and how they are used in astronomy; atmospheric windows; near, middle, and far infrared; the infrared universe; and infrared (IR) spectroscopy. It also provides an IR astronomy timeline; history and development of IR detector technology; information on projects, news and discoveries; an IR gallery; classroom activities; and links for getting involved in astronomy.

Hermans-Killam, Linda

290

Exciter switch  

NASA Technical Reports Server (NTRS)

A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

Mcpeak, W. L.

1975-01-01

291

Multiphoton ionization of CF{sub 3}I clusters by ultraviolet laser radiation  

SciTech Connect

The results of the investigation of the multiphoton ionization of (CF{sub 3}I){sub n} clusters by ultraviolet laser radiation are reported. The yields of the I{sub 2}{sup +} and I{sup +} ions, which are the products of the multiphoton ionization, have been measured as functions of the intensity of the ultraviolet radiation at the wavelengths of 308 and 232.5 nm. The degree of multiphoton ionization has been determined and appears to depend on the wavelength of radiation. The velocity distributions of the products have been measured in detail for various wavelengths and various polarizations of radiation. The anisotropy parameters of the velocity distributions of the produced ions and their kinetic energy have been determined. After analysis of the data, a mechanism of the multiphoton ultraviolet ionization of the clusters under investigation has been proposed. This mechanism depends on the used wavelengths.

Apatin, V. M.; Lokhman, V. N., E-mail: lokhman@isan.troitsk.ru; Ogurok, D. D.; Poydashev, D. G.; Ryabov, E. A., E-mail: ryabov@isan.troitsk.ru [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)

2011-01-15

292

Simultaneous imaging of GFP, CFP and collagen in tumors in vivousing multiphoton microscopy  

E-print Network

Background: The development of multiphoton laser scanning microscopy has greatly facilitated the imaging of living tissues. However, the use of genetically encoded fluorescent proteins to distinguish different cell types ...

Sahai, Erik

293

Multiphoton ionization of CF3I clusters by ultraviolet laser radiation  

NASA Astrophysics Data System (ADS)

The results of the investigation of the multiphoton ionization of (CF3I) n clusters by ultraviolet laser radiation are reported. The yields of the I{2/+} and I+ ions, which are the products of the multiphoton ionization, have been measured as functions of the intensity of the ultraviolet radiation at the wavelengths of 308 and 232.5 nm. The degree of multiphoton ionization has been determined and appears to depend on the wavelength of radiation. The velocity distributions of the products have been measured in detail for various wavelengths and various polarizations of radiation. The anisotropy parameters of the velocity distributions of the produced ions and their kinetic energy have been determined. After analysis of the data, a mechanism of the multiphoton ultraviolet ionization of the clusters under investigation has been proposed. This mechanism depends on the used wavelengths.

Apatin, V. M.; Lokhman, V. N.; Ogurok, D. D.; Poydashev, D. G.; Ryabov, E. A.

2011-01-01

294

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.

295

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

296

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.

1998-01-01

297

Multiphoton Microscopy and Interaction of Intense Light Pulses with Polymers  

NASA Astrophysics Data System (ADS)

The nanoscale manipulation of soft-matter, such as biological tissues, in its native environment has promising applications in medicine to correct for defects (eg. eye cataracts) or to destroy malignant regions (eg. cancerous tumours). To achieve this we need the ability to first image and then do precise ablation with sub-micron resolution with the same setup. For this purpose, we designed and built a multiphoton microscope and tested it on goldfish gills and bovine cells. We then studied light-matter interaction on a hard polymer (PMMA) because the nature of ablation of soft-matter in its native environment is complex and not well understood. Ablation and modification thresholds for successive laser shots were obtained. The ablation craters revealed 3D nanostructures and polarization dependent orientation. The interaction also induced localized porosity in PMMA that can be controlled.

Guay, Jean-Michel

298

Reassignment of Scattered Emission Photons in Multifocal Multiphoton Microscopy  

PubMed Central

Multifocal multiphoton microscopy (MMM) achieves fast imaging by simultaneously scanning multiple foci across different regions of specimen. The use of imaging detectors in MMM, such as CCD or CMOS, results in degradation of image signal-to-noise-ratio (SNR) due to the scattering of emitted photons. SNR can be partly recovered using multianode photomultiplier tubes (MAPMT). In this design, however, emission photons scattered to neighbor anodes are encoded by the foci scan location resulting in ghost images. The crosstalk between different anodes is currently measured a priori, which is cumbersome as it depends specimen properties. Here, we present the photon reassignment method for MMM, established based on the maximum likelihood (ML) estimation, for quantification of crosstalk between the anodes of MAPMT without a priori measurement. The method provides the reassignment of the photons generated by the ghost images to the original spatial location thus increases the SNR of the final reconstructed image. PMID:24898470

Cha, Jae Won; Singh, Vijay Raj; Kim, Ki Hean; Subramanian, Jaichandar; Peng, Qiwen; Yu, Hanry; Nedivi, Elly; So, Peter T. C.

2014-01-01

299

In vivo multiphoton imaging of bile duct ligation  

NASA Astrophysics Data System (ADS)

Bile is the exocrine secretion of liver and synthesized by hepatocytes. It is drained into duodenum for the function of digestion or drained into gallbladder for of storage. Bile duct obstruction is a blockage in the tubes that carry bile to the gallbladder and small intestine. However, Bile duct ligation results in the changes of bile acids in serum, liver, urine, and feces1, 2. In this work, we demonstrate a novel technique to image this pathological condition by using a newly developed in vivo imaging system, which includes multiphoton microscopy and intravital hepatic imaging chamber. The images we acquired demonstrate the uptake, processing of 6-CFDA in hepatocytes and excretion of CF in the bile canaliculi. In addition to imaging, we can also measure kinetics of the green fluorescence intensity.

Liu, Yuan; Li, Feng-Chieh; Chen, Hsiao-Chin; Chang, Po-shou; Yang, Shu-Mei; Lee, Hsuan-Shu; Dong, Chen-Yuan

2008-02-01

300

Multi-photon absorption limits to heralded single photon sources  

PubMed Central

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; De Rossi, Alfredo; Combrie, Sylvain; Lehoucq, Gaelle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

2013-01-01

301

Multiscale multimodal imaging with multiphoton microscopy and optical coherence tomography.  

PubMed

A multiscale multiphoton microscopy (MPM) and optical coherence tomography (OCT) system has been developed using a sub-10 fs Ti:sapphire laser. The system performs cross-sectional OCT imaging over millimeter field-of-view and en-face high-resolution MPM imaging with submicrometer resolution from the same sample location. With fish cornea, we have demonstrated cross-sectional imaging of cornea tissue layers using OCT, and the zoom-in imaging of cells and collagen fibers in each layer using MPM. The multiscale MPM/OCT system shows the potential of a rapid coarse scan to search for abnormal regions and the subsequent fine zoom-in imaging for diagnosis. PMID:22179888

Tang, Shuo; Zhou, Yifeng; Chan, Kenny K H; Lai, Tom

2011-12-15

302

Multi-photon absorption limits to heralded single photon sources  

NASA Astrophysics Data System (ADS)

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources.

Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; de Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

2013-11-01

303

Multi-photon absorption limits to heralded single photon sources.  

PubMed

Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g((2))(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

Husko, Chad A; Clark, Alex S; Collins, Matthew J; De Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H; Krauss, Thomas F; Xiong, Chunle; Eggleton, Benjamin J

2013-01-01

304

Optimization-based wavefront sensorless adaptive optics for multiphoton microscopy.  

PubMed

Optical aberrations have detrimental effects in multiphoton microscopy. These effects can be curtailed by implementing model-based wavefront sensorless adaptive optics, which only requires the addition of a wavefront shaping device, such as a deformable mirror (DM) to an existing microscope. The aberration correction is achieved by maximizing a suitable image quality metric. We implement a model-based aberration correction algorithm in a second-harmonic microscope. The tip, tilt, and defocus aberrations are removed from the basis functions used for the control of the DM, as these aberrations induce distortions in the acquired images. We compute the parameters of a quadratic polynomial that is used to model the image quality metric directly from experimental input-output measurements. Finally, we apply the aberration correction by maximizing the image quality metric using the least-squares estimate of the unknown aberration. PMID:24977374

Antonello, Jacopo; van Werkhoven, Tim; Verhaegen, Michel; Truong, Hoa H; Keller, Christoph U; Gerritsen, Hans C

2014-06-01

305

Imaging photosensitizer distribution and pharmacology using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is a powerful tool for imaging sub- cellular distribution of luminescent compounds present in living cells. We have used this tool to study the distribution and pharmacology of photosensitizers in tissue and tissue culture. Murine hepatoma tumor cells dosed with a photosensitizer were briefly photoactivated, then imaged for periods up to several hours. Using the photosensitizer Rose Bengal with green light activation, nearly immediate photolytic release of lysosomal enzymes resulted in catastrophic cell destruction within 5 - 30 minutes. The magnitude and rapidity of this response is markedly different than that observed with other photosensitizer agents, and is consistent with in vivo studies illustrating that Rose Bengal is capable of causing extremely rapid destruction of treated tumors.

Wachter, Eric A.; Dees, Craig; Harkins, Jay; Fisher, Walter G.; Scott, Timothy

2002-05-01

306

Watching stem cells at work with a flexible multiphoton tomograph  

NASA Astrophysics Data System (ADS)

There is a high demand for non-invasive imaging techniques that allow observation of stem cells in their native environment without significant input on cell metabolism, reproduction, and behavior. Easy accessible hair follicle pluripotent stem cells in the bulge area and dermal papilla are potential sources for stem cell based therapy. It has been shown that these cells are able to generate hair, non-follicle skin cells, nerves, vessels, smooth muscles etc. and may participate in wound healing processes. We report on the finding of nestin-GFP expressing stem cells in their native niche in the bulge of the hair follicle of living mice by using high-resolution in-vivo multiphoton tomography. The 3D imaging with submicron resolution was based on two-photon induced fluorescence and second harmonic generation (SHG) of collagen. Migrating stem cells from the bulge to their microenvironment have been detected inside the skin during optical deep tissue sectioning.

Uchugonova, Aisada; Hoffmann, Robert; Weinigel, Martin; König, Karsten

2012-03-01

307

Reassignment of Scattered Emission Photons in Multifocal Multiphoton Microscopy  

NASA Astrophysics Data System (ADS)

Multifocal multiphoton microscopy (MMM) achieves fast imaging by simultaneously scanning multiple foci across different regions of specimen. The use of imaging detectors in MMM, such as CCD or CMOS, results in degradation of image signal-to-noise-ratio (SNR) due to the scattering of emitted photons. SNR can be partly recovered using multianode photomultiplier tubes (MAPMT). In this design, however, emission photons scattered to neighbor anodes are encoded by the foci scan location resulting in ghost images. The crosstalk between different anodes is currently measured a priori, which is cumbersome as it depends specimen properties. Here, we present the photon reassignment method for MMM, established based on the maximum likelihood (ML) estimation, for quantification of crosstalk between the anodes of MAPMT without a priori measurement. The method provides the reassignment of the photons generated by the ghost images to the original spatial location thus increases the SNR of the final reconstructed image.

Cha, Jae Won; Singh, Vijay Raj; Kim, Ki Hean; Subramanian, Jaichandar; Peng, Qiwen; Yu, Hanry; Nedivi, Elly; So, Peter T. C.

2014-06-01

308

Multi-photon free-space quantum key distribution system with synchronously delayed classical signals  

Microsoft Academic Search

We present a multi-photon scheme to improve the efficiency of free-space quantum key distribution system. Two essential features of free-space quantum key distribution system are its classical timing pulses and frequency tracking devices, we make use of these two features to design a new type of quantum key distribution system with multi-photon quantum signals and synchronously delayed classical signals. This

Li Yang; Lei Hu; Songhou Liu

2006-01-01

309

Free-space quantum key distribution system with multi-photon quantum signal  

Microsoft Academic Search

We present a multi-photon scheme to improve the efficiency of free-space quantum key distribution system. Two essential features of free-space quantum key distribution system are its classical timing pulses and frequency tracking devices, we make use of these two features to design a new type of quantum key distribution system with multi-photon quantum signals and synchronously delayed classical signals. This

Li Yang; Jiwu Jing

2005-01-01

310

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

311

Multifocal two-photon excitation fluorescence sampling imaging combining lifetime and spectrum resolutions  

NASA Astrophysics Data System (ADS)

Multifocal multiphoton microscopy (MMM) is a more efficient and powerful method for three-dimensional (3-D) fluorescence imaging with reduced acquisition time compared with conventional confocal and two-photon excitation fluorescence microscopy. We present a novel multifocal two-photon excitation fluorescence sampling imaging technique that is based on a specially designed streak camera and combines fluorescence lifetime and spectrum resolutions. A proof-of-principle experiment is performed on a standard fluorescent dye solution (Rhodamine 6G in ethanol), Time- and spectrum-resolved sampled fluorescence image of Rhodamine 6G is obtained in a snapshot. The reconstructed two-dimensional (2-D) fluorescence image of a prepared plant slide is also obtained by moving the sample laterally. The capability of this system capable of performing simultaneous 2-D measurements of temporal and spectral information has many potential applications, e.g., multi-well imaging and spectrally resolved multifocal multiphoton fluorescence lifetime imaging etc.

Liu, Lixin; Lin, Ziyang; Qu, Junle; Chen, Danni; Xu, Gaixia; Guo, Baoping; Niu, Hanben

2006-09-01

312

Theoretical studies of electronically excited states  

NASA Astrophysics Data System (ADS)

Time-dependent density functional theory is the most widely used quantum chemical method for studying molecules in electronically excited states. However, excited states can also be computed within Kohn-Sham density functional theory by exploitingmethods that converge the self-consistent field equations to give excited state solutions. The usefulness of single reference self-consistent field based approaches for studying excited states is demonstrated by considering the calculation of several types of spectroscopy including the infrared spectroscopy of molecules in an electronically excited state, the rovibrational spectrum of the NO-Ar complex, core electron binding energies and the emission spectroscopy of BODIPY in water.

Besley, Nicholas A.

2014-10-01

313

Exciting Pools  

ERIC Educational Resources Information Center

Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

Wright, Bradford L.

