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1

Photoluminescence from porous silicon by infrared multiphoton excitation  

SciTech Connect

Visible photoluminescence from porous silicon induced by infrared multiphoton excitation was observed at room temperature. Luminescence resulted from carrier excitations in the surface region of the sample. With the pump in the mid-infrared, excitation was effective only when the pump frequency was near resonance with the stretch vibrations of the surface species, SiH{sub x}. For each visible photon emitted, at least seven or eight infrared photons were absorbed. The excitation is believed to occur via pumping up a vibrational ladder, followed by conversion to electronic excitation. The process is similar to infrared multiphoton excitation of polyatomic molecules. 12 refs., 5 figs.

Chin, R.P.; Shen, Y.R. [Lawrence Berkeley Laboratory, CA (United States); Petrova-Koch, V. [Technische Universitaet Muenchen, Garching (Germany)

1995-11-03

2

Multiphoton microscopy with near infrared contrast agents  

PubMed Central

While multiphoton microscopy (MPM) has been performed with a wide range of excitation wavelengths, fluorescence emission has been limited to the visible spectrum. We introduce a paradigm for MPM of near-infrared (NIR) fluorescent molecular probes via nonlinear excitation at 1550 nm. This all-NIR system expands the range of available MPM fluorophores, virtually eliminates background autofluorescence, and allows for use of fiber-based, turnkey ultrafast lasers developed for telecommunications.

Yazdanfar, Siavash; Joo, Chulmin; Zhan, Chun; Berezin, Mikhail Y.; Akers, Walter J.; Achilefu, Samuel

2010-01-01

3

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.

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

2006-01-01

4

Infrared multiphoton electron detachment spectroscopy of C76(2-).  

PubMed

In this letter, we report the first infrared spectrum of C(76)(2-). This multiply charged anion has been studied in an electrodynamic ion trap held at room temperature using tunable infrared radiation from a free-electron laser. Resonant vibrational excitation is found to cause electron detachment and the resulting singly negatively charged as well as the remaining doubly charged parent ion are monitored as a function of IR wavelength in an experimental scheme that we term infrared multiphoton electron detachment spectroscopy. The obtained IR spectra are contrasted to computed vibrational spectra using density functional theory. The dianionic molecule retains its overall symmetry (i.e., D(2) point group) with a (1)A(1) ground state with respect to the neutral fullerene. Spectral shifts of characteristic tangential modes relative to the neutral cage are shown to originate from the excess charge density. PMID:19791880

Hampe, O; Neumaier, M; Boese, A D; Lemaire, J; Niedner-Schatteburg, G; Kappes, M M

2009-09-28

5

Multiphoton Excitation Provides Optical Sections from Deeper within Scattering Specimens than Confocal Imaging  

Microsoft Academic Search

Multiphoton excitation fluorescence imaging generates an optical section of sample by restricting fluorophore excitation to the plane of focus. High photon densities, achieved only in the focal volume of the objective, are sufficient to excite the fluorescent probe molecules by density-dependent, multiphoton excitation processes. We present comparisons of confocal with multiphoton excitation imaging of identical optical sections within a sample.

Victoria E. Centonze; John G. White

1998-01-01

6

Infrared multiphoton dissociation of two perfluorobutenes  

SciTech Connect

Photofragment translational spectroscopy was used to examine the infrared multiphoton dissociation of octafluoro-1-butene and octafluoro-2-butene. The predominant unimolecular reaction in octafluoro-1-butene at moderate laser fluences is cleavage of a carbon{endash}carbon single bond to give the products CF{sub 3} and C{sub 3}F{sub 5}. The two other reactions that take place are CF{sub 2} elimination and the formation of equal weight fragments with the chemical composition C{sub 2}F{sub 4}; both reactions take place via a diradical intermediate. Dissociation of octafluoro-1-butene to the resonance stabilized perfluoroallyl radical is suggested to account for the favoring of simple bond rupture. These three reaction pathways were also observed in octafluoro-2-butene dissociation, however, the branching fraction is different than from octafluoro-1-butene. In octafluoro-2-butene all three channels occur with roughly equal probability. The reactions involving CF{sub 2} loss and C{sub 2}F{sub 4} formation in octafluoro-2-butene are thought to proceed through the same diradical intermediate as in octafluoro-1-butene, necessitating a 1,2-fluorine migration. {copyright} {ital 1997 American Institute of Physics.}

Longfellow, C.A.; Berrie, C.L.; Suits, A.G.; Lee, Y.T. [Chemical Sciences Division, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720 (United States)] [Chemical Sciences Division, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720 (United States)

1997-11-01

7

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

8

Multiphoton excitation of organic chromophores in microbubble resonators  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

9

Dynamic photon emission from multiphoton-excited semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

The dynamic process of multiphoton optical transitions in semiconductor quantum dots (QDs) has been studied by a Monte Carlo scheme. The scheme includes optical transitions of all electrons, initially occupying the valence-band confined states in the QD, among the confined states in valence and conduction bands. The optical transition probabilities are calculated by the time-dependent Schrödinger equation, and nonradiative phonon scattering processes have been included. Assisted by a two-photon excitation by a continuous-wave laser (one photon energy equals half of the QD energy band gap), an assembly of the QDs shows an emission peak around the band gap in the optical emission spectrum, while an ultrafast pulsed laser, whose photon energy is below the QD band gap, also induces a similar narrow but weaker emission peak, which results in a nonstrict multiphoton excitation condition for many potential applications including biophotonics. Extension of the theoretical study to the spherical CdS/Cd0.5Zn0.5S/ZnS-multicoated CdSe QD has reproduced the experimental absorption and multiphoton emission spectra.

Han, T.-T.; Fu, Y.; A?Gren, H.