1975-01-01

314

Microvascular geometry and differential permeability in the eye during inflammation revealed with dual channel multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Microvascular permeability is a serious complication of systemic inflammation in critically ill patients; yet, no direct techniques exist to quantify this in vivo. To overcome this limitation, we investigated the use of multiphoton microscopy to evaluate fluorescent macromolecular gradients in the eye. Following the induction of systemic inflammation in a CD1 mouse, a bolus of high (250 KD FITC-dextran) and low (70 KD rhodamine-dextran) molecular weight fluorescent macromolecules was injected via the tail vein. The anesthetized mouse was positioned in such a way that different microvessels in the eye could be imaged directly using an upright microscope. The fluorophores were simultaneously excited at 840nm and a series of images including a spectral scan (480 to 680nm), an xt line scan (96 lines) and an x,y,z image stack were collected from the iris, cornea and limbal plexus at one hour intervals for four hours. A simple fluorescent gradient across the vessel wall was used as an index of microvascular permeability. In all microvessels, the LMW dye was more permeable. We found that the fluorescent gradient increased dramatically in the limbal plexus up to three hours then declined. This may indicate that circulating fluid pooled near the limbal plexus. Consistent with the thick walls and tight junctions of the iris microvessels, no significant fluorescent gradients were detected in this area. The cornea, containing a collagen filled stroma layer, was found to have both lateral and perpendicular fluorescent gradients. This work demonstrates that inflammation causes differential microvascular permeability in the mouse eye.

Bateman, Ryon M.; Hodgson, Kevin; Van Breemen, Casey; Walley, Keith R.

2006-02-01

315

Improved separation of the rare sulfur isotopes by infrared multiphoton dissociation of SF6  

NASA Astrophysics Data System (ADS)

The dissociation probabilities of32SF6 and some of34SF6 have been measured at a large number of CO2 laser lines both at room temperature and at 140 K. The longwavelength wing of this dissociation spectrum is exponential in the wavenumber. Its logarithmic slope is proportional to the inverse temperature. Selectivities are high enough at 140 K, that the photons are consumed only for the rare isotope in the case of34SF6 and nearly so for36SF6. For33SF6 further improvement of the selectivity would be desirable.

Del Bello, U.; Churakov, V.; Fuß, W.; Kompa, K. L.; Maurer, B.; Schwab, C.; Werner, L.

1987-03-01

316

Excitation Spectra and Brightness Optimization of Two-Photon Excited Probes  

PubMed Central

Two-photon probe excitation data are commonly presented as absorption cross section or molecular brightness (the detected fluorescence rate per molecule). We report two-photon molecular brightness spectra for a diverse set of organic and genetically encoded probes with an automated spectroscopic system based on fluorescence correlation spectroscopy. The two-photon action cross section can be extracted from molecular brightness measurements at low excitation intensities, while peak molecular brightness (the maximum molecular brightness with increasing excitation intensity) is measured at higher intensities at which probe photophysical effects become significant. The spectral shape of these two parameters was similar across all dye families tested. Peak molecular brightness spectra, which can be obtained rapidly and with reduced experimental complexity, can thus serve as a first-order approximation to cross-section spectra in determining optimal wavelengths for two-photon excitation, while providing additional information pertaining to probe photostability. The data shown should assist in probe choice and experimental design for multiphoton microscopy studies. Further, we show that, by the addition of a passive pulse splitter, nonlinear bleaching can be reduced—resulting in an enhancement of the fluorescence signal in fluorescence correlation spectroscopy by a factor of two. This increase in fluorescence signal, together with the observed resemblance of action cross section and peak brightness spectra, suggests higher-order photobleaching pathways for two-photon excitation. PMID:22385865

Mutze, Jorg; Iyer, Vijay; Macklin, John J.; Colonell, Jennifer; Karsh, Bill; Petrasek, Zdenek; Schwille, Petra; Looger, Loren L.; Lavis, Luke D.; Harris, Timothy D.

2012-01-01

317

Far-Infrared Magneto-Optical Studies in Germanium and Indium-Antimonide at High Intensities  

NASA Astrophysics Data System (ADS)

Observations of nonlinear magneto-optical phenomena occurring in p-type Germanium and n-type Indium Antimonide are reported. These include multi-photon ionization of impurity states, and a new observation, the magneto-photon ionization of impurity states, and a new observation, the magneto-photon drag effect. A novel source of far-infrared radiation has been used. This source uses a pulsed CO(,2) LASER to optically pump a super-radiant cell, generating light with intensities up to 100 KW/cm('2) and wavelengths from 66 (mu)m to 496 (mu)m in a pulse of 150 nanoseconds duration. The Germanium samples were doped with Gallium, which is a shallow acceptor with an ionization potential of 11 meV. At liquid Helium temperature virtually all charge carriers are bound to acceptor sites. However, the high intensity radiation unexpectedly ionizes the acceptors. This is demonstrated through measurements of photoconductivity, transmission and the photo-Hall Effect. This observation is unexpected because the photon energy is one-fourth the ionization potential. Rate equations describing sequential multiphoton excitations are in agreement with the experimental results. The intermediate states are postulated to be acceptor exciton band states. Studies of the photoexcited mobility at 496 (mu)m suggest that at non-saturating levels of photoexcitation, the primary scattering mechanism of hot holes in Germanium is by neutral impurities. A new magneto-optical effect, the magneto-photon drag effect, has been studied in both Germanium and Indium Antimonide. This is simply the absorption of momentum by free carriers, from an incident photon field. It has been found that the mechanism for this effect is different in the two materials. In Germanium, the effect occurs when carriers make optical transitions from the heavy hole band to the light hole band. Thus, the magneto-optical behavior depends heavily upon the band structure. On the other hand, a modified Drude model (independent electron) has been found to be reasonably successful in describing the effect in InSb. The inclusion of non-parabolicity and hot electron effects gives a consistent description of the experimental observations.

Leung, Michael

318

Infrared laser photolysis - A new tool for the study of prebiotic chemistry  

NASA Technical Reports Server (NTRS)

Infrared laser induced dielectric breakdown and multiphoton absorption experiments on CH4/NH3 'atmospheres' are described. It is found that HCN, a central intermediate in prebiotic chemistry, is a principal product. This, combined with the fact that dielectric breakdown appears to have much in common with ordinary electric sparks, suggests that the laser could be a useful tool in studies of prebiotic chemistry. Several possible experiments in this vein are suggested.

Davis, D. D.; Smith, G. R.; Guillory, W. A.

1980-01-01

319

In-vivo intratissue ablation by nanojoule near-infrared femtosecond laser pulses  

Microsoft Academic Search

Non-invasive intratissue ablation was performed in the cornea of living rabbits by using 80 MHz near-infrared intense nanojoule\\u000a femtosecond laser pulses. The intratissue surgical effect was induced by multiphoton absorption at a wavelength of 800 nm\\u000a and was ascertained by histological examination. Highly precise intratissue ablation was obtained with no detrimental effects\\u000a to the overlying or underlying layers. Activated keratocytes in the

Bao-Gui Wang; Iris Riemann; Harald Schubert; Karl-Juergen Halbhuber; Karsten Koenig

2007-01-01

320

Mid-Infrared Soliton and Raman Frequency Comb Generation in Silicon Microrings  

E-print Network

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; Wabnitz, Stefan

2014-01-01

321

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

322

Multiphoton imaging the disruptive nature of sulfur mustard lesions  

NASA Astrophysics Data System (ADS)

Sulfur mustard [bis-2-chloroethyl sulfide] is a vesicating agent first used as a weapon of war in WWI. It causes debilitating blisters at the epidermal-dermal junction and involves molecules that are also disrupted by junctional epidermolysis bullosa (JEB) and other blistering skin diseases. Despite its recurring use in global conflicts, there is still no completely effective treatment. We have shown by imaging human keratinocytes in cell culture and in intact epidermal tissues that the basal cells of skin contain well-organized molecules (keratins K5/K14, ?6?4 integrin, laminin 5 and ?3?1 integrin) that are early targets of sulfur mustard. Disruption and collapse of these molecules is coincident with nuclear displacement, loss of functional asymmetry, and loss of polarized mobility. The progression of this pathology precedes basal cell detachment by 8-24 h, a time equivalent to the "clinical latent phase" that defines the extant period between agent exposure and vesication. Our images indicate that disruption of adhesion-complex molecules also impairs cytoskeletal proteins and the integration of structures required for signal transduction and tissue repair. We have recently developed an optical system to test this hypothesis, i.e., to determine whether and how the early disruption of target molecules alters signal transduction. This environmentally controlled on-line system provides a nexus for real-time correlation of imaged lesions with DNA microarray analysis, and for using multiphoton microscopy to facilitate development of more effective treatment strategies.

Werrlein, Robert J.; Braue, Catherine R.; Dillman, James F.

2005-03-01

323

Singlet gradient index lens for deep in vivo multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Micro-optical probes, including gradient index (GRIN) lenses and microprisms, have expanded the range of in vivo multiphoton microscopy to reach previously inaccessible deep brain structures such as deep cortical layers and the underlying hippocampus in mice. Yet imaging with GRIN lenses has been fundamentally limited by large amounts of spherical aberration and the need to construct compound lenses that limit the field-of-view. Here, we demonstrate the use of 0.5-mm-diameter, 1.7-mm-long GRIN lens singlets with 0.6 numerical aperture in conjunction with a cover glass and a conventional microscope objective correction collar to balance spherical aberrations. The resulting system achieves a lateral resolution of 618 nm and an axial resolution of 5.5 ?m, compared to lateral and axial resolutions of ~1 ?m and ~15 ?m, respectively, for compound GRIN lenses of similar diameter. Furthermore, the GRIN lens singlets display fields-of-view in excess of 150 ?m, compared with a few tens of microns for compound GRIN lenses. The GRIN lens/cover glass combination presented here is easy to assemble and inexpensive enough for use as a disposable device, enabling ready adoption by the neuroscience community.

Murray, Teresa A.; Levene, Michael J.

2012-02-01

324

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

325

Multilepton and multiphoton signatures of supersymmetry at the LHC  

E-print Network

Motivated by the absence of any clear signal of physics beyond the Standard Model at the LHC after Run I, we discuss one possible slight hint of new physics and one non-minimal extension of the Standard Model. In the first part we provide a tentative explanation of a small excess of multilepton events, observed by the CMS collaboration, by means of a simplified model of gauge mediated supersymmetry breaking. In the second part we discuss how the standard phenomenology of gauge mediation can be significantly modified if one makes the non-minimal assumption that supersymmetry is broken in more than one hidden sector. Such multiple hidden sector models involve light neutral fermions called pseudo-goldstini and, due to the extra decay steps they induce, where soft photons are emitted, these models give rise to multiphoton plus missing energy signatures. We discuss why the existing LHC searches are poorly sensitive to these model and we propose new searches designed to probe them.

Petersson, Christoffer

2014-01-01

326

Multilepton and multiphoton signatures of supersymmetry at the LHC  

E-print Network

Motivated by the absence of any clear signal of physics beyond the Standard Model at the LHC after Run I, we discuss one possible slight hint of new physics and one non-minimal extension of the Standard Model. In the first part we provide a tentative explanation of a small excess of multilepton events, observed by the CMS collaboration, by means of a simplified model of gauge mediated supersymmetry breaking. In the second part we discuss how the standard phenomenology of gauge mediation can be significantly modified if one makes the non-minimal assumption that supersymmetry is broken in more than one hidden sector. Such multiple hidden sector models involve light neutral fermions called pseudo-goldstini and, due to the extra decay steps they induce, where soft photons are emitted, these models give rise to multiphoton plus missing energy signatures. We discuss why the existing LHC searches are poorly sensitive to these model and we propose new searches designed to probe them.

Christoffer Petersson

2014-05-22

327

Investigation of depilatory mechanism by use of multiphoton fluorescent microscopy  

NASA Astrophysics Data System (ADS)

Transdermal drug delivery provides a non-invasive route of drug administration, and can be a alternative method to oral delivery and injection. The stratum corneum (SC) of skin acts as the main barrier to transdermal drug delivery. Studies suggest that depilatory enhances permeability of drug through the epidermis. However, transdermal delivery pathway and mechanism are not completely understood. Previous studies have found that depilatory changes the keratinocytes of epidermis, and cause the protein in combination with lipid extraction of SC to become disordered. Nevertheless, those studies did not provide images of those processes. The aim of this study is to characterize the penetration enhancing effect of depilatory agent and the associated structural alterations of stratum corneum. Fresh human foreskin is treated by a depilatory agent for 10 minutes and then subjected to the treatment of fluorescent model drugs of hydrophilic rhodamine and hydrophobic rhodamine-RE. The penetration of model drugs is imaged and quantified by multiphoton microscopy. Our results showed that the penetration of both hydrophilic and hydrophobic agents can be enhanced and multifocal detachment of surface corneocytes is revealed. Nile red staining revealed, instead of a regular motar distribution of lipid around the brick of corneocytes, a disorganized and homogenized pattern of lipid distribution. We concluded that depilatory agents enhance drug penetration by disrupting both the cellular integrity of corneocytes and the regular packing of intercellular lipid of stratum corneum.

Lin, Chiao-Ying; Lee, Gie-ne; Jee, Shiou-Hwa; Dong, Chen-Yuan; Lin, Sung-Jan

2007-07-01

328

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

329

MPScope: a versatile software suite for multiphoton microscopy.  