2008-05-01

10

Multi-photon excited luminescence of magnetic FePt core-shell nanoparticles  

PubMed Central

We present magnetic FePt nanoparticles with a hydrophilic, inert, and biocompatible silico-tungsten oxide shell. The particles can be functionalized, optically detected, and optically manipulated. To show the functionalization the fluorescent dye NOPS was bound to the FePt core-shell nanoparticles with propyl-triethoxy-silane linkers and fluorescence of the labeled particles were observed in ethanol (EtOH). In aqueous dispersion the NOPS fluorescence is quenched making them invisible using 1-photon excitation. However, we observe bright luminescence of labeled and even unlabeled magnetic core-shell nanoparticles with multi-photon excitation. Luminescence can be detected in the near ultraviolet and the full visible spectral range by near infrared multi-photon excitation. For optical manipulation, we were able to drag clusters of particles, and maybe also single particles, by a focused laser beam that acts as optical tweezers by inducing an electric dipole in the insulated metal nanoparticles. In a first application, we show that the luminescence of the core-shell nanoparticles is bright enough for in vivo multi-photon imaging in the mouse neocortex down to cortical layer 5.

Seemann, K.M.; Kuhn, B.

2014-01-01

11

Multi-photon excited luminescence of magnetic FePt core-shell nanoparticles.  

PubMed

We present magnetic FePt nanoparticles with a hydrophilic, inert, and biocompatible silico-tungsten oxide shell. The particles can be functionalized, optically detected, and optically manipulated. To show the functionalization the fluorescent dye NOPS was bound to the FePt core-shell nanoparticles with propyl-triethoxy-silane linkers and fluorescence of the labeled particles were observed in ethanol (EtOH). In aqueous dispersion the NOPS fluorescence is quenched making them invisible using 1-photon excitation. However, we observe bright luminescence of labeled and even unlabeled magnetic core-shell nanoparticles with multi-photon excitation. Luminescence can be detected in the near ultraviolet and the full visible spectral range by near infrared multi-photon excitation. For optical manipulation, we were able to drag clusters of particles, and maybe also single particles, by a focused laser beam that acts as optical tweezers by inducing an electric dipole in the insulated metal nanoparticles. In a first application, we show that the luminescence of the core-shell nanoparticles is bright enough for in vivo multi-photon imaging in the mouse neocortex down to cortical layer 5. PMID:25071977

Seemann, K M; Kuhn, B

2014-07-01

12

Electron emission from insulator and semiconductor surfaces by multiphoton excitation below the optical damage threshold  

Microsoft Academic Search

Electron emission due to 1.06 and 0.35 µm laser excitation has been measured at several pulse lengths for a number of wide bandgap semiconductors and insulators. The dependence on fluence and wavelength is consistent with multiphoton excitation across the bandgap. The work functions of the materials investigated do not appear to influence the rate-limiting multiphoton excitation process.

W. J. Siekhaus; J. H. Kinney; D. Milam; L. L. Chase

1986-01-01

13

Electron emission from insulator and semiconductor surfaces by multiphoton excitation below the optical damage threshold  

Microsoft Academic Search

Electron emission due to 1.06 and 0.35 mum laser excitation has been measured at several pulse lengths for a number of wide bandgap semiconductors and insulators. The dependence on fluence and wavelength is consistent with multiphoton excitation across the bandgap. The work functions of the materials investigated do not appear to influence the rate-limiting multiphoton excitation process.

W. J. Siekhaus; J. H. Kinney; D. Milam; L. L. Chase

1986-01-01

14

Evidence for excitation of fluorescence in RPE melanin by multiphoton absorption  

NASA Astrophysics Data System (ADS)

Previously, we reported that ultrashort, near infrared (NIR) laser pulses caused more DNA breakage in cultured retinal pigment epithelial (RPE) cells than did CW, NIR laser radiation delivering a similar radiant exposure. We hypothesized that this difference was due to multiphoton absorption in an intracellular chromophore such as the RPE melanin. We investigated two-photon excitation of fluorescence in a suspension of isolated bovine RPE melanosomes exposed to a 1-KHz train of approximately 50- fsec laser pulses at 810 nm from a Ti:Sapphire laser, and compared this to the fluorescence excited by CW exposures at 406 nm from a Krypton ion laser. Fluorescence was measured with a PC-based spectrometer. The CW sources excited fluorescence with a peak at 525 nm. The fluorescence intensity depended on the irradiance of the sample, as well as the melanosome concentration. Peak fluorescence was obtained with a suspension of ~2 x 107 melanin granules/ml. The 810-nm, ultrashort pulses also excited fluorescence, but with a broader, lower-amplitude peak. The weaker fluorescence signal excited by the 810-nm ultrashort pulse laser for a given melanosome concentration, compared to 406-nm CW excitation, is possibly due to the smaller two- photon absorption cross-section. These results indicate the involvement of multiphoton absorption in DNA damage.

Glickman, Randolph D.; Rockwell, Benjamin A.; Noojin, Gary D.; Stolarski, David J.; Denton, Michael L.

2002-06-01

15

Controlled Damage in Thick Specimens by Multiphoton ExcitationV?  

PubMed Central

Controlled damage by light energy has been a valuable tool in studies of cell function. Here, we show that the Ti:Sapphire laser in a multiphoton microscope can be used to cause localized damage within unlabeled cells or tissues at greater depths than previously possible. We show that the damage is due to a multiphoton process and made wounds as small as 1 ?m in diameter 20 ?m from the surface. A characteristic fluorescent scar allows monitoring of the damage and identifies the wound site in later observations. We were able to lesion a single axon within a bundle of nerves, locally interrupt organelle transport within one axon, cut dendrites in a zebrafish embryo, ablate a mitotic pole in a sea urchin egg, and wound the plasma membrane and nuclear envelope in starfish oocytes. The starfish nucleus collapsed ?1 h after wounding, indicating that loss of compartmentation barrier makes the structure unstable; surprisingly, the oocyte still completed meiotic divisions when exposed to maturation hormone, indicating that the compartmentalization and translocation of cdk1 and its regulators is not required for this process. Multiphoton excitation provides a new means for producing controlled damage deep within tissues or living organisms.

Galbraith, James A.; Terasaki, Mark

2003-01-01

16

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

SciTech Connect

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

Dai, H.L.

1981-04-01

17

Investigations of Multiphoton Excitation and Ionization in a Short Range Potential.  

National Technical Information Service (NTIS)

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 ...

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

1989-01-01

18

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

19

Multiphoton excitation provides optical sections from deeper within scattering specimens than confocal imaging.  

PubMed

Multiphoton excitation fluorescence imaging generates an optical section of sample by restricting fluorophore excitation to the plane of focus. High photon densities, achieved only in the focal volume of the objective, are sufficient to excite the fluorescent probe molecules by density-dependent, multiphoton excitation processes. We present comparisons of confocal with multiphoton excitation imaging of identical optical sections within a sample. These side-by-side comparisons of imaging modes demonstrate a significant advantage of multiphoton imaging; data can be obtained from deeper within biological specimens. Observations on a variety of biological samples showed that in all cases there was at least a twofold improvement in the imaging penetration depth obtained with multiphoton excitation relative to confocal imaging. The more pronounced degradation in image contrast deep within a confocally imaged sample is primarily due to scattered emission photons, which reduce the signal and increase the local background as measurements of point spread functions indicated that resolution does not significantly change with increasing depth for either mode of microscopy. Multiphoton imaging does not suffer from degradation of signal-to-background to nearly the same extent as confocal imaging because this method is insensitive to scatter of the emitted signal. Direct detection of emitted photons using an external photodetector mounted close to the objective (possible only in a multiphoton imaging system) improves system sensitivity and the utilization of scattered emission photons for imaging. We demonstrate that this technique provides yet further improvements in the capability of multiphoton excitation imaging to produce good quality images from deeper within tissue relative to confocal imaging. PMID:9746543

Centonze, V E; White, J G

1998-10-01

20

Infrared Multiphoton and Collision Induced Dissociation Studies of Some Gaseous Alkylamine Ions.  

National Technical Information Service (NTIS)

Collision induced dissociation and infrared multiphoton dissociation of ions formed in di- and triethylamine, di- and tri-n-propylamine, and diisopropylamine were investigated by Fourier transform ion cyclotron resonance mass spectrometry. Molecular ions ...

C. H. Watson G. Baykut M. A. Battiste J. R. Eyler

1986-01-01

21

Energetics from Slow Infrared Multiphoton Dissociation of Biomolecules  

PubMed Central

Photodissociation kinetics of the protonated pentapeptide leucine enkephalin measured using a cw CO2 laser and a Fourier-transform mass spectrometer are reported. A short induction period, corresponding to the time required to raise the internal energy of the ion population to a (dissociating) steady state, is observed. After this induction period, the dissociation data are accurately fit by first-order kinetics. A plot of the log of the unimolecular dissociation rate constant, kuni, as a function of the log of laser power is linear at low laser powers (<9 W, kuni <0.05 s?1), but tapers off at high laser power (9–33 W, kuni = 0.05–7 s?1). The entire measured dissociation curve can be accurately fit by an exponential function plus a constant. The experiment is simulated using a master equation formalism. In the model, the laser radiation is described as an energetically flat-topped distribution which is spatially uniform. This description is consistent with experimental results which indicate that ion motion within the cell averages out spatial inhomogeneities in the laser light. The model has several adjustable parameters. The effect of varying these parameters on the calculated kinetics and power dependence curves is discussed. A procedure for determining a limited range of threshold dissociation energy, Eo, which fits both the measured induction period and power dependence curves, is presented. Using this procedure, Eo of leucine enkephalin is determined to be 1.12–1.46 eV. This result is consistent with, although less precise than, values measured previously using blackbody infrared radiative dissociation. Although the blackbody dissociation results were used as a starting point to search for fits of the master equation model to experiment, these results demonstrate that it is, in principle, possible to determine a limited range of Eo from slow infrared multiphoton dissociation data alone.

Jockusch, Rebecca A.; Paech, Kolja

2005-01-01

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

Inclusion of discrete-to-continuum coupling in multiphoton excitation and dissociation calculations  

NASA Technical Reports Server (NTRS)

A nonperturbative approach to multiphoton excitation and dissociation of molecules is presented in which coupling to the continuum is treated explicitly. Transitions among continuum levels are not modeled directly, but something of their effect is represented by assuming that the continuum population density is so low as to be effectively zero at all times. Two trial applications are briefly discussed.

Zimmerman, I. H.; Druger, S. D.; George, T. F.

1983-01-01

24

Multiphoton Rabi oscillations between highly excited Stark states of potassium  

SciTech Connect

We have applied a nonperturbative resonant theory to study the Rabi frequency of microwave multiphoton transitions between two Rydberg states of potassium in a static electric field. The Stark electric dipole moments used to calculate the Rabi frequency are determined by the Stark states' wave functions, which are obtained by the diagonalization method. The frequencies of the Rabi oscillations are in good agreement with either experimental ones or ones calculated by the time-dependent close-coupling method and the Floquet theory. Furthermore, we are able to show that the size of avoided crossings between the (n+2)s and (n,3) states can be predicted from the Stark electric dipole moment and the difference of the two Stark states' energy at a given resonance.

He Yonglin [Department of Physics and Mechanical and Electrical Engineering, Hexi University, Zhangye Gansu 734000 (China)

2011-11-15

25

Multiphoton excitation fluorescence microscopy and spectroscopy of in vivo human skin.  