PubMed

MPScope is a software suite to control and analyze data from custom-built multiphoton laser scanning fluorescence microscopes. The acquisition program MPScan acquires, displays and stores movies, linescans, image stacks or arbitrary regions from up to four imaging channels and up to two analog inputs, while plotting the intensity of regions of interest in real-time. Bidirectional linescans allow 256 x 256 pixel frames to be acquired at up to 10 fps with typical galvanometric scanners. A fast stack mode combines movie acquisition with continuous z-focus motion and adjustment of laser intensity for constant image brightness. Fast stacks can be automated by custom programs running in an integrated scripting environment, allowing a 1 mm(3) cortical volume to be sampled in 1 billion voxels in approximately 1 h. The analysis program MPView allows viewing of stored frames, projections, automatic detection of cells and plotting of their average intensity across frames, direct frame transfer to Matlab, AVI movie creation and file export to ImageJ. The combination of optimized code, multithreading and COM (Common Object Model) technologies enables MPScope to fully take advantage of custom-built two-photon microscopes and to simplify their realization. PMID:16621010

Nguyen, Quoc-Thang; Tsai, Philbert S; Kleinfeld, David

2006-09-30

330

Direct trabecular meshwork imaging in porcine eyes through multiphoton gonioscopy  

NASA Astrophysics Data System (ADS)

The development of technologies to characterize the ocular aqueous outflow system (AOS) is important for the understanding of the pathophysiology of glaucoma. Multiphoton microscopy (MPM) offers the advantage of high-resolution, label-free imaging with intrinsic image contrast because the emitted signals result from the specific biomolecular content of the tissue. Previous attempts to use MPM to image the murine irido-corneal region directly through the sclera have suffered from degradation in image resolution due to scattering of the focused laser light. As a result, transscleral MPM has limited ability to observe fine structures in the AOS. In this work, the porcine irido-corneal angle was successfully imaged through the transparent cornea using a gonioscopic lens to circumvent the highly scattering scleral tissue. The resulting high-resolution images allowed the detailed structures in the trabecular meshwork (TM) to be observed. Multimodal imaging by two-photon autofluorescence and second harmonic generation allowed visualization of different features in the TM without labels and without disruption of the TM or surrounding tissues. MPM gonioscopy is a promising noninvasive imaging tool for high-resolution studies of the AOS, and research continues to explore the potential for future clinical applications in humans.

Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Gibson, Emily A.; Lei, Tim C.

2013-03-01

331

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

332

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

333

Processing multi-photon state through operation on single photon: methods and applications  

E-print Network

Multi-photon states are widely applied in quantum information technology. By the methods presented in this paper, the structure of a multi-photon state in the form of multiple single photon qubit product can be mapped to a single photon qudit, which could also be in separable product with other photons. This makes the possible manipulation of such multi-photon states in the way of processing single photon states. The optical realization of unknown qubit discrimination (\\pra 76, 032301 (2007)) is simplified with the transformation methods. Another application is the construction of quantum logic gates, where the inverse transformations back to the input state spaces are also necessary. We especially show that the modified setups to implement the transformations can realize the deterministic multi-control gates (including Toffoli gate) operating directly on the products of single photon qubits.

Lin, Qing; Bergou, János A; Ren, Yuhang

2009-01-01

334

Processing multi-photon state through operation on single photon: methods and applications  

E-print Network

Multi-photon states are widely applied in quantum information technology. By the methods presented in this paper, the structure of a multi-photon state in the form of multiple single photon qubit product can be mapped to a single photon qudit, which could also be in separable product with other photons. This makes the possible manipulation of such multi-photon states in the way of processing single photon states. The optical realization of unknown qubit discrimination [B. He, J. A. Bergou, and Y.-H. Ren, Phys. Rev. A 76, 032301 (2007)] is simplified with the transformation methods. Another application is the construction of quantum logic gates, where the inverse transformations back to the input state spaces are also necessary. We especially show that the modified setups to implement the transformations can realize the deterministic multi-control gates (including Toffoli gate) operating directly on the products of single photon qubits.

Qing Lin; Bing He; János A. Bergou; Yuhang Ren

2009-09-21

335

Processing multiphoton states through operation on a single photon: Methods and applications  

SciTech Connect

Multiphoton states are widely applied in quantum information technology. By the methods presented in this paper, the structure of a multiphoton state in the form of multiple single-photon qubit products can be mapped to a single-photon qudit, which could also be in a separable product with other photons. This makes possible the manipulation of such multiphoton states by processing single-photon states. The optical realization of unknown qubit discrimination [B. He, J. A. Bergou, and Y.-H. Ren, Phys. Rev. A 76, 032301 (2007)] is simplified with the transformation methods. Another application is the construction of quantum logic gates, where the inverse transformations back to the input state spaces are also necessary. We especially show that the modified setups to implement the transformations can realize the deterministic multicontrol gates (including Toffoli gate) operating directly on the products of single-photon qubits.

Lin Qing [College of Information Science and Engineering, Huaqiao University (Xiamen), Xiamen 361021 (China); He Bing [Institute for Quantum Information Science, University of Calgary, Alberta, T2N 1N4 (Canada); Bergou, Janos A.; Ren, Yuhang [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States)

2009-10-15

336

Possibility of efficient generation of multiphoton entangled states using a one-dimensional nonlinear photonic crystal  

SciTech Connect

A rigorous quantum theory for the generation of multiphoton entangled states based on two consecutive three-frequency interactions of waves in a one-dimensional nonlinear photonic crystal is developed using the field expansion and differentiation methods. The three-photon correlation coefficient and the average photon numbers generated in the structure are calculated. All order expansion terms are included in the calculation. The generation conditions for multiphoton entangled states in such a structure are also analyzed. It is shown that the created photons in the present structures obey the super-Poisson statistics at the interacting frequencies and are in a multiparticle entangled state. This means the nonlinear photonic crystal can be applied as a highly efficient source of an entangled multiphoton for highly integrated all-optical circuits.

Dong Yunxia; Zhang Xiangdong [Department of Physics, Beijing Normal University, Beijing 100875 (China)

2010-03-15

337

A model for multiphoton absorption in dielectric materials induced by short laser pulses at moderate intensities.  

PubMed

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. PMID:23676194

Mézel, Candice; Duchateau, Guillaume; Geneste, Grégory; Siberchicot, Bruno

2013-06-12

338

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

339

Enhancement of molecular ions in mass spectrometry using an ultrashort optical pulse in multiphoton ionization.  

PubMed

The spectral domain of an ultraviolet femtosecond laser was expanded by stimulated Raman scattering/four-wave Raman mixing, and the resulting laser pulse was compressed using a pair of gratings. The pulse width was then measured using an autocorrelator comprised of a Michelson interferometer equipped with a multiphoton ionization/mass spectrometer which was used as a two-photon detector. A gas chromatograph/mass spectrometer was employed to analyze triacetone triperoxide (TATP), and the molecular ion induced by multiphoton ionization was substantially enhanced by decreasing the laser pulse width. PMID:20364824

Shimizu, Takashi; Watanabe-Ezoe, Yuka; Yamaguchi, Satoshi; Tsukatani, Hiroko; Imasaka, Tomoko; Zaitsu, Shin-Ichi; Uchimura, Tomohiro; Imasaka, Totaro

2010-05-01

340

Efficient entanglement concentration for arbitrary less-hyperentanglement multi-photon W states with linear optics  

NASA Astrophysics Data System (ADS)

We present an efficient protocol to concentrate arbitrary less-hyperentangled multi-photon W states to the maximally hyperentangled multi-photon W state with parameter-splitting method and linear optics elements. Compared with previous entanglement concentration works, the present protocol does not need two copies of partially entangled states or the ancillary single photon. Moreover, we discuss the feasibility of the setups of the protocol, concluding that the present protocol is feasible with the current technology. Thus, the protocol may be more meaningful in practical quantum information applications.

Fan, Lin-Lin; Xia, Yan; Song, Jie

2014-09-01

341

Excited Delirium  

PubMed Central

Excited (or agitated) delirium is characterized by agitation, aggression, acute distress and sudden death, often in the pre-hospital care setting. It is typically associated with the use of drugs that alter dopamine processing, hyperthermia, and, most notably, sometimes with death of the affected person in the custody of law enforcement. Subjects typically die from cardiopulmonary arrest, although the cause is debated. Unfortunately an adequate treatment plan has yet to be established, in part due to the fact that most patients die before hospital arrival. While there is still much to be discovered about the pathophysiology and treatment, it is hoped that this extensive review will provide both police and medical personnel with the information necessary to recognize and respond appropriately to excited delirium. PMID:21691475

Takeuchi, Asia; Ahern, Terence L.; Henderson, Sean O.

2011-01-01

342

Excited baryons  

SciTech Connect

The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)

Mukhopadhyay, N.C.

1986-01-01

343

Excited Delirium  

Microsoft Academic Search

Excited delirium accounts for 1% of our EDP (emotionally disturbed persons) cases and 99% of our headaches.” This comment,\\u000a made some years ago at a New York City conference of police chiefs captures the managerial and legal concerns of this entity.\\u000a Police managers are concerned because their officers are suddenly confronted with psychotic, violent persons, which sets into\\u000a motion an

Charles V. Wetli

344

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.

345

Effects of multi-electron correlation on multiphoton ionization and high-order harmonic generation of atomic and molecular systems in intense ultrashort laser fields  

NASA Astrophysics Data System (ADS)

The study of the electron correlation and quantum dynamics of many-electron atoms and molecules in the presence of intense external fields is a subject of much current importance in science and technology. While experimental breakthroughs constantly challenge theorists, the reverse is also true, with theorists suggesting new experimental paths and novel ways to reach exciting regimes where new physics can be explored. For example, we have recently developed ab initio methods and applications to study time dependent quantum dynamics of atoms and molecules which cannot be understood by traditional perturbation theories. Moreover, currently there exist no adequate methods capable of studying the dynamical role of the individual valence electron to the high-order harmonic generation (HHG) and multiphoton ionization (MPI) processes in strong fields. Such a study can provide insights regarding the detailed quantum dynamics and HHG mechanisms, as well as the optimal control of strong-field processes. To advance this strong-field atomic and molecular physics, this dissertation aims at the developing new theoretical formalisms and accurate computational methods for ab initio non-perturbative studies of atomic and molecular processes in intense laser fields. The new methods developed allow in-depth and precision studies of strong-field phenomena for multielectron systems. In this dissertation we investigate the role of electron correlation in dynamics of multielectron systems subject to strong fields. We present a time-dependent density functional theory (TDDFT), with proper asymptotic long-range potential, for nonperturbative treatment of multiphoton processes of homonuclear and heteronuclear diatomic molecules in intense ultrashort laser fields. A time-dependent two-center generalized pseudospectral method is presented for accurate and efficient treatment of the TDDFT equations in space and time. The procedure allows nonuniform and optimal spatial grid discretization of the Hamiltonian in prolate spheroidal coordinates and a split-operator scheme in the energy representation is extended for the time propagation of the individual molecular spin-orbital. The theory is applied to a detailed all-electron study of multiphoton ionization (MPI) and high-order harmonic generation (HHG) processes of N 2 and CO molecules in intense laser pulses. The results reveal intriguing and substantially different nonlinear optical response behaviors for N 2 and CO, despite the fact that CO has only a very small permanent dipole moment. In particular, we found that the MPI rate for CO is higher than that of N2. Furthermore, while laser excitation of the homonuclear N 2 molecule can generate only odd harmonics, both even and odd harmonics can be produced from the heteronuclear CO molecule. Next, we present a complex-scaling (CS)-generalized pseudospectral (GPS) method in hyperspherical coordinates (HSC) for an accurate ab initio and accurate treatment of the electron structure and quantum dynamics of two-electron systems. The six-dimensional coupled hyperspherical adiabatic-channel equations are discretized and solved efficiently and accurately by means of the GPS method. The GPS method allows non-uniform and optimal spatial discretization of the two-electron Hamiltonian in HSC with the use of only a very modest number of grid points. The procedure is applied for the precision calculation of the energies and widths of doubly-excited Rydberg resonance states as well as the ionization rates of He atoms in an external electric field. Lastly, we present a time-dependent generalized pseudospectral (TDGPS) approach in hyperspherical coordinates for fully ab initio nonperturbative treatment of multiphoton dynamics of atomic systems in intense laser fields. The laser-driven two-electron system is described by hyperspherical close coupling scheme. A novel 6D coupled time-dependent generalized pseudospectral method approach in hyperspherical coordinates are developed for single or double ionization without the use of the conventional adiabatic channels. In conc

Heslar, John Thomas

346

Fluorescence correlation spectroscopy based upon two-photon excitation  

NASA Astrophysics Data System (ADS)

Fluorescence correlation spectroscopy (FCS) is a powerful tool for measurement of biological dynamic processes. In this studying, a two-photon excitation fluorescence correlation spectroscopy (TP-FCS) system was set up depending on a part of optical block and detector of the multi-photon excitation fluorescence microscope (MPLFM). The phenomenon "photon-burst" was observed from the TP-FCS system. Meanwhile, the diffusion coefficient of rhodamine B molecule in sucrose aqueous solution was calculated. It was proved that TP-FCS is especially suited for integration into MPEFM accordingly to yield a hybride-technology with the peculiarities of the individual technique and the advantage of mutual synergistic effects. The fusion of both techniques seems to be reasonable and desirable to reduce costs.

Liu, Yafeng; Chen, Tongsheng; Luo, Qingming

2003-12-01

347

Infrared rainbow.  

PubMed

Radition in the near-infrared spectral region should produce a rainbow that is not visible to the human eye. An infrared photograph is shown which displays the primary bow, the secondary bow, and two supernumerary bows in side the primary bow. PMID:17775214

Greenler, R G

1971-09-24

348

A Method for Measuring Cerebral Blood Volume of Mouse using Multiphoton Laser Scanning Microscopy  

E-print Network

;Fem tosecond laser Scan mirrors (x,y) Z-translation Internal PMTs Filters cube red green External PMTs Biorad interface Dichroic mirrors mouse Fem tosecond laser Scan mirrors (x,y) Scan mirrors (x,y) Z-translatA Method for Measuring Cerebral Blood Volume of Mouse using Multiphoton Laser Scanning Microscopy P

Vial, Jean-Claude

349

Single-pulse multiphoton polymerization of complex structures using a digital multimirror device.  

PubMed

We present a rapid technique for the patterning of complex structures with ~2µm resolution via multiphoton polymerization, through use of a single ultrashort pulse in combination with the spatial intensity modulation possible from a digital multimirror device. Sub-micron features have been achieved through the use of ten consecutive pulses. PMID:23787672

Mills, Benjamin; Grant-Jacob, James A; Feinaeugle, Matthias; Eason, Robert W

2013-06-17

350

Volume 93, number 1 CHEWCALPHYSICS LIJ-KRS 19 November 1982 MULTIPHOTON IONIZATION PHOTOELECTRON SPECTROSCOPY  

E-print Network

m the photoelectron spectra. The typlcal background pressure IS 3- X 10m6 Torr. Electrons arc qectedVolume 93, number 1 CHEWCALPHYSICS LIJ-KRS 19 November 1982 MULTIPHOTON IONIZATION PHOTOELECTRON for the chlorobenzcnc molecule. 1. Introduction Photoelectron spectroscopy has been one of the most powerful methods

Zare, Richard N.