PubMed Central

Multiphoton excitation microscopy at 730 nm and 960 nm was used to image in vivo human skin autofluorescence from the surface to a depth of approximately 200 microm. The emission spectra and fluorescence lifetime images were obtained at selected locations near the surface (0-50 microm) and at deeper depths (100-150 microm) for both excitation wavelengths. Cell borders and cell nuclei were the prominent structures observed. The spectroscopic data suggest that reduced pyridine nucleotides, NAD(P)H, are the primary source of the skin autofluorescence at 730 nm excitation. With 960 nm excitation, a two-photon fluorescence emission at 520 nm indicates the presence of a variable, position-dependent intensity component of flavoprotein. A second fluorescence emission component, which starts at 425 nm, is observed with 960-nm excitation. Such fluorescence emission at wavelengths less than half the excitation wavelength suggests an excitation process involving three or more photons. This conjecture is further confirmed by the observation of the super-quadratic dependence of the fluorescence intensity on the excitation power. Further work is required to spectroscopically identify these emitting species. This study demonstrates the use of multiphoton excitation microscopy for functional imaging of the metabolic states of in vivo human skin cells. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5

Masters, B R; So, P T; Gratton, E

1997-01-01

26

Multiphoton resonant excitations and high-harmonic generation in bilayer graphene  

NASA Astrophysics Data System (ADS)

The microscopic theory of bilayer graphene nonlinear interaction with coherent electromagnetic radiation is developed. The Liouville-von Neumann equation for a single-particle density matrix in the multiphoton resonant approximation is solved. We consider low-energy excitations of a Fermi-Dirac sea with THz pump radiation. The obtained solutions disclose Rabi oscillations and resonant multiphoton excitations of a Fermi-Dirac sea in bilayer graphene. On the basis of numerical simulations we examine the rates of high-harmonic radiation at particle-hole annihilation in the field of a strong pump wave. We show that in the THz domain of frequencies one can achieve efficient generation of high harmonics with pump waves of moderate intensities.

Avetissian, H. K.; Mkrtchian, G. F.; Batrakov, K. G.; Maksimenko, S. A.; Hoffmann, A.

2013-10-01

27

Simultaneous multiple-excitation multiphoton microscopy yields increased imaging sensitivity and specificity  

Microsoft Academic Search

Background  Multiphoton microscopy (MPM) offers many advantages over conventional wide-field and confocal laser scanning microscopy (CLSM)\\u000a for imaging biological samples such as 3D resolution of excitation, reduced phototoxicity, and deeper tissue imaging. However,\\u000a adapting MPM for critical multi-color measurements presents a challenge because of the largely overlapping two-photon absorption\\u000a (TPA) peaks of common biological fluorophores. Currently, most multi-color MPM relies on

Margaret T Butko; Mikhail Drobizhev; Nikolay S Makarov; Aleksander Rebane; Brendan C Brinkman; Joseph G Gleeson

2011-01-01

28

Luminescence Enhancement from Silica-Coated Gold Nanoparticle Agglomerates Following Multi-photon Excitation  

Microsoft Academic Search

Multi-photon absorption induced luminescence (MAIL) from bare gold nanoparticles, silica-coated particles, as well as silica-coated\\u000a agglomerated gold nanoparticles suspended in aqueous solution was studied by using time-resolved and steady-state luminescence\\u000a spectroscopy. The nanoparticles were excited by femtosecond pulses of wavelengths ranging from 630 nm to 900 nm. The luminescence\\u000a from the particles exhibits a broad spectrum in the UV and VIS region.

Sviatlana Viarbitskaya; Linus Ryderfors; Therese Mikaelsson; Emad Mukhtar; Lennart B.-Å. Johansson

2011-01-01

29

Photoelectron imaging following 2 + 1 multiphoton excitation of HBr.  

PubMed

The photodissociation and photoionization dynamics of HBr via low-n Rydberg and ion-pair states was studied by using 2 + 1 REMPI spectroscopy and velocity map imaging of photoelectrons. Two-photon excitation at about 9.4-10 eV was used to prepare rotationally selected excited states. Following absorption of the third photon the unperturbed F (1)Delta(2) and i (3)Delta(2) states ionize directly into the ground vibrational state of the molecular ion according to the Franck-Condon principle and upon preservation of the ion core. In case of the V (1)Sigma(+)(0(+)) ion-pair state and the perturbed E (1)Sigma(+)(0(+)), g (3)Sigma(-)(0(+)), and H (1)Sigma(+)(0(+)) Rydberg states the absorption of the third photon additionally results in a long vibrational progression of HBr(+) in the X (2)Pi state as well as formation of electronically excited atomic photofragments. The vibrational excitation of the molecular ion is explained by autoionization of repulsive superexcited states into the ground state of the molecular ion. In contrast to HCl, the perturbed Rydberg states of HBr show strong participation of the direct ionization process, with ionic core preservation. PMID:16880906

Romanescu, Constantin; Loock, Hans-Peter

2006-07-01

30

Near-infrared femtosecond laser machining initiated by ultraviolet multiphoton ionization  

NASA Astrophysics Data System (ADS)

We report on the experimental study of microstructures fabricated on the surface of fused silica by two femtosecond laser pulses, a tightly focused 266 nm beam followed by a loosely focused 800 nm beam. By setting the fluence of each pulse below the damage threshold, visible microstructures are fabricated using the combined beams. Our results suggest that the ultraviolet pulse generates seed electrons through multiphoton absorption, and the near-infrared pulse utilizes these electrons to cause damage by avalanche ionization.

Yu, X.; Bian, Q.; Zhao, B.; Chang, Z.; Corkum, P. B.; Lei, S.

2013-03-01

31

Alternative approaches to infrared multiphoton dissociation in an external ion reservoir  

Microsoft Academic Search

In this work we present variations on in-hexapole infrared multiphoton dissociation (IRMPD) for the characterization of modified\\u000a oligonucleotides using an ESI-FTICR spectrometer. We demonstrate that IRMPD in the external ion reservoir provides a comprehensive\\u000a series of fragments allowing thorough characterization of a wide range of oligonucleotides containing alternative backbones\\u000a and 2? substitutions. An alternative pulse sequence is presented that allows

Steven A. Hofstadler; Jared J. Drader; Hans Gaus; James C. Hannis; Kristin A. Sannes-Lowery

2003-01-01

32

Microfluorometric Detection of Catecholamines with Multiphoton-Excited Fluorescence  

NASA Astrophysics Data System (ADS)

We demonstrate sensitive spatially resolved detection of physiological chromophores that emit in the ultraviolet (less than 330 nm). An atypical laser source (a visible wavelength femtosecond optical parametric oscillator), and an unconventional collection geometry (a lensless detector that detects the forward-emitted fluorescence) enable this detection. We report the excitation spectra of the catecholamines dopamine and norepinephrine, together with near-UV emitters serotonin and tryptophan, in the range of 550-595 nm. We estimate the molecular two-photon action cross section of dopamine, norepinephrine, and serotonin to be 1.2 mGM (1 GM, or Goppert Mayor, is equal to 10^-58 m^4 s^-1 photon^-1), 2 mGM, and 43 mGM, respectively, at 560 nm. The sensitivity achieved by this method holds promise for the microscopic imaging of vesicular catecholamines in live cells.

Balaji, J.; Reddy, Chandra S.; Kaushalya, S. K.; Maiti, Sudipta

2004-04-01

33

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

34

Laser-intensity dependent vibrational excitation and alignment of molecular ions in the ultrafast multiphoton regime.  

PubMed

H2 molecules were ionized in the ultrafast (approximately 150 fs) multiphoton regime (263 nm, approximately 10(13) W cm(-2)). Earlier experiments investigated the kinetic energies of electrons or ions only. Using a unique experiment, we show that the vibrational excitation of molecular ions contains essential information about the dynamics of the process. In addition, we prove some earlier interpretations wrong. A realistic model based on vibronically excited intermediates, Stark shifting into resonance, reproduces the measurements, demonstrating that resonances continue to be important in the femtosecond regime. This eventually enables ultrafast control of the vibrational excitation of molecular ions, which is relevant to the whole field of molecular physics and physical chemistry. PMID:19113546

Posthumus, J H; Fabre, B; Cornaggia, C; de Ruette, N; Urbain, X

2008-12-01

35

Freeform multiphoton excited microfabrication for biological applications using a rapid prototyping CAD-based approach  

NASA Astrophysics Data System (ADS)

Multiphoton excited polymerization has attracted increasing attention as a powerful 3 dimensional nano/microfabrication tool. The nonlinear excitation confines the fabrication region to the focal volume allowing the potential to achieve freeform fabrication with submicron capabilities. We report the adaptation and use of a computer aided design (CAD) approach, based on rapid prototyping software, which exploits this potential for fabricating with protein and polymers in biologically compatible aqueous environments. 3D structures are drawn in the STL format creating a solid model that can be sliced, where the individual sections are then serially fabricated without overwriting previous layers. The method is shown for potential biological applications including microfluidics, cell entrapment, and tissue engineering.

Cunningham, Lawrence P.; Veilleux, Matthew P.; Campagnola, Paul J.

2006-09-01

36

Infrared multiphoton and collision induced dissociation studies of some gaseous alkylamine ions  

NASA Astrophysics Data System (ADS)

Collision induced dissociation and infrared multiphoton dissociation of ions formed in di- and triethylamine, di- and tri-n-propylamine, and diisopropylamine were investigated by Fourier transform ion cyclotron resonance mass spectrometry. Molecular ions of all amines except di-n-propylamine produced similar fragment ions when subjected to either dissociation technique. The initial fragmentation involved C(alpha)-C(beta) bond cleavage, loss of an alkyl radical, and formation of an immonium ion. Subsequent fragmentations of the immonium ions produced by both dissociation mechanisms involved McLafferty type rearrangements and loss of alkenes. The molecular ion of di-n-propylamine fragmented by a different mechanism when subjected to infrared irradiation. Protonated molecules of di- and tri-n-propylamine yielded C3H6 and an ammonium ion upon infrared multiphoton dissociation, while protonated molecules of the other amines did not dissociate using this technique. Collision induced dissociation, on the other hand, produced fragmentation for all protonated molecules. Explanation of the different fragmentations observed for the two dissociation techniques is given in terms of a mechanism involving a tight transition state for protonated di- and tri-n-propylamine dissociation.

Watson, C. H.; Baykut, G.; Battiste, M. A.; Eyler, J. R.

1986-01-01

37

Optical Biopsy of In Vivo Human Skin: Multi-photon Excitation Microscopy  

Microsoft Academic Search

  Two-photon excitation microscopy has the potential as an effective, non-invasive, imaging tool for in vivo examination of\\u000a human deep tissue structure at the subcellular level. By using infrared photons as the excitation source in two-photon microscopy,\\u000a a significant improvement in penetration depth can be achieved because of the much lower tissue absorption coefficient and\\u000a reduced scattering coefficient in the infrared

B. R. Masters; P. T. C. So; E. Gratton

1998-01-01

38

Circular Dichroism and Photoelectron Angular Distributions of Excited States of Cesium and Rubidium Using Resonantly Enhanced Multiphoton Ionization Techniques  

Microsoft Academic Search

Resonantly enhanced multiphoton ionization (REMPI) techniques are used to study spin-orbit effects in the photoelectron angular distributions (PEAD) of excited ns (n = 8-13) states of cesium. The asymmetry parameters are shown to exhibit an energy dependence in the region of the Cooper minimum of the photoionization cross section, supporting predictions made by inclusion of relativistic coupling in the continuum.