351

Intravital multiphoton imaging of immune responses in the mouse ear skin  

Microsoft Academic Search

Multiphoton (MP) microscopy enables the direct in vivo visualization, with high spatial and temporal resolution, of fluorescently tagged immune cells, extracellular matrix and vasculature in tissues. This approach, therefore, represents a powerful alternative to traditional methods of assessing immune cell function in the skin, which are mainly based on flow cytometry and histology. Here we provide a step-by-step protocol describing

Jackson LiangYao Li; Chi Ching Goh; Jo L Keeble; Jim S Qin; Ben Roediger; Rohit Jain; Yilin Wang; Weng Keong Chew; Wolfgang Weninger; Lai Guan Ng

2012-01-01

352

Intermediate representation formulation: An exact treatment for multiphoton absorption and dissociation in multilaser fields  

Microsoft Academic Search

The multiphoton dissociation of a diatomic molecule under multilaser fields is studied using a semiclassical description of the system. An L2 discretization of the dissociation channel is made in the framework of the optical model method. The time displacement propagator is calculated by a multistep first order Magnus treatment using an intermediate representation with respect to the laser field–molecule interaction.

Georges Jolicard; Gert Due Billing

1989-01-01

353

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

354

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

355

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 alternative approach to increase penetration depth in 3-D multiphoton microscopy imaging. It is based on the manipulation of the spherical aberration (SA) of the incident beam with an AO device while performing fast tomographic multiphoton imaging. When inducing SA, the image quality at best focus is reduced; however, better quality images are obtained from deeper planes within the sample. This is a compromise that enables registration of improved 3-D multiphoton images using nonimmersion objectives. Examples on ocular tissues and nonbiological samples providing different types of nonlinear signal are presented. The implementation of this technique in a future clinical instrument might provide a better visualization of corneal structures in living eyes.

Bueno, Juan M.; Skorsetz, Martin; Palacios, Raquel; Gualda, Emilio J.; Artal, Pablo

2014-01-01

356

Monitoring the beam flux in molecular beam epitaxy using laser multiphoton ionization  

Microsoft Academic Search

In this paper, we will describe a method using laser nonresonant multiphoton ionization to measure beam flux in molecular beam epitaxy (MBE) systems. The results were obtained in a test chamber where a focused excimer laser beam was used to photoionize a small fraction of the atomic and molecular beams. The constituents of the beams were identified by a time-of-flight

Ring-Ling Chien; Michael R. Sogard

1990-01-01

357

A SINGLE-PHOTON ON-DEMAND SOURCE WITH DECOUPLED SINGLE AND MULTIPHOTON  

E-print Network

A SINGLE-PHOTON ON-DEMAND SOURCE WITH DECOUPLED SINGLE AND MULTIPHOTON PROBABILITIES: INITIAL of a multiplexed downconversion system designed to pro- duce a single-photon on-demand source, by a multiple delay line trigger, yielding a single-photon certification of the produced photons. We discuss theoretically

Migdall, Alan

358

Coherent Microwave Rayleigh Scattering from Resonance Enhanced Multiphoton ionization in argon  

Microsoft Academic Search

Microwave scattering from a resonance enhanced multi-photon ionization (REMPI) produced plasma provides a new means for the direct, time accurate observation of the free electrons and thus a new method for high sensitivity REMPI spectroscopy of a gas and a new method for the measurement of electron formation and loss processes. The REMPI plasma acts as a coherent microwave scatterer,

Zhili Zhang; Mikhail Shneider; Richard Miles

2007-01-01

359

In vivo quantitation of rare circulating tumor cells by multiphoton intravital flow cytometry  

E-print Network

In vivo quantitation of rare circulating tumor cells by multiphoton intravital flow cytometry Wei of circulating tumor cells (CTCs) constitutes an emerg- ing tool for the diagnosis and staging of cancer, no existing technology has the sensitivity to measure the low numbers of tumor cells (

Cheng, Ji-Xin

360

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

361

Coexistence of multi-photon processes and longitudinal couplings in superconducting flux qubits  

Microsoft Academic Search

In contrast to natural atoms, the potential wells for superconducting flux qubit (SFQ) circuits can be artificially controlled. When the inversion symmetry of the potential energy is broken, it is found that the multi-photon processes can coexist in the multi-level SFQ circuits. Moreover, there are not only transverse but also longitudinal couplings between the external magnetic fields and the SFQs

Yu-xi Liu; Cheng-Xi Yang; Xiang-bin Wang

2010-01-01

362

The Multiphoton Interaction of Lambda Model Atom and Two-Mode Fields  

NASA Technical Reports Server (NTRS)

The system of two-mode fields interacting with atom by means of multiphotons is addressed, and the non-classical statistic quality of two-mode fields with interaction is discussed. Through mathematical calculation, some new rules of non-classical effects of two-mode fields which evolue with time, are established.

Liu, Tang-Kun

1996-01-01

363

OPTIMIZING MULTI-PHOTON FLUORESCENCE MICROSCOPY LIGHT COLLECTION FROM LIVING TISSUE BY NON-CONTACT TOTAL EMISSION DETECTION (epiTED)  

PubMed Central

Summary A benefit of multiphoton fluorescence microscopy is the inherent optical sectioning that occurs during excitation at the diffraction-limited spot. The scanned collection of fluorescence emission is incoherent; i.e., no real image needs to be formed on the detector plane. The nearly isotropic emission of fluorescence excited at the focal spot allows for new detection schemes that efficiently funnel all attainable photons to detector(s). We previously showed (Combs et al., 2007) that parabolic mirrors and condensers could be combined to collect the totality of solid angle around the excitation spot for tissue blocks, leading to ~8-fold signal gain. Using a similar approach, we have developed an in vivo Total Emission Detection (epiTED) instrument modified to make non-contact images from outside of living tissue. Simulations suggest that a ~4 fold enhancement may be possible (much larger with lower NA objectives than the 0.95 NA used here) with this approach depending on objective characteristics, imaging depth and the characteristics of the sample being imaged. In our initial prototype, two fold improvements were demonstrated in the mouse brain and skeletal muscle as well as the rat kidney using a variety of fluorophores and no compromise of spatial resolution. These results show this epiTED effectively doubles emission signal in vivo ; thus, it will maintain the image signal to noise ratio (SNR) at two times the scan rate or enable full scan rate at approximately 30% reduced laser power (to minimize photo-damage). PMID:21118209

Combs, Christian A.; Smirnov, Aleksandr; Chess, David; McGavern, Dorian B.; Schroeder, James L.; Riley, Jason; Kang, Silvia S.; Lugar-Hammer, Merav; Gandjbakhche, Amir; Knutson, Jay R.; Balaban, Robert S.

2012-01-01

364

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

E-print Network

in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized to the nonperturbative study of the multiphoton and ATI dynamics of a hydrogen atom exposed to intense short- wavelength

Chu, Shih-I

365

Supplementary figures Noninvasive multiphoton fluorescence microscopy resolves retinol  

E-print Network

­photon excitation of the RPE in an intact Rpe65­/­ mouse eye with different wavelengths of light. Retinosomes.1038/nm.2260 #12;5 Supplementary Figure 4. Increase of retinoid content in Rpe65­/­ mouse eye after gastric gavage with 9­cis­retinyl acetate. (a) TPM image of RPE in the intact eye of Rpe65­/­ mice before

Palczewski, Krzysztof

366

Enhancing multiphoton upconversion through energy clustering at sublattice level  

NASA Astrophysics Data System (ADS)

The applications of lanthanide-doped upconversionnanocrystals in biological imaging, photonics, photovoltaics and therapeutics have fuelled a growing demand for rational control over the emission profiles of the nanocrystals. A common strategy for tuning upconversion luminescence is to control the doping concentration of lanthanide ions. However, the phenomenon of concentration quenching of the excited state at high doping levels poses a significant constraint. Thus, the lanthanide ions have to be stringently kept at relatively low concentrations to minimize luminescence quenching. Here we describe a new class of upconversion nanocrystals adopting an orthorhombic crystallographic structure in which the lanthanide ions are distributed in arrays of tetrad clusters. Importantly, this unique arrangement enables the preservation of excitation energy within the sublattice domain and effectively minimizes the migration of excitation energy to defects, even in stoichiometric compounds with a high Yb3+ content (calculated as 98?mol%). This allows us to generate an unusual four-photon-promoted violet upconversion emission from Er3+ with an intensity that is more than eight times higher than previously reported. Our results highlight that the approach to enhancing upconversion through energy clustering at the sublattice level may provide new opportunities for light-triggered biological reactions and photodynamic therapy.

Wang, Juan; Deng, Renren; MacDonald, Mark A.; Chen, Bolei; Yuan, Jikang; Wang, Feng; Chi, Dongzhi; Andy Hor, Tzi Sum; Zhang, Peng; Liu, Guokui; Han, Yu; Liu, Xiaogang

2014-02-01

367

Multiphoton Femtosecond Control of Resonance-Mediated Generation of Short-Wavelength Coherent Broadband Radiation  

E-print Network

We introduce a new scheme for generating short-wavelength coherent broadband radiation with well-controlled spectral characteristics. It is based on shaping long-wavelength femtosecond pulse to coherently control atomic resonance-mediated (2+1) three-photon excitation to a broad far-from-resonance continuum. Here, the spectrum (central frequency and bandwidth) of deep-ultraviolet coherent broadband radiation generated in Na vapor is experimentally controlled by tuning the linear chirp we apply to the driving phase-shaped near-infrared femtosecond pulse. This is a first step in implementing the full scheme for producing shaped femtosecond pulses at wavelengths down-to the vacuum-ultraviolet range.

Rybak, Leonid; Gandman, Andrey; Shakour, Naser; Amitay, Zohar

2009-01-01

368

Partial indistinguishability theory for multi-photon experiments in multiport devices  

E-print Network

We develop a simple approach for description of multi-photon experiments with multi-port unitary linear optical devices for arbitrary (multi-photon) input and arbitrary photon detectors. The probabilities at the output of a multi-port device are expressed as a quadratic form with a non-negative definite Hermitian matrix describing partial indistinguishability of photons. In the case of input consisting of single photon or vacuum per input mode the output probabilities are expressed as an integral of the absolute value squared of the matrix permanent of a Hadamard product of network matrix and a matrix depending on spectral state of photons and spectral sensitivities of detectors. For example, zero coincidence probability condition for dissimilar detectors formulated in Phys. Rev. Lett. 110, 113603 (2013) using the matrix immanants is given in a much simpler form. We analyze a model of the Boson-Sampling computer with only partially indistinguishable single photons having Gaussian spectral function and Gaussia...

Shchesnovich, V S

2014-01-01

369

Deep inner-shell multiphoton ionization by intense x-ray free-electron laser pulses.  

PubMed

We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that Xe(n+) with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n?24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers. PMID:23679721

Fukuzawa, H; Son, S-K; Motomura, K; Mondal, S; Nagaya, K; Wada, S; Liu, X-J; Feifel, R; Tachibana, T; Ito, Y; Kimura, M; Sakai, T; Matsunami, K; Hayashita, H; Kajikawa, J; Johnsson, P; Siano, M; Kukk, E; Rudek, B; Erk, B; Foucar, L; Robert, E; Miron, C; Tono, K; Inubushi, Y; Hatsui, T; Yabashi, M; Yao, M; Santra, R; Ueda, K

2013-04-26

370

High-fidelity spatially resolved multiphoton counting for quantum imaging applications  

E-print Network

We present a method for spatially resolved multiphoton counting based on an intensified camera with the retrieval of multimode photon statistics fully accounting for non-linearities in the detection process. The scheme relies on one-time quantum tomographic calibration of the detector. Faithful, high-fidelity reconstruction of single- and two-mode statistics of multiphoton states is demonstrated for coherent states and their statistical mixtures. The results consistently exhibit classical values of Mandel and Fano parameters in contrast to raw statistics of camera photo-events. Detector operation is reliable for illumination levels up to the average of one photon per an event area, substantially higher than in previous approaches to characterize quantum statistical properties of light with spatial resolution.

Radoslaw Chrapkiewicz; Wojciech Wasilewski; Konrad Banaszek

2014-05-17

371

Improved Model of Fluorescence Recovery Expands the Application of Multiphoton Fluorescence Recovery after Photobleaching in Vivo  

PubMed Central

Abstract Multiphoton fluorescence recovery after photobleaching is a well-established microscopy technique used to measure the diffusion of macromolecules in biological systems. We have developed an improved model of the fluorescence recovery that includes the effects of convective flows within a system. We demonstrate the validity of this two-component diffusion-convection model through in vitro experimentation in systems with known diffusion coefficients and known flow speeds, and show that the diffusion-convection model broadens the applicability of the multiphoton fluorescence recovery after photobleaching technique by enabling accurate determination of the diffusion coefficient, even when significant flows are present. Additionally, we find that this model allows for simultaneous measurement of the flow speed in certain regimes. Finally, we demonstrate the effectiveness of the diffusion-convection model in vivo by measuring the diffusion coefficient and flow speed within tumor vessels of 4T1 murine mammary adenocarcinomas implanted in the dorsal skinfold chamber. PMID:19527668

Sullivan, Kelley D.; Sipprell, William H.; Brown, Edward B.; Brown, Edward B.

2009-01-01

372

Multiphoton cascade absorption in single molecule fluorescence saturation spectroscopy.  