Luis Edgardo Cuellar

1993-01-01

39

Visualization of nanocontractions in cardiomyocytes by simultaneous detection of second- and third- harmonic generation and multiphoton excitation fluorescence microscopy  

Microsoft Academic Search

Dynamic imaging of cardiomyocytes was performed with a simultaneous detection second harmonic generation (SHG), third harmonic generation (THG) and multiphoton excitation fluorescence (MPF) microscope. The fast scanning system of ~12 frames\\/second synchronized with multichannel detection provided the possibility of imaging three dimensional static and two dimensional dynamic structures of cardiomyocytes. The SHG images highlighted the myofibrils of the cardiomyocytes while

Catherine Greenhalgh; Virginijus Barzda; Steven Elmore; Juerg Aus der Au; Jeffrey Squier

2005-01-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2001-04-01

41

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

PubMed Central

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

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

2010-01-01

42

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

PubMed Central

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

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

2003-01-01

43

Multiphoton-excited microfabrication in live cells via Rose Bengal cross-linking of cytoplasmic proteins  

NASA Astrophysics Data System (ADS)

We demonstrate the use of multiphoton-excited photochemistry to cross-link three-dimensional matrices directly from cytoplasmic proteins in a live cell (starfish oocyte). Fluorescence recovery after photobleaching measurements were used to determine diffusion coefficients inside intracellular cross-linked structures, and it was found that the diffusion was approximately 3 to 4 orders of magnitude slower than in free solution and 2-3 orders of magnitude slower than in cytoplasm and that the value can be tuned by controlling the laser exposure. Complex structures can be fabricated to construct channels and compartments that could be used to isolate cellular processes, and the method should thus be applicable to a broad range of problems in cell biology.

Basu, Swarna; Rodionov, Vladimir; Terasaki, Mark; Campagnola, Paul J.

2005-01-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

45

Infrared multiphoton microscopy beyond 1 micron: system design and biomedical applications  

NASA Astrophysics Data System (ADS)

Here we present a multiphoton excitation microscopy setup extending the excitation wavelengths far beyond one micron. A synchronously pumped fs-OPO (OPO PP-Automatic, APE) pumped by a fs-Ti:Sapphire oscillator is used as the light source. The biological relevant wavelength range from <1050 to >1350 nm can be covered with a fixed pump frequency and a single optics set through hands free, automated tuning. Together with the Ti:Sapphire pump laser (Coherent Chameleon) excitation wavelengths from 680 to 1600nm are achieved. Two separate scanners (LaVision BioTec) are optimized for Ti:Sapphire and OPO wavelength ranges respectively including dispersion compensation for maintaining the short pulses at the sample site. An overall transmission of 30-38% up to 1400 nm was verified. Measurements on human dermis with excitation above 1 micron, compared to lower wavelengths, showed doubling of the penetration depths, strongly reduced photo damage, a 30fold increased excitation efficiency of red fluorescent dyes, including RFP and Cy5.5. Excitation at 1100 nm further leads to a 4fold decrease in autofluorescence, resulting in a significantly improved signal-to-noise ratio. The resolution is slightly reduced in comparison to Ti:Sapphire excitation, which corresponds well to the longer excitation wavelength used. Phototoxicity and photobleaching is reduced by 80- 95%. An OPO pump wavelength around 800nm opens up the possibility to use the Ti:Sapphire laser to pump the OPO and to excite the sample simultaneously giving the opportunity to excite dyes such as GFP with the pump laser and red shifted fluorophores (for instance RFP) with the OPO at the same time.

Büttner, Edlef; Andresen, Volker; Rimke, Ingo; Friedl, Peter

2007-07-01

46

Multi-photon absorption and third-order nonlinearity in silicon at mid-infrared wavelengths.  

PubMed

Silicon based nonlinear photonics has been extensively researched at telecom wavelengths in recent years. However, studies of Kerr nonlinearity in silicon at mid-infrared wavelengths still remain limited. Here, we report the wavelength dependency of third-order nonlinearity in the spectral range from 1.6 ?m to 6 ?m, as well as multi-photon absorption coefficients in the same range. The third-order nonlinear coefficient n2 was measured with a peak value of 1.65 × 10(?13) cm2/W at a wavelength of 2.1 ?m followed by the decay of nonlinear refractive index n2 up to 2.6 ?m. Our latest measurements extend the wavelength towards 6 ?m, which show a sharp decrement of n2 beyond 2.1 ?m and steadily retains above 3 ?m. In addition, the analysis of three-photon absorption and four-photon absorption processes are simultaneously performed over the wavelength range from 2.3 ?m to 4.4 ?m. Furthermore, the effect of multi-photon absorption on nonlinear figure of merit in silicon is discussed in detail. PMID:24514813

Wang, Ting; Venkatram, Nalla; Gosciniak, Jacek; Cui, Yuanjing; Qian, Guodong; Ji, Wei; Tan, Dawn T H

2013-12-30

47

Formation of Isotopically Enriched Silicon Film from Fluorosilane Produced by Isotopically Selective Infrared Multiphoton Dissociation  

NASA Astrophysics Data System (ADS)

Fabrication of isotopically enriched silicon thin film by plasma-enhanced chemical vapor deposition (PE-CVD) has been performed with source gas mixtures of SiF4, H2 and Ar. Enriched SiF4 gases with 30Si exceeding 25% were obtained from isotopically selective infrared multiphoton dissociation of hexafluorodisilane. The crystalline silicon films were successfully grown by a remote type microwave PE-CVD system on a quartz glass and Si wafers at substrate temperature of 623-1023 K. Secondary ion mass spectroscopy and energy-dispersive X-ray spectroscopy analyses indicated that the films had small impurity contents. The isotopic fraction of the grown Si film almost coincided with that of source gas.

Ohba, Hironori; Suzuki, Hiroshi; Esaka, Fumitaka; Taguchi, Tomitsugu; Yamada, Yoichi; Yamamoto, Hiroyuki; Sasase, Masato; Yokoyama, Atsushi

48

Specific local induction of DNA strand breaks by infrared multi-photon absorption  

PubMed Central

Highly confined DNA damage by femtosecond laser irradiation currently arises as a powerful tool to understand DNA repair in live cells as a function of space and time. However, the specificity with respect to damage type is limited. Here, we present an irradiation procedure based on a widely tunable Er/Yb : fiber femtosecond laser source that favors the formation of DNA strand breaks over that of UV photoproducts by more than one order of magnitude. We explain this selectivity with the different power dependence of the reactions generating strand breaks, mainly involving reactive radical intermediates, and the direct photochemical process leading to UV-photoproducts. Thus, localized multi-photon excitation with a wavelength longer than 1 µm allows for the selective production of DNA strand breaks at sub-micrometer spatial resolution in the absence of photosensitizers.

Trautlein, D.; Deibler, M.; Leitenstorfer, A.; Ferrando-May, E.

2010-01-01

49

Signal flow graph approach to multiphoton analysis and transient characteristics of mode-locked far infrared lasers  

SciTech Connect

The signal flow graph application to the analysis of multiphoton interactions has been developed in this study. It is shown that the Schroedinger equation for the multiphoton interactions can be represented as signal flow graphs in the semiclassical limit. A few examples are given to illustrate the construction, manipulation and application of the graphs. Also, the generation of temporally short far infrared pulses and their evolution in time and space have been examined experimentally and theoretically. It is shown that the far infrared pulsewidth can be as short as one-half the pump pulsewidth which is already shorter than the molecular relaxation times. In particular, the far infrared pulse energy is found to be scaled in z as e..sqrt..gz, contrary to the Beer's law growth, e/sup gz/.

Chung, H.K.

1981-01-01

50

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

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

51

Cell Adhesion on Micro-Structured Fibronectin Gradients Fabricated by Multiphoton Excited Photochemistry  

PubMed Central

Concentration gradients of ECM proteins play active roles in many areas of cell biology including wound healing and metastasis. They may also form the basis of tissue engineering scaffolds, as these can direct cell adhesion and migration and promote new matrix synthesis. To better understand cell–matrix interactions on attractive gradients, we have used multiphoton excited (MPE) photochemistry to fabricate covalently linked micro-structured gradients from fibronectin (FN). The gradient design is comprised of a parallel series of individual linear gradients with overall dimensions of approximately 800 × 800 ?m, where a linear dynamic range of nearly 10-fold in concentration was achieved. The adhesion dynamics of 3T3 fibroblasts were investigated, where the cell morphology and actin cytoskeleton became increasingly elongated and aligned with the direction of the gradient at increasing protein concentration. Moreover, the cell morphologies are distinct when adhered to regions of differing FN concentration but with similar topography. These results show that the fabrication approach allows investigating the roles of contact guidance and ECM cues on the cell–matrix interactions. We suggest this design overcomes some of the limitations with other fabrication methods, especially in terms of 3D patterning capabilities, and will serve as a new tool to study cell–matrix interactions.

Chen, Xiyi; Su, Yuan-Deng; Ajeti, Visar; Chen, Shean-Jen; Campagnola, Paul J.

2013-01-01

52

Infrared multiphoton absorption and reaction of 2-chloro-1,1,1-trifluoroethane  

SciTech Connect

The infrared multiphoton absorption and dissociation of CF/sub 3/CH/sub 2/Cl has been studied by measuring the dependence of the reaction probability and product distribution on the laser fluence and bath gas pressure. Absorption measurements were performed at two laser frequencies to establish the absorbed laser energy; the absorption measurements displayed Beer's law behavior except at very low laser fluence. Sensitized reactions with SiF/sub 4/ were conducted for comparison to the direct laser-induced process; the effective temperature within the irradiated volume for the SiF/sub 4/ experiments was determined as a function of incident laser energy. The three main reaction channels are four-centered HF elimination, three-centered HCl elimination, and C-Cl homolysis; the product ratios were very dependent on the incident laser fluence. The infrared laser-induced energy absorption and reaction processes of CF/sub 3/CH/sub 3/, CF/sub 3/CH/sub 2/Cl, and CF/sub 3/CH/sub 2/Br are compared. The data provide evidence for a fluence-dependent fractionation of absorbed laser energy producing a two-component energy distribution for the former two compounds. 24 references, 10 figures, 2 tables.

Setser, D.W.; Lee, T.S.; Danen, W.C.

1985-12-19

53

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

54

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

55

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

PubMed

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

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

2013-02-14

56

Multiphoton spectroscopy of human skin in vivo  

NASA Astrophysics Data System (ADS)

In vivo multiphoton-intensity images and emission spectra of human skin are reported. Optical sections from different depths of the epidermis and dermis have been measured with near-infrared laser-pulse excitation. While the intensity images reveal information on the morphology, the spectra show emission characteristics of main endogenous skin fluorophores like keratin, NAD(P)H, melanin, elastin and collagen as well as of second harmonic generation induced by the excitation-light interaction with the dermal collagen network.

Breunig, Hans G.; Weinigel, Martin; König, Karsten

2012-02-01

57

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).

LIU, LIXIN; SHAO, YONGHONG; NIU, HANBEN

2013-01-01

58

Discussion of the role of many-electron motions in multiphoton ionization and excitation.  

National Technical Information Service (NTIS)

The character of many-electron interactions in atoms is examined in relation to a possible role for these couplings in multiphoton processes. It is found that they provide a natural mechanism which can produce both (1) anomalously rapid rates of multiphot...

K. Boyer H. Jara T. S. Luk I. A. McIntyre A. McPherson

1987-01-01

59

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

Microsoft Academic Search

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

Elba E. Serrano; V. B. Knight

2005-01-01

60

Infrared Multiphoton Dissociation of Small-Interfering RNA Anions and Cations  

PubMed Central

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 to 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 ~25 – 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.

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

2010-01-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

62

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

PubMed

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

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

2012-11-01

63

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

64

Lung alveolar wall disruption in three-dimensional space identified using second-harmonic generation and multiphoton excitation fluorescence  

NASA Astrophysics Data System (ADS)

Second harmonic generation and multiphoton excited fluorescence microscopy methods were used to examine structural remodeling of the extracellular matrix in human lung alveolar walls undergoing emphysematous destruction. Fresh lung samples removed from a patient undergoing lung transplantation for very severe chronic obstructive pulmonary disease were compared to similar samples from an unused donor lung that served as a control. The generated spatially resolved 3D images show the spatial distribution of collagen, elastin and other endogenously fluorescent tissue components such as macrophages. In the case of control lung tissue, we found well ordered alveolar walls with composite type structure made up of collagen matrix and relatively fine elastic fibers. In contrast, lung tissue undergoing emphysematous destruction was highly disorganized with increased alveolar wall thickness compared to control lung tissue.