PubMed

Saturation spectroscopy is a relevant method to investigate photophysical parameters of single fluorescent molecules. Nevertheless, the impact of a gradual increase, over a broad range, of the laser excitation on the intramolecular dynamics is not completely understood, particularly concerning their fluorescence emission (the so-called brightness). Thus, we propose a comprehensive theoretical and experimental study to interpret the unexpected evolution of the brightness with the laser power taking into account the cascade absorption of two and three photons. Furthermore, we highlight the key role played by the confocal observation volume in fluorescence saturation spectroscopy of single molecules in solution. PMID:23521543

Winckler, Pascale; Jaffiol, Rodolphe

2013-05-01

373

Nonlinear refraction and multiphoton absorption in polydiacetylenes from 1200 to 2200 nm  

Microsoft Academic Search

We report femtosecond measurements of the dispersion in the nonlinear refraction and multiphoton absorption in polydiacetylenes, specifically in PTS [polymer poly (bis para-toluene sulfonate) of 2,4-hexadiyne -1,6 diol] over the spectral range 1200 to 2200 nm. Various modifications of the Z-scan technique were used to make the measurements. The nonlinear refractive index coefficient n2 decreased monotonically with wavelength and can

Sergey Polyakov; Fumiyo Yoshino; Mingguo Liu; George Stegeman

2004-01-01

374

IR multiphoton dissociation of trichlorosilane induced by pulsed CO and NH laser radiation  

Microsoft Academic Search

The IR multiphoton dissociation of trichlorosilane (SiHCl) molecules irradiated by pulses from CO and NH lasers is studied. The dependences of dissociation yield on the frequency and energy density of laser radiation, as well as on the parent pressure of SiHCl, are determined. It is found that HCl and a solid precipitate, probably with a common chemical formula (SiCl){sub n},

V M Apatin; Vladimir B Laptev; Evgenii A Ryabov

2003-01-01

375

In situ multiphoton microscopy for monitoring femtosecond laser eye surgery in the human cornea and sclera  

Microsoft Academic Search

We present a multiphoton imaging system mounted on a microsurgery experimental set-up using a Nd:glass femtosecond laser. The system permits to induce laser incisions in human cornea and sclera and to perform nonlinear imaging during the intervention. The laser is a chirped pulse amplification (CPA) system with a regenerative amplifier delivering pulses at a wavelength of 1.06 mum, pulse durations

Karsten Plamann; Olivier Albert; Damien Giulieri; David Donate; Frank May; Jean-Marie Giraud; Jean-Marc Legeais

2005-01-01

376

Multiphoton ionization and third-harmonic generation in atoms and molecules  

SciTech Connect

We will discuss recent experiments on multiphoton ionization and third-harmonic generation in rare gases and small molecules using focused laser power densities of 10/sup 9/ to 10/sup 11/ W/cm/sup 2/. Also, some elementary experiments using vacuum ultraviolet light generated by frequency tripling in xenon and krypton will be described. These experiments include absorption and ionization studies using vacuum ultraviolet radiation as well as two-photon ionization using one vacuum ultraviolet photon and one laser photon.

Miller, J.C.; Compton, R.N.

1982-01-01

377

2010 MULTIPHOTON PROCESSES GORDON RESEARCH CONFERENCE, JUNE 6-11, 2010, TILTON, NH  

Microsoft Academic Search

The Gordon Research Conference on Multiphoton Processes will be held for the 15th time in 2010. The meeting continues to evolve as it embraces both the rapid technological and intellectual growth in the field as well as the multi-disciplinary expertise of the participants. This time the sessions will focus on: (1) Ultrafast coherent control; (2) Free-electron laser experiments and theory;

Mette Gaarde

2010-01-01

378

Infrared resonance Raman, and excitation profile studies of Os/sub 2/(O/sub 2/CCH/sub 3/)/sub 4/Cl/sub 2/ and Os/sub 2/(O/sub 2/CCD/sub 3/)/sub 4/Cl/sub 2/. The assignment of the osmium-osmium stretching vibration for a complex involving an osmium-osmium multiple bond  

SciTech Connect

Extensive Raman studies (1525-40 cm/sup /minus/1/) of Os/sub 2/(O/sub 2/CCH/sub 3/)/sub 4/Cl/sub 2/ have led to the identification of the three strong bands, /nu//sub 1/, /nu//sub 2/, and /nu//sub 3/, at 229, 393, and 292 cm/sup /minus/1/ to the key skeletal stretching modes, /nu/(OsOs), /nu/(OsO), and /nu/(OsCl), respectively. Raman spectra of the complex at resonance with the intense electronic band at /lambda//sub max/ = 383 nm lead to the development of a six-membered overtone progression in /nu//sub 1/ as well as combination band progressions in /nu//sub 1/ based upon one quantum of either /nu//sub 2/ or /nu//sub 3/. This indicates that the principal structural change attendant upon excitation to the resonant state is along the OsOs coordinate. Fourier transform infrared spectra (3500-40 cm/sup /minus/1/) have also been obtained. Acetate deuteriation provides conclusive evidence for many of the infrared and Raman band assignments. The study provides the first firm identification of /nu/(OsOs) for a multiply bonded species.

Clark, R.J.H.; Hempleman, A.J.; Tocher, D.A.

1988-08-31

379

Recoil frame photoemission in multiphoton ionization of small polyatomic molecules: photodynamics of NO2 probed by 400 nm fs pulses  

NASA Astrophysics Data System (ADS)

We report a general method for the complete analysis of the recoil frame photoelectron angular distribution (RFPAD) in n-photon dissociative ionization of small polyatomic molecules, resulting from (n - 1) bound-to-bound transitions plus one-photon ionization of a neutral excited state of the target. This method relies on the decomposition of the RFPAD in terms of the R_K^{} ( {\\chi ,\\theta _e } ) recoil frame azimuthal harmonics (RFAHs) which are the components of its Fourier expansion in ?e, where ? and ?e are the polar angles referring to the polarization axis P and the photoelectron momentum k relative to the ion fragment recoil direction, respectively, and ?e is the azimuth of k relative to P. The RFAH expansion method is illustrated by a detailed experimental and theoretical study of one-colour multiphoton dissociative and non-dissociative ionization of the NO2 molecule of C2v symmetry induced by 400 nm fs laser pulses, which involve electronic and nuclear dynamics within the pulse duration of the order of 70 fs. The reaction mechanism proposed to account for five-photon dissociative ionization of NO2 involves the role of [R*(6a1)-1] Rydberg states populated by three-photon absorption, subsequently ionized by a fourth photon into the NO2+ (X1?g+, v1,v2,v3) manifold involving autoionization of [R*(4b2)-1] Rydberg states, and linear versus bent geometry selective dissociation of NO2+ (X1?g+, v1,v2,v3) by a fifth photon. The reported calculations provide a coherent picture of the experimental findings although all features are not yet well reproduced.

Marggi Poullain, S.; Elkharrat, C.; Li, W. B.; Veyrinas, K.; Houver, J. C.; Cornaggia, C.; Rescigno, T. N.; Lucchese, R. R.; Dowek, D.

2014-06-01

380

Potential of ultraviolet wide-field imaging and multiphoton microscopy for analysis of dehydroergosterol in cellular membranes.  

PubMed

Dehydroergosterol (DHE) is an intrinsically fluorescent sterol with absorption/emission in the ultraviolet (UV) region and biophysical properties similar to those of cholesterol. We compared the potential of UV-sensitive low-light-level wide-field (UV-WF) imaging with that of multiphoton (MP) excitation microscopy to monitor DHE in living cells. Significantly reduced photobleaching in MP microscopy of DHE enabled us to acquire three-dimensional z-stacks of DHE-stained cells and to obtain high-resolution maps of DHE in surface ruffles, nanotubes, and the apical membrane of epithelial cells. We found that the lateral resolution of MP microscopy is ?1.5-fold higher than that of UV-WF deconvolution microscopy, allowing for improved spatiotemporal analysis of plasma membrane sterol distribution. Surface intensity patterns of DHE with a diameter of 0.2 ?m persisting over several minutes could be resolved by MP time-lapse microscopy. Diffusion coefficients of 0.25-?m-diameter endocytic vesicles containing DHE were determined by MP spatiotemporal image correlation spectroscopy. The requirement of extremely high laser power for visualization of DHE by MP microscopy made this method less potent for multicolor applications with organelle markers like green fluorescent protein-tagged proteins. The signal-to-noise ratio obtainable by UV-WF imaging could be significantly improved by pixelwise bleach rate fitting and calculation of an amplitude image from the decay model and by frame averaging after pixelwise bleaching correction of the image stacks. We conclude that UV-WF imaging and MP microscopy of DHE provide complementary information regarding membrane distribution and intracellular targeting of sterols. PMID:21181715

Wüstner, Daniel; Brewer, Jonathan R; Bagatolli, Luis; Sage, Daniel

2011-01-01

381

Infrared Thermometer  

NASA Technical Reports Server (NTRS)

Diatek Corporation, San Diego, CA and the Jet Propulsion Lab developed the Diatek Model 7000 aural thermometer which weighs only eight ounces, and measures temperature in less than two seconds using infrared astronomy technology to measure the amount of infrared energy emitted by the eardrum (the same way temperature of stars and planets is measured). This method avoids contact with mucous membranes, virtually eliminating the possibility of cross infection, and permits temperature measurement of newborn, critically ill, or incapacitated patients. Diatek Corporation was purchased by Welch Allyn Inc. The Diatek Model 7000 is now marketed as SureTemp.

1991-01-01

382

IR excitation of contaminant water by oxygen for the space shuttle at low Earth orbit altitude  

Microsoft Academic Search

As the water outgas of a space shuttle passes through the rarefied atmosphere at orbital altitude, collisions occur between the gases with sufficient energy to excite infrared-active water molecules to various vibrational and rotational states. An infrared contaminant model (IR model) has been developed to study the shuttle-induced excitation and emission of water molecules outgassed from the space shuttle. The

D. K. Zhou; W. R. Pendleton Jr.; G. E. Bingham; D. C. Thompson; W. J. Raitt; R. M. Nadile

1994-01-01

383

Investigation of the mechanism of transdermal penetration enhancer: a comparison of multiphoton microscopy and electron microscopy  

NASA Astrophysics Data System (ADS)

The aim of this study is to characterize the ability of multiphoton microscopy in monitoring the transdermal penetration enhancing effect of a depilatory agent and the associated structural alterations of stratum corneum. The result is compared with the electron microscopic findings. Our results show that the penetration of both hydrophilic and hydrophobic agents can be enhanced. The morphology of corneocytes becomes a homogenized pattern with focal detachment of surface corneocytes. In combination with Nile red staining, multiphoton imaging also shows that the regular motar-like distribution of lipid matrix was disrupted into a homogenized pattern of lipid distribution. These results are well correlated with the findings of ultrastructural analysis by electron micrographs showing disintegration of the protein envelope of coenocytes, disruption of intracellular keratin and loss of the regular lamellar packing of intercellular lipids. We conclude that, in addition to quantifying the permeation profiles of model drugs, multiphoton microscopy is able to detect the penetration enhancer-induced structural alterations of stratum corneum.

Lin, Sung-Jan; Lee, Jin-Ning; Lin, Chiao-Ying; Chan, Chih-Chieh; Lin, Ming-Gu; Wang, Chun-Chin; Tan, Hsin-Yuan; Tsai, Tsung-Hua; Jee, Shiou-Hwa; Dong, Chen-Yuan

2008-02-01

384

Infrared Spectroscopy  

NSDL National Science Digital Library

This 38-page PDF document is a chapter from the Handbook of Instrumental Techniques for Analytical Chemistry. The chapter explains how infrared spectroscopy works (no comma) along with its general uses, common applications, range and limitations. Also included are spectrometer designs, information about sample preparation, analytical methods, related methods such as gas chromotography and diffuse reflectance, and costs and instrument vendors.

Hsu, C. P.; Hall, Prentice

385

Infrared Thermometers  

ERIC Educational Resources Information Center

An infrared (IR) thermometer lab offers the opportunity to give science students a chance to measure surface temperatures, utilizing off-the-shelf technology. Potential areas of study include astronomy (exoplanets), electromagnetic spectrum, chemistry, evaporation rates, anatomy, crystal formation, and water or liquids. This article presents one…

Schaefers, John

2006-01-01

386

Femtosecond laser nanomachining initiated by ultraviolet multiphoton ionization.  

PubMed

We report on the experimental results of 300 nm features generated on fused silica using a near-infrared (IR) femtosecond laser pulse initiated by an ultraviolet (UV) pulse. With both pulses at a short (~60 fs) delay, the damage threshold of the UV pulse is only 10% of its normal value. Considerable reduction of UV damage threshold is observed when two pulses are at ± 1.3 ps delay. The damage feature size of the combined pulses is similar to that of a single UV pulse. A modified rate equation model with the consideration of defect states is used to help explain these results. This concept can be applied to shorter wavelengths, e.g. XUV and X-ray, with the required fluence below their normal threshold. PMID:24104328

Yu, Xiaoming; Bian, Qiumei; Chang, Zenghu; Corkum, P B; Lei, Shuting

2013-10-01

387

Far-Infrared Spectroscopy of Cationic Polycyclic Aromatic Hydrocarbons: Zero Kinetic Energy Photoelectron Spectroscopy of Pentacene Vaporized from Laser Desorption  

NASA Astrophysics Data System (ADS)

The distinctive set of infrared (IR) emission bands at 3.3, 6.2, 7.7, 8.6, and 11.3 ?m are ubiquitously seen in a wide variety of astrophysical environments. They are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. However, not a single PAH species has yet been identified in space, as the mid-IR vibrational bands are mostly representative of functional groups and thus do not allow one to fingerprint individual PAH molecules. In contrast, the far-IR (FIR) bands are sensitive to the skeletal characteristics of a molecule, hence they are important for chemical identification of unknown species. With an aim to offer laboratory astrophysical data for the Herschel Space Observatory, Stratospheric Observatory for Infrared Astronomy, and similar future space missions, in this work we report neutral and cation FIR spectroscopy of pentacene (C22H14), a five-ring PAH molecule. We report three IR active modes of cationic pentacene at 53.3, 84.8, and 266 ?m that may be detectable by space missions such as the SAFARI instrument on board SPICA. In the experiment, pentacene is vaporized from a laser desorption source and cooled by a supersonic argon beam. We have obtained results from two-color resonantly enhanced multiphoton ionization and two-color zero kinetic energy photoelectron (ZEKE) spectroscopy. Several skeletal vibrational modes of the first electronically excited state of the neutral species and those of the cation are assigned, with the aid of ab initio and density functional calculations. Although ZEKE is governed by the Franck-Condon principle different from direct IR absorption or emission, vibronic coupling in the long ribbon-like molecule results in the observation of a few IR active modes. Within the experimental resolution of ~7 cm-1, the frequency values from our calculation agree with the experiment for the cation, but differ for the electronically excited intermediate state. Consequently, modeling of the intensity distribution is difficult and may require explicit inclusion of vibronic interactions.

Zhang, Jie; Han, Fangyuan; Pei, Linsen; Kong, Wei; Li, Aigen

2010-05-01

388

FAR-INFRARED SPECTROSCOPY OF CATIONIC POLYCYCLIC AROMATIC HYDROCARBONS: ZERO KINETIC ENERGY PHOTOELECTRON SPECTROSCOPY OF PENTACENE VAPORIZED FROM LASER DESORPTION  

SciTech Connect

The distinctive set of infrared (IR) emission bands at 3.3, 6.2, 7.7, 8.6, and 11.3 {mu}m are ubiquitously seen in a wide variety of astrophysical environments. They are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. However, not a single PAH species has yet been identified in space, as the mid-IR vibrational bands are mostly representative of functional groups and thus do not allow one to fingerprint individual PAH molecules. In contrast, the far-IR (FIR) bands are sensitive to the skeletal characteristics of a molecule, hence they are important for chemical identification of unknown species. With an aim to offer laboratory astrophysical data for the Herschel Space Observatory, Stratospheric Observatory for Infrared Astronomy, and similar future space missions, in this work we report neutral and cation FIR spectroscopy of pentacene (C{sub 22}H{sub 14}), a five-ring PAH molecule. We report three IR active modes of cationic pentacene at 53.3, 84.8, and 266 {mu}m that may be detectable by space missions such as the SAFARI instrument on board SPICA. In the experiment, pentacene is vaporized from a laser desorption source and cooled by a supersonic argon beam. We have obtained results from two-color resonantly enhanced multiphoton ionization and two-color zero kinetic energy photoelectron (ZEKE) spectroscopy. Several skeletal vibrational modes of the first electronically excited state of the neutral species and those of the cation are assigned, with the aid of ab initio and density functional calculations. Although ZEKE is governed by the Franck-Condon principle different from direct IR absorption or emission, vibronic coupling in the long ribbon-like molecule results in the observation of a few IR active modes. Within the experimental resolution of {approx}7 cm{sup -1}, the frequency values from our calculation agree with the experiment for the cation, but differ for the electronically excited intermediate state. Consequently, modeling of the intensity distribution is difficult and may require explicit inclusion of vibronic interactions.

Zhang Jie; Han Fangyuan; Pei Linsen; Kong Wei [Department of Chemistry, Oregon State University, Corvallis, OR 97331 (United States); Li Aigen, E-mail: Wei.Kong@oregonstate.ed [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States)

2010-05-20

389

Multiphoton laser ionization for energy conversion in barium vapor  

NASA Astrophysics Data System (ADS)

We have studied the ion detection of barium atoms in special heated ovens with a tungsten rod in the middle of the stainless steel tube. The tungsten rod was heated indirectly by the oven body heaters. A bias voltage between the cell body and the tungsten rod of 9 V was used to collect electrons, after the barium ions had been created. However, we could collect the electrons even without the bias voltage, although with ten times less efficiency. We studied the conditions for the successful bias-less thermionic signal detection using excimer/dye laser two-photon excitation of Rydberg states below and above the first ionization limit (two-photon wavelength at 475.79 nm). We employed a hot-pipe oven and heat-pipe oven (with inserted mesh) in order to generate different barium vapor distributions inside the oven. The thermionic signal increased by a factor of two under heat-pipe oven conditions.

Makdisi, Y.; Kokaj, J.; Afrousheh, K.; Mathew, J.; Nair, R.; Pichler, G.

2013-03-01

390

Infrared backscattering  

NASA Technical Reports Server (NTRS)

All particles in the atmosphere are not spherical. Moreover, the scattering properties of randomly oriented nonspherical particles are not equivalent to those of spherical particles no matter how the term equivalent is defined. This is especially true for scattering in the backward direction and at the infrared wavelengths at which some atmospheric particles have strong absorption bands. Thus calculations based on Mie theory of infrared backscattering by dry or insoluble atmospheric particles are suspect. To support this assertion, it was noted that peaks in laboratory-measured infrared backscattering spectra show appreciable shifts compared with those calculated using Mie theory. One example is ammonium sulfate. Some success was had in modeling backscattering spectra of ammonium sulfate particles using a simple statistical theory called the continuous distribution of ellipsoids (CDE) theory. In this theory, the scattering properties of an ensemble are calculated. Recently a modified version of this theory was applied to measured spectra of scattering by kaolin particles. The particles were platelike, so the probability distribution of ellipsoidal shapes was chosen to reflect this. As with ammonium sulfate, the wavelength of measured peak backscattering is shifted longward of that predicted by Mie theory.

Bohren, Craig F.; Nevitt, Timothy J.; Singham, Shermila Brito

1989-01-01

391

Plasmonic enhanced quantum well infrared photodetector with high detectivity  

E-print Network

Plasmonic enhanced quantum well infrared photodetector with high detectivity Wei Wu,a Alireza-incident quantum well infrared photodetector QWIP strongly coupled with surface plasmon modes. A periodic hole-incident electromagnetic waves into surface plasmon waves, and to excite the intersubband transition of carriers

Mohseni, Hooman

392

Far infrared supplement: Catalog of infrared observations  

NASA Technical Reports Server (NTRS)

The Far Infrared Supplement: catalog of infrared observations summarizes all infrared astronomical observations at far infrared wavelengths published in the scientific literature between 1965 and 1982. The Supplement list contains 25% of the observations in the full catalog of infrared observations (C10), and essentially eliminates most visible stars from the listings. The Supplement is more compact than the main Catalog (it does not contain the bibliography and position index of the C10), and is intended for easy reference during astronomical observations.

Gezari, D. Y.; Schmitz, M.; Mead, J. M.

1984-01-01

393

In situ multiphoton microscopy for monitoring femtosecond laser eye surgery in the human cornea and sclera  

NASA Astrophysics Data System (ADS)

We present a multiphoton imaging system mounted on a microsurgery experimental set-up using a Nd:glass femtosecond laser. The system permits to induce laser incisions in human cornea and sclera and to perform nonlinear imaging during the intervention. The laser is a chirped pulse amplification (CPA) system with a regenerative amplifier delivering pulses at a wavelength of 1.06 ?m, pulse durations of 400 fs and a maximum energy of 60 ?J at repetition rates up to 10 kHz. The delivery system provides spot sizes down to the micron range. The samples are human corneas retracted from the transplant circuit mounted on a moveable anterior chamber system. Photons generated by non-linear processes in the cornea travel backwards through the beam delivery optics and are captured by a photomultiplier tube behind a dichroic mirror. The signal is filtered by a lock-in amplifier tuned to the laser repetition rate. Scanning the sample permits the acquisition of three-dimensional microscopic images. Above the incision threshold the set-up permits to induce laser cuts in human cornea following complex geometries. Below the threshold the laser pulses create secondary photons by the stimulation of non-linear optical processes in the samples which could be identified as being predominantly second harmonic generation (SHG). The in situ images obtained from the multi-photon module permit to control and optimise the surgical intervention. The combination of multiphoton imaging and corneal surgery necessitates only minimal modifications of the optical system of a femtosecond surgical laser system. A combined system significantly improves parameter control and permits the monitoring of the surgical procedure.

Plamann, Karsten; Albert, Olivier; Giulieri, Damien; Donate, David; May, Frank; Giraud, Jean-Marie; Legeais, Jean-Marc

2005-08-01

394

In vivo imaging of unstained tissues using long gradient index lens multiphoton endoscopic systems  

PubMed Central

We characterize long (up to 285 mm) gradient index (GRIN) lens endoscope systems for multiphoton imaging. We fabricate a portable, rigid endoscope system suitable for imaging unstained tissues, potentially deep within the body, using a GRIN lens system of 1 mm diameter and 8 cm length. The portable device is capable of imaging a ~200 µm diameter field of view at 4 frames/s. The lateral and axial resolution in water is 0.85 µm and 7.4 µm respectively. In vivo images of unstained tissues in live, anesthetized rats using the portable device are presented. These results show great promise for GRIN endoscopy to be used clinically. PMID:22567597

Huland, David M.; Brown, Christopher M.; Howard, Scott S.; Ouzounov, Dimitre G.; Pavlova, Ina; Wang, Ke; Rivera, David R.; Webb, Watt W.; Xu, Chris

2012-01-01

395

Alignment Dependent Enhancement of the Photoelectron Cutoff for Multiphoton Ionization of Molecules  

NASA Astrophysics Data System (ADS)

The multiphoton ionization rate of molecules depends on the alignment of the molecular axis with respect to the ionizing laser polarization. By studying molecular frame photoelectron angular distributions from N2, O2, and benzene, we illustrate how the angle-dependent ionization rate affects the photoelectron cutoff energy. We find alignment can enhance the high energy cutoff of the photoelectron spectrum when probing along a nodal plane or when ionization is otherwise suppressed. This is supported by calculations using a tunneling model with a single ion state.

Smeenk, C. T. L.; Arissian, L.; Sokolov, A. V.; Spanner, M.; Lee, K. F.; Staudte, A.; Villeneuve, D. M.; Corkum, P. B.

2014-06-01

396

Quantitative analysis on collagen morphology in aging skin based on multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy was employed for monitoring the structure changes of mouse dermis collagen in the intrinsic- or the extrinsic-age-related processes in vivo. The characteristics of textures in different aging skins were uncovered by fast Fourier transform in which the orientation index and bundle packing of collagen were quantitatively analyzed. Some significant differences in collagen-related changes are found in different aging skins, which can be good indicators for the statuses of aging skins. The results are valuable to the study of aging skin and also of interest to biomedical photonics.

Wu, Shulian; Li, Hui; Yang, Hongqin; Zhang, Xiaoman; Li, Zhifang; Xu, Shufei

2011-04-01

397

Stereoscopic visualization and quantification of auricular cartilage regeneration in rabbits using multiphoton microscopy.  

PubMed

Multiphoton microscopy (MPM) was applied for imaging and quantifying the elastic cartilage regeneration tissue in a rabbit ear model without using labeling agents. Morphology of cells and collagen matrix were analysis, showing significant difference between regenerated and intact cartilage in cellular size and collagen distribution. The results demonstrate that high resolution images provide by MPM are consistent with the histological results, and show additional biological behavior which is not visible in standard histology. Advantages in instrumentation may lead to the application of MPM for intravital detection and treatment. SCANNING 36:540-546, 2014. © 2014 Wiley Periodicals, Inc. PMID:25195587

Chen, Jing; Zhu, Xiaoqin; Xu, Yahao; Tang, Yiyan; Xiong, Shuyuan; Zhuo, Shuangmu; Chen, Jianxin

2014-09-01

398

Multiphoton imaging to distinguish grana and starch inside an intact leaf  

NASA Astrophysics Data System (ADS)

We have demonstrated a straightforward and noninvasive method to identify the distribution of grana and starch within an intact leaf. Grana and starch are the major functional structures for photosynthesis and energy storage of plant, respectively. Both exhibit highly ordered molecular structures and appear as micrometer-sized granules inside chloroplasts. In order to distinguish grana and starch, we used multiphoton microscopy, with simultaneous acquisition of two photon fluorescence (2PF) and second harmonic generation (SHG) signals. Consequently, SHG is found on both grana and starch while 2PF from chlorophyll indicates the identity of grana.

Chen, Mei-Yu; Zhuo, Guan-Yu; Chen, Po-Fu; Wu, Pei-Chun; Liu, Tzu-Ming; Chu, Shi-Wei

2013-02-01

399

Detecting localized trace species in air using radar resonance-enhanced multi-photon ionization  

SciTech Connect

A microwave-scattering-based resonance-enhanced multi-photon ionization technique is used to detect molecular species such as NO, CO, Xe, and Ar in pure form, and for standoff detection of trace species in atmospheric pressure air. In this paper,the spectra, dynamics, and the detection limits of trace species in air are studied. We demonstrate 10 m scale standoff detection of NO, and show that the system has a linear response down to the parts in 10{sup 9} NO levels in ambient air.

Dogariu, Arthur; Miles, Richard B.

2011-02-01

400

Nonlinear Magnetoresistance Oscillations in Intensely Irradiated Two-Dimensional Electron Systems Induced by Multiphoton Processes.  

SciTech Connect

We report on magneto-oscillations in differential resistivity of a two-dimensional electron system subject to intense microwave radiation. The period of these oscillations is determined not only by microwave frequency but also by its intensity. A theoretical model based on quantum kinetics at high microwave power captures all important characteristics of this phenomenon which is strongly nonlinear in microwave intensity. Our results demonstrate a crucial role of the multiphoton processes near the cyclotron resonance and its harmonics in the presence of strong dc electric field and offer a unique way to reliably determine the intensity of microwaves acting on electrons.

Khodas, M.; Chiang, H.-S.; Hatke, A.T.; Zudov, M.A.; Vavilov, M.G.; Pfeiffer, L.N.; West, K.W.

2010-05-21

401

Manifestation of nonclassical properties of strong electromagnetic radiation in multiphoton spectroscopy  

SciTech Connect

We examine multiphoton spectroscopy of a two-level system with nonvanishing intrinsic dipole moments in a two-frequency ({Omega} and {omega}) electromagnetic field. We also consider above-threshold ionization of an electron bound by a short-range potential. There is a substantial difference between the absorption coefficient and scattering spectrum of a high-frequency photon {Omega} in the presence of a quantized (squeezed) field {omega}. The latter phenomenon furnishes information about the contribution of high-order correlation functions in the nonclassical properties of a quantized electromagnetic field. 14 refs., 2 figs.

Belousov, A.V.; Kovarskii, V.A.; Prepelitsa, O.B. [Moldovan Academy of Sciences, Kishinev (Moldova, Republic of)

1995-08-01

402

Blind frequency-resolved optical-gating pulse characterization for quantitative differential multiphoton microscopy.  

PubMed

We use a unique multifocal multiphoton microscope to directly characterize the pulse in the focal plane of a high-NA objective using second-harmonic generation frequency-resolved optical gating (FROG). Because of the nature of the optical setup, femtosecond laser pulses of orthogonal polarization states are generated in the focal plane, each acquiring a different spectral dispersion. By applying an additional constraint on the phase extraction algorithm, we simultaneously extract both the gate and probe pulses from a single spectrogram with a FROG error of 0.016. PMID:20967069

Field, Jeffrey J; Durfee, Charles G; Squier, Jeff A

2010-10-15

403

Characterization of corneal damage from Pseudomonas aeruginosa infection by the use of multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Using multiphoton autofluorescence (MAF) and second harmonic generation (SHG) microscopy, we investigate the morphology and the structure of the corneal epithelium and stroma collagen of bovine cornea following injection of Pseudomonas aeruginosa. We found that corneal epithelial cells are damaged and stromal collagen becoming increasingly autofluorescent with time. We also characterized infected cornea cultured for 0, 6, 12, and 24 h by quantitative ratiometric MAF to SHG index (MAFSI) analysis. MAFSI results show that the destruction of the stromal collagen corresponds to a decrease in SHG intensity and increase of MAF signal with time.

Chang, Yu-Lin; Chen, Wei-Liang; Lo, Wen; Chen, Shean-Jen; Tan, Hsin-Yuan; Dong, Chen-Yuan

2010-11-01

404

Resonance-enhanced multiphoton ionization spectroscopy of laser-ablated copper atoms  

NASA Astrophysics Data System (ADS)

Resonance-enhanced multiphoton ionization (REMPI) spectra of laser-ablated copper atoms entrained in a supersonic free jet expansion are reported. Depending on the ionization scheme employed, and the conditions under which the copper atoms are produced, very different spectra are produced, which are discussed. In some circumstances, high proportions of metastable atoms survive the ablation and expansion process and are clearly seen in the spectra. The spectroscopic transitions for the observed lines are identified, and it is noted that some caution is merited in the assumption that only ground state copper atoms are present following laser ablation.

Andrejeva, Anna; Harris, Joe P.; Wright, Timothy G.

2014-10-01

405

Multiphoton resonances for all-optical quantum logic with multiple cavities  

NASA Astrophysics Data System (ADS)

We develop a theory for the interaction of multilevel atoms with multimode cavities yielding cavity-enhanced multiphoton resonances. The locations of the resonances are predicted from the use of effective two- and three-level Hamiltonians. As an application we show that quantum gates can be realized when photonic qubits are encoded on the cavity modes in arrangements where ancilla atoms transit the cavity. The fidelity of operations is increased by conditional measurements on the atom and by the use of a selected, dual-rail, Hilbert space. A universal set of gates is proposed, including the Fredkin gate and iswap operation; the system seems promising for scalability.

Everitt, Mark S.; Garraway, Barry M.

2014-07-01

406

Flame pumping and infrared maser action in CO2  

Microsoft Academic Search

Continuous infrared maser action has been observed in CO2 excited by purely chemical means. The methos employed, which we call chemi-optical resonant pumping, utilizes resonance radiation from molecules formed by combustion to excite other molecules isolated from the reaction.

I. Wieder

1967-01-01

407

Infrared Heaters  

NASA Technical Reports Server (NTRS)

The heating units shown in the accompanying photos are Panelbloc infrared heaters, energy savers which burn little fuel in relation to their effective heat output. Produced by Bettcher Manufacturing Corporation, Cleveland, Ohio, Panelblocs are applicable to industrial or other facilities which have ceilings more than 12 feet high, such as those pictured: at left the Bare Hills Tennis Club, Baltimore, Maryland and at right, CVA Lincoln- Mercury, Gaithersburg, Maryland. The heaters are mounted high above the floor and they radiate infrared energy downward. Panelblocs do not waste energy by warming the surrounding air. Instead, they beam invisible heat rays directly to objects which absorb the radiation- people, floors, machinery and other plant equipment. All these objects in turn re-radiate the energy to the air. A key element in the Panelbloc design is a coating applied to the aluminized steel outer surface of the heater. This coating must be corrosion resistant at high temperatures and it must have high "emissivity"-the ability of a surface to emit radiant energy. The Bettcher company formerly used a porcelain coating, but it caused a production problem. Bettcher did not have the capability to apply the material in its own plant, so the heaters had to be shipped out of state for porcelainizing, which entailed extra cost. Bettcher sought a coating which could meet the specifications yet be applied in its own facilities. The company asked The Knowledge Availability Systems Center, Pittsburgh, Pennsylvania, a NASA Industrial Applications Center (IAC), for a search of NASA's files

1979-01-01

408

Probing the spatiotemporal relationship between intracellular Ca2+ release and action potential propagation in cardiomyocytes by ultrafast multi-photon random access microscopy  

NASA Astrophysics Data System (ADS)

Action potential, via the transverse axial tubular system (TATS), synchronously triggers uniform Ca2+ release throughout the cardiomyocyte. Cardiac diseases associated with TATS structural remodeling preclude a uniform Ca2+ release across the myocyte, contributing to contractile dysfunction. A simultaneous recording of intracellular local Ca2+ release and action potential in tubular network can be useful to unravel the link between TATS abnormality and dysfunctional EC coupling. Here we combine the advantage of an ultrafast random access multi-photon (RAMP) microscope with a double staining approach to optically record AP in several TATS elements and, simultaneously, the corresponding local Ca2+ transient. Isolated rat cardiomyocytes were labeled with a novel voltage sensitive dye (VSD) and a calcium indicator. RAMP microscope rapidly scans between lines drawn across the TATS of the cardiomyocyte to perform a multiplexed measurement of the two fluorescence signals. Although the calcium and voltage indicators can be excited at the same wavelength, the large Stokes shift of the VSD emission allows us to use spectral unmixing to resolve the voltage and calcium responses. In healthy cardiomyocytes, we found uniform AP propagation within the TATS and homogeneous Ca2+ release throughout the whole cell. The capability of our technique in probing spatiotemporal relationship between Ca2+ and electrical activity was then explored in a model of acute detubulation in which failure to conduct AP in disconnected TATS may cause local delay of Ca2+ transient rise leading to non-homogenous Ca2+ release.

Sacconi, L.; Crocini, C.; Coppini, R.; Ferrantini, C.; Tesi, C.; Yan, P.; Loew, L.; Cerbai, E.; Poggesi, C.; Pavone, F. S.

2013-02-01

409

In vivo imaging of spinal cord in contusion injury model mice by multi-photon microscopy  

NASA Astrophysics Data System (ADS)

Fluorescent imaging technique is a promising method and has been developed for in vivo applications in cellular biology. In particular, nonlinear optical imaging technique, multi-photon microscopy has make it possible to analyze deep portion of tissues in living animals such as axons of spinal code. Traumatic spinal cord injuries (SCIs) are usually caused by contusion damages. Therefore, observation of spinal cord tissue after the contusion injury is necessary for understanding cellular dynamics in response to traumatic SCI and development of the treatment for traumatic SCI. Our goal is elucidation of mechanism for degeneration of axons after contusion injuries by establishing SCI model and chronic observation of injured axons in the living animals. Firstly we generated and observed acute SCI model by contusion injury. By using a multi-photon microscope, axons in dorsal cord were visualized approximately 140 micron in depth from the surface. Immediately after injury, minimal morphological change of spinal cord was observed. At 3 days after injury, spinal cord was swelling and the axons seem to be fragmented. At 7 days after injury, increased degradation of axons could be observed, although the image was blurred due to accumulation of the connective tissue. In the present study, we successfully observed axon degeneration after the contusion SCI in a living animal in vivo. Our final goal is to understand molecular mechanisms and cellular dynamics in response to traumatic SCIs in acute and chronic stage.

Oshima, Y.; Horiuchi, H.; Ogata, T.; Hikita, A.; Miura, H.; Imamura, T.

2014-03-01

410

Identification and clustering of event patterns from in vivo multiphoton optical recordings of neuronal ensembles.  

PubMed

In vivo multiphoton fluorescence microscopy allows imaging of cellular structures in brain tissue to depths of hundreds of micrometers and, when combined with the use of activity-dependent indicator dyes, opens the possibility of observing intact, functioning neural circuitry. We have developed tools for analyzing in vivo multiphoton data sets to identify responding structures and events in single cells as well as patterns of activity within the neural ensemble. Data were analyzed from populations of cerebellar Purkinje cell dendrites, which generate calcium-based complex action potentials. For image segmentation, active dendrites were identified using a correlation-based method to group covarying pixels. Firing events were extracted from dendritic fluorescence signals with a 95% detection rate and an 8% false-positive rate. Because an event that begins in one movie frame is sometimes not detected until the next frame, detection delays were compensated using a likelihood-based correction procedure. To identify groups of dendrites that tended to fire synchronously, a k-means-based procedure was developed to analyze pairwise correlations across the population. Because repeated runs of k-means often generated dissimilar clusterings, the runs were combined to determine a consensus cluster number and composition. This procedure, termed meta-k-means, gave clusterings as good as individual runs of k-means, was independent of random initial seeding, and allowed the exclusion of outliers. Our methods should be generally useful for analyzing multicellular activity recordings in a variety of brain structures. PMID:18497355

Ozden, Ilker; Lee, H Megan; Sullivan, Megan R; Wang, Samuel S-H

2008-07-01

411

Signal improvement in multiphoton microscopy by reflection with simple mirrors near the sample  

NASA Astrophysics Data System (ADS)

In conventional fluorescence or confocal microscopy, emitted light is generated not only in the focal plane but also above and below. The situation is different in multiphoton-induced fluorescence and multiphoton-induced higher harmonic generation. Here, restriction of signal generation to a single focal point permits that all emitted photons can contribute to image formation if collected, regardless of their path through the specimen. Often, the intensity of the emitted light is rather low in biological specimens. We present a method to significantly increase the fraction of photons collected by an epi (backward) detector by placing a simple mirror, an aluminum-coated coverslip, directly under the sample. Samples investigated include fluorescent test slides, collagen gels, and thin-layered, intact mouse skeletal muscles. Quantitative analysis revealed an intensity increase of second- and third-harmonic generated signal in skeletal muscle of nine- and sevenfold respectively, and of fluorescent signal in test slides of up to twofold. Our approach thus allows significant signal improvement also for situations were a forward detection is impossible, e.g., due to the anatomy of animals in intravital microscopy.

Rehberg, Markus; Krombach, Fritz; Pohl, Ulrich; Dietzel, Steffen

2010-03-01

412

Hybrid multiphoton volumetric functional imaging of large-scale bioengineered neuronal networks.  

PubMed

Planar neural networks and interfaces serve as versatile in vitro models of central nervous system physiology, but adaptations of related methods to three dimensions (3D) have met with limited success. Here, we demonstrate for the first time volumetric functional imaging in a bioengineered neural tissue growing in a transparent hydrogel with cortical cellular and synaptic densities, by introducing complementary new developments in nonlinear microscopy and neural tissue engineering. Our system uses a novel hybrid multiphoton microscope design combining a 3D scanning-line temporal-focusing subsystem and a conventional laser-scanning multiphoton microscope to provide functional and structural volumetric imaging capabilities: dense microscopic 3D sampling at tens of volumes per second of structures with mm-scale dimensions containing a network of over 1,000 developing cells with complex spontaneous activity patterns. These developments open new opportunities for large-scale neuronal interfacing and for applications of 3D engineered networks ranging from basic neuroscience to the screening of neuroactive substances. PMID:24898000

Dana, Hod; Marom, Anat; Paluch, Shir; Dvorkin, Roman; Brosh, Inbar; Shoham, Shy

2014-01-01

413

Hybrid multiphoton volumetric functional imaging of large-scale bioengineered neuronal networks  

NASA Astrophysics Data System (ADS)

Planar neural networks and interfaces serve as versatile in vitro models of central nervous system physiology, but adaptations of related methods to three dimensions (3D) have met with limited success. Here, we demonstrate for the first time volumetric functional imaging in a bioengineered neural tissue growing in a transparent hydrogel with cortical cellular and synaptic densities, by introducing complementary new developments in nonlinear microscopy and neural tissue engineering. Our system uses a novel hybrid multiphoton microscope design combining a 3D scanning-line temporal-focusing subsystem and a conventional laser-scanning multiphoton microscope to provide functional and structural volumetric imaging capabilities: dense microscopic 3D sampling at tens of volumes per second of structures with mm-scale dimensions containing a network of over 1,000 developing cells with complex spontaneous activity patterns. These developments open new opportunities for large-scale neuronal interfacing and for applications of 3D engineered networks ranging from basic neuroscience to the screening of neuroactive substances.

Dana, Hod; Marom, Anat; Paluch, Shir; Dvorkin, Roman; Brosh, Inbar; Shoham, Shy

2014-06-01

414

Preclinical study of using multiphoton microscopy to diagnose liver cancer and differentiate benign and malignant liver lesions  

NASA Astrophysics Data System (ADS)

Recently, the miniaturized multiphoton microscopy (MPM) and multiphoton probe allow the clinical use of multiphoton endoscopy for diagnosing cancer via ``optical biopsy''. The purpose of this study was to establish MPM optical diagnostic features for liver cancer and evaluate the sensitivity, specificity, and accuracy of MPM optical diagnosis. Firstly, we performed a pilot study to establish the MPM diagnostic features by investigating 60 surgical specimens, and found that high-resolution MPM images clearly demonstrated apparent differences between benign and malignant liver lesions in terms of their tissue architecture and cell morphology. Cancer cells, characterized by irregular size and shape, enlarged nuclei, and increased nuclear-cytoplasmic ratio, were identified by MPM images, which were comparable to hematoxylin-eosin staining images. Secondly, we performed a blinded study to evaluate the sensitivity, specificity, and accuracy of MPM optical diagnosis by investigating another 164 specimens, and found that the sensitivity, specificity, and accuracy of MPM diagnosis was 96.32%, 96.43%, and 96.34%, respectively. In conclusion, it is feasible to use MPM to diagnose liver cancer and differentiate benign and malignant liver lesions. This preclinical study provides the groundwork for further using multiphoton endoscopy to perform real-time noninvasive ``optical biopsy'' for liver lesions in the near future.

Yan, Jun; Zhuo, Shuangmu; Chen, Gang; Wu, Xiufeng; Zhou, Dong; Xie, Shusen; Jiang, Jiahao; Ying, Mingang; Jia, Fan; Chen, Jianxin; Zhou, Jian

2012-02-01

415

Tritium isotope separation by multiphoton dissociation of CTF/sub 3/ under CO/sub 2/-laser pulses  

SciTech Connect

Isotopic separation of tritium by CO/sub 2/ laser induced multiphoton dissociation of tritiated fluoroform is reported. It is found that maximum dissociation occurs around 1060 cm/sup -1/, that is close to the center of P branch of ..nu../sub 2/ (CTF/sub 3/). (AIP)

Mevergnies, M.N.d.; Verhoeven, F.; del Marmol, P.; Koch, G.

1982-11-01

416

Group-velocity dispersion measurements of water, seawater, and ocular components using multiphoton intrapulse interference phase scan  

Microsoft Academic Search

The use of femtosecond lasers requires accurate measurements of the dispersive properties of media. Here we measure the second- and third-order dispersion of water, seawater, and ocular components in the range of 660-930 nm using a new method known as multiphoton intrapulse interference phase scan. Our direct dispersion measurements of water have the highest precision and accuracy to date. We

Yves Coello; Bingwei Xu; Tricia L. Miller; Vadim V. Lozovoy; Marcos Dantus

2007-01-01

417

In vivo measurement of gene expression, angiogenesis and physiological function in tumors using multiphoton laser scanning microscopy  

Microsoft Academic Search

Intravital microscopy coupled with chronic animal window models has provided stunning insight into tumor pathophysiology, including gene expression, angiogenesis, cell adhesion and migration, vascular, interstitial and lymphatic transport, metabolic microenvironment and drug delivery. However, the findings to date have been limited to the tumor surface (< 150 ?m). Here, we show that the multiphoton laser-scanning microscope can provide high three-dimensional

Edward B. Brown; Robert B. Campbell; Yoshikazu Tsuzuki; Lei Xu; Peter Carmeliet; Dai Fukumura; Rakesh K. Jain

2001-01-01

418

J. Am. Chem. SOC.1994,116, 4455-4460 4455 Fragment Ion Formation in Resonance Enhanced Multiphoton  

E-print Network

,/3-d2or a,a,T,T,T-d5). Time-of-flight mass spectra of deuterated analogues of each of three conformers 18, 1994' Abstract: Resonance enhanced multiphoton ionization (REMPI) mass spectra of different impact source mass spectra. The predominant decomposition mechanism of the radical cation involves an ion

Morton, Thomas Hellman

419

Multiphoton-induced luminescence contrast between antiparallel ferroelectric domains in Mg-doped LiNbO3  

NASA Astrophysics Data System (ADS)

We report on differentiating antiparallel ferroelectric domains in congruent Mg-doped LiNbO3 (Mg:LNO) single crystals through a multiphoton photoluminescence technique. Sample illumination with femtosecond laser pulses at ? = 790 nm results in a broad multiphoton emission spectrum revealing a domain contrast of >3% between virgin and inverted domains. The contrast decreases via annealing and shows an exponential decay in the temperature range from 80 to 150 °C. Our findings give clear ground of a thermally induced structural change by surpassing a specific activation energy. Hence, the reported contrast dynamics must be closely connected to the thermal activation of charged defects, which dramatically alters the internal bias field of these defects. This explanation is also supported when using single crystal LNO of different Mg doping levels showing much lower multiphoton effects for a < 5% Mg concentration. Based on this effect of multiphoton luminescence, it becomes easy to microscopically monitor and quantify virgin and switched domains in LNO and other samples.

Reichenbach, P.; Kämpfe, T.; Thiessen, A.; Schröder, M.; Haußmann, A.; Woike, T.; Eng, L. M.

2014-06-01

420

Engineering Studies of a Pilot Plant for Laser Isotope Separation of CARBON13 by Multiphoton Dissociation of Chlorodifluoromethane  

Microsoft Academic Search

Recent research in laser isotope separation by multiphoton dissociation (LISMPD) of ^{13 }C suggests that an LISMPD commercial process is more economical than the cryogenic CO distillation technology currently used to meet most of the world's ^ {13}C demand. In this dissertation, experimental studies of an engineering process for LISMPD of polyatomic molecules is examined. The experimental results have been

Bulent Ahmet Mehmetli

1993-01-01

421

USE OF MULTIPHOTON LASER SCANNING MICROSCOPY TO IMAGE BENZO[A]PYRENE AND METABOLITES IN FISH EGGS  

EPA Science Inventory

Multiphoton laser scanning microscopy (MPLSM) is a promising tool to study the tissue distribution of environmental chemical contaminants during fish early life stages. One such chemical for which this is possible is benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon that a...

422

Highly selective population of two excited states in nonresonant two-photon absorption  

NASA Astrophysics Data System (ADS)

A nonresonant two-photon absorption process can be manipulated by tailoring the ultra-short laser pulse. In this paper, we theoretically demonstrate a highly selective population of two excited states in the nonresonant two-photon absorption process by rationally designing a spectral phase distribution. Our results show that one excited state is maximally populated while the other state population is widely tunable from zero to the maximum value. We believe that the theoretical results may play an important role in the selective population of a more complex nonlinear process comprising nonresonant two-photon absorption, such as resonance-mediated (2+1)-three-photon absorption and (2+1)-resonant multiphoton ionization.

Zhang, Hui; Zhang, Shi-An; Sun, Zhen-Rong

2011-08-01

423

Transient 2D-IR spectroscopy of inorganic excited states.  

PubMed

Time-resolved infrared spectroscopy has been proven to be a powerful tool for investigating the structure, dynamics and reactivity of electronically-excited states of inorganic molecules. As applications drive the production of ever more complex molecules however, experimental tools that can deliver more detailed spectroscopic information, or separate multiple contributions to complex signals will become increasingly valuable. In this Perspective, the extension of ultrafast infrared spectroscopy of inorganic excited states to a second frequency dimension using transient 2D-IR spectroscopy (T-2D-IR) methods is discussed. Following a brief discussion of the experimental methodologies, examples will be given of applications of T-2D-IR ranging from studies of the spectroscopy, structure and dynamics of photochemical intermediates to new tools for correlating vibrational modes in ground and excited electronic states and the investigation of excited state solvation dynamics. Future directions for these experiments are also discussed. PMID:25025224

Hunt, N T

2014-11-12

424

Two-photon excitation in scattering media by spatiotemporally shaped beams and their application in optogenetic stimulation  

PubMed Central

The use of wavefront shaping to generate extended optical excitation patterns which are confined to a predetermined volume has become commonplace on various microscopy applications. For multiphoton excitation, three-dimensional confinement can be achieved by combining the technique of temporal focusing of ultra-short pulses with different approaches for lateral light shaping, including computer generated holography or generalized phase contrast. Here we present a theoretical and experimental study on the effect of scattering on the propagation of holographic beams with and without temporal focusing. Results from fixed and acute cortical slices show that temporally focused spatial patterns are extremely robust against the effects of scattering and this permits their three-dimensionally confined excitation for depths more than 500 µm. Finally we prove the efficiency of using temporally focused holographic beams in two-photon stimulation of neurons expressing the red-shifted optogenetic channel C1V1. PMID:24409387

Begue, Aurelien; Papagiakoumou, Eirini; Leshem, Ben; Conti, Rossella; Enke, Leona; Oron, Dan; Emiliani, Valentina

2013-01-01

425

H2 excitation by magnetic shock precursors in the Cygnus Loop supernova remnant  

SciTech Connect

Emission from vibrationally excited H2 has been discovered which is associated with the bright optical shock-excited filaments to the northeast of the Cygnus Loop supernova remnant. Infrared spectroscopy and infrared and optical narrow-band images of the shock-excited gas have been obtained in an effort to understand the mechanism of H2 excitation. A shock model with a magnetic precursor is proposed which explains quantitatively the observed H2 surface brightness, level population, and relation to optical emission. A shock with a magnetic precursor can also account for some of the anomalous properties of nonradiative shocks. 64 refs.

Graham, J.R.; Wright, G.S.; Hester, J.J.; Longmore, A.J. (Palomar Observatory, Pasadena, CA (USA) Joint Astronomy Center, Hilo, HI (USA) California Institute of Technology, Pasadena (USA) Royal Observatory, Edinburgh (Scotland))

1991-01-01

426

Multi-photon UV photolysis of gaseous polycyclic aromatic hydrocarbons: Extinction spectra and dynamics  

SciTech Connect

The extinction spectra of static naphthalene and static biphenylene vapor, each buffered with a noble gas at room temperature, were measured as a function of time in the region between 390 and 850 nm after UV multi-photon laser photolysis at 308 nm. Employing incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS), the spectra were found to be unstructured with a general lack of isolated features suggesting that the extinction was not solely based on absorption but was in fact dominated by scattering from particles formed in the photolysis of the respective polycyclic aromatic hydrocarbon. Following UV multi-photon photolysis, the extinction dynamics of the static (unstirred) closed gas-phase system exhibits extraordinary quasi-periodic and complex oscillations with periods ranging from seconds to many minutes, persisting for up to several hours. Depending on buffer gas type and pressure, several types of dynamical responses could be generated (classified as types I, II, and III). They were studied as a function of temperature and chamber volume for different experimental conditions and possible explanations for the oscillations are discussed. A conclusive model for the observed phenomena has not been established. However, a number of key hypotheses have made based on the measurements in this publication: (a) Following the multi-photon UV photolysis of naphthalene (or biphenylene), particles are formed on a timescale not observable using IBBCEAS. (b) The observed temporal behavior cannot be described on basis of a chemical reaction scheme alone. (c) The pressure dependence of the system's responses is due to transport phenomena of particles in the chamber. (d) The size distribution and the refractive indices of particles are time dependent and evolve on a timescale of minutes to hours. The rate of particle coagulation, involving coalescent growth and particle agglomeration, affects the observed oscillations. (e) The walls of the chamber act as a sink. The wall conditions (which could not be quantitatively characterized) have a profound influence on the dynamics of the system and on its slow return to an equilibrium state.

Walsh, A. J.; Gash, E. W.; Mansfield, M. W. D. [Physics Department, University College Cork, Cork (Ireland)] [Physics Department, University College Cork, Cork (Ireland); Ruth, A. A. [Physics Department, University College Cork, Cork (Ireland) [Physics Department, University College Cork, Cork (Ireland); Environmental Research Institute, University College Cork, Cork (Ireland)

2013-08-07

427

Multi-photon UV photolysis of gaseous polycyclic aromatic hydrocarbons: Extinction spectra and dynamics  

NASA Astrophysics Data System (ADS)

The extinction spectra of static naphthalene and static biphenylene vapor, each buffered with a noble gas at room temperature, were measured as a function of time in the region between 390 and 850 nm after UV multi-photon laser photolysis at 308 nm. Employing incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS), the spectra were found to be unstructured with a general lack of isolated features suggesting that the extinction was not solely based on absorption but was in fact dominated by scattering from particles formed in the photolysis of the respective polycyclic aromatic hydrocarbon. Following UV multi-photon photolysis, the extinction dynamics of the static (unstirred) closed gas-phase system exhibits extraordinary quasi-periodic and complex oscillations with periods ranging from seconds to many minutes, persisting for up to several hours. Depending on buffer gas type and pressure, several types of dynamical responses could be generated (classified as types I, II, and III). They were studied as a function of temperature and chamber volume for different experimental conditions and possible explanations for the oscillations are discussed. A conclusive model for the observed phenomena has not been established. However, a number of key hypotheses have made based on the measurements in this publication: (a) Following the multi-photon UV photolysis of naphthalene (or biphenylene), particles are formed on a timescale not observable using IBBCEAS. (b) The observed temporal behavior cannot be described on basis of a chemical reaction scheme alone. (c) The pressure dependence of the system's responses is due to transport phenomena of particles in the chamber. (d) The size distribution and the refractive indices of particles are time dependent and evolve on a timescale of minutes to hours. The rate of particle coagulation, involving coalescent growth and particle agglomeration, affects the observed oscillations. (e) The walls of the chamber act as a sink. The wall conditions (which could not be quantitatively characterized) have a profound influence on the dynamics of the system and on its slow return to an equilibrium state.

Walsh, A. J.; Ruth, A. A.; Gash, E. W.; Mansfield, M. W. D.

2013-08-01

428

Multiphotonic Confocal Microscopy 3D imaging: Application to mantle sulfides in sub-arc environment (Avacha Volcano, Kamchatka)  

NASA Astrophysics Data System (ADS)

Petrogenetic relations in igneous rocks are usually studied in natural samples using classical optical microscopy and subsequent geochemical data acquisition. Multiphotonic Laser Scanning Confocal Microscopy (MLSCM) can be a powerful tool to section geological materials optically with sub-micrometric resolution and then generate a three-dimensional (3D) reconstruction (ca. 106 ?m3 stack). MLSCM is used here to investigate textural relations of Monosulfide Solid Solution (MSS) with silicate phases in fresh spinel harzburgite xenoliths from the andesitic Avacha volcano (Kamchatka, Russia). The xenoliths contain MSS disseminated in olivine and orthopyroxene (opx) neoblasts as well as MSS-rich quenched magmatic opx veins [1]. First, Reflection Mode (RM) was tested on vein sulfides in resin-impregnated thick (120 ?m) polished rock sections. Then we used a combination of Differential Interference Contrast (DIC) with a transmitted light detector, two photons-excited fluorescence (2PEF) and Second Harmonic Generation (SHG). Sequential imaging feature of the Leica TCS-SP2 software was applied. The excitation laser used for 2PEF was a COHERENT MIRA 900 with a 76Hz repetition rate and 800nm wavelength. Image stacks were analysed using ImageJ software [2]. The aim of the tests was to try to discriminate sulfides in silicate matrix as a tool for a better assessment of equilibrium conditions between the two phases. Preliminary results show that Fe-Ni rich MSS from vein and host rock have a strong auto-fluorescence in the Near UV-VIS domain (392-715 nm) whereas silicate matrix is only revealed through DIC. SHG is obtained only from dense nanocentrosymmetrical structures such as embedded medium (organic matter like glue and resin). The three images were recorded sequentially enabling efficient discrimination between the different components of the rock slices. RM permits reconstruction of the complete 3D structure of the rock slice. High resolution (ca. 0.2 ?m along X-Y axis vs. 0.4 along Z axis) 2PEF enables analysis of 3D textural relations of tiny individual MSS globules (˜10 ?m) in their various habitus. Statistical mic