Abraham, Thomas; Hogg, James

2010-02-01

65

Circular dichroism and photoelectron angular distributions of excited states of cesium and rubidium using resonantly enhanced multiphoton ionization techniques  

SciTech Connect

Resonantly enhanced multiphoton ionization (REMPI) techniques are used to study spin-orbit effects in the photoelectron angular distributions (PEAD) of excited ns (n = 8-13) states of cesium. The asymmetry parameters are shown to exhibit an energy dependence in the region of the Cooper minimum of the photoionization cross section, supporting predictions made by inclusion of relativistic coupling in the continuum. REMPI is also used to study the photoelectron angular distribution of excited n[sup 2]P[sub 3/2] and n[sup 2]P[sub 1/2] state of cesium and rubidium. The measured asymmetry parameters for the PEADs of n[sup 2]P[sub 3/2] states are found to deviate signi ficantly from theoretical predictions. The difference is attributed to depolarization of the angular momentum polarization due to hyperfine coupling. Circular dichroism effects in the photoelectron angular distributions (CDAD) are used to measure alignment of the excited n[sup 2]P[sub 3/2] states of cesium and rubidium. Angular distributions of the n[sup 2]P[sub 1/2] states are used to show that isotropic states do not exhibit CDAD.

Cuellar, L.E.

1993-01-01

66

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

PubMed Central

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

Gualda, Emilio J.; Vazquez de Aldana, Javier R.; Martinez-Garcia, M. Carmen; Moreno, Pablo; Hernandez-Toro, Juan; Roso, Luis; Artal, Pablo; Bueno, Juan M.

2011-01-01

67

Resonance enhanced multiphoton ionization spectroscopy of the NCl molecule: 1Sigma Rydberg states studied by 2-photon excitation from the a1Delta state  

NASA Astrophysics Data System (ADS)

Three 1sigma Rydberg states of the NCl molecule, accessed from the NCl a1 state, have been investigated by multiphoton ionization spectroscopy. NCl was prepared from the Cl + N3 reaction and the excited 1sigma states were observed via the 2-photon resonance enhancements they provide in the multiphoton ionization spectrum of NCl a1 . Assignment of the initial and final electronic states associated with each band was achieved by rotational band contour simulations, least-squares fitting of the resolved rotational structure, recording spectra with linearly and circularly polarized radiation and recording spectra in the N35Cl+ and N37Cl+ mass channels. The +/- character of each excited state as well as the dominant electronic configuration at spectroscopically accessible bond lengths was established by multireference double excitation configuration interaction (MRDCI) calculations.

Boggis, S. A.; Dyke, J. M.; Tabrizchi, M.; Richter, R.

1999-07-01

68

Current developments in clinical multiphoton tomography  

NASA Astrophysics Data System (ADS)

Two-photon microscopy has been introduced in 1990 [1]. 13 years later, CE-marked clinical multiphoton systems for 3D imaging of human skin with subcellular resolution have been launched by the JenLab company with the tomograph DermaInspectTM. In 2010, the second generation of clinical multiphoton tomographs was introduced. The novel mobile multiphoton tomograph MPTflexTM, equipped with a flexible articulated optical arm, provides an increased flexibility and accessibility especially for clinical and cosmetical examinations. The multiphoton excitation of fluorescent biomolecules like NAD(P)H, flavins, porphyrins, elastin, and melanin as well as the second harmonic generation of collagen is induced by picojoule femtosecond laser pulses from an tunable turn-key near infrared laser system. The ability for rapid highquality image acquisition, the user-friendly operation of the system, and the compact and flexible design qualifies this system to be used for melanoma detection, diagnostics of dermatological disorders, cosmetic research, and skin aging measurements as well as in situ drug monitoring and animal research. So far, more than 1,000 patients and volunteers have been investigated with the multiphoton tomographs in Europe, Asia, and Australia.

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

2010-02-01

69

Increased Sequence Coverage of Thymine-rich Oligodeoxynucleotides by Infrared Multiphoton Dissociation Compared to Collision Induced Dissociation  

PubMed Central

Infrared multiphoton dissociation (IRMPD) of thymine-rich oligodeoxynucleotides in a linear ion trap mass spectrometer affords far more extensive fragmentation than conventional collision induced dissociation (CID). For oligodeoxynucleotides containing one non-thymine base, CID results primarily in cleavage on the 3? side of the non-thymine nucleobase, whereas IRMPD results in cleavages between all of the nucleobases and thus provides complete sequence coverage. Furthermore, for oligodeoxynucleotides containing a single non-thymine base, it is shown that the full series of diagnostic sequence ions observed in the IRMPD mass spectra arise from secondary dissociation of the two primary products formed from the initial cleavage site located next to the non-thymine base.

Parr, Carol; Brodbelt, Jennifer S.

2011-01-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

71

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

SciTech Connect

Multi-photon ionization (MPI) of the RNA base uracil has been studied in the wavelength range 220–270 nm, coinciding with excitation to the S{sub 2}(??*) state. A fragment ion at m/z = 84 was produced by 2-photon absorption at wavelengths ?232 nm and assigned to C{sub 3}H{sub 4}N{sub 2}O{sup +} 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 C{sub 3}H{sub 3}NO{sup +}) but represses C{sub 3}H{sub 4}N{sub 2}O{sup +} 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. [Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)] [Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

2013-12-28

72

Studies in Infrared Multiple Photon Excitations.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. Infrared Multiple Photon Excitation and Dissociation (IRMPE/D) have been investigated, using shaped CO _2 laser pulses with uniform intensity/time profiles and Gaussian spatial profiles, allowing fluence (Jcm^{-2}) and intensity (Wcm^{-2}) to be varied independently, and a full deconvolution of quantities measured as spatial averages. Extensive absorption measurements on SF _6 and CF_3I, performed optoacoustically but calibrated absolutely, have quantified the separate fluence and intensity effects on absorption cross-sections. The results on SF_6 should now constitute the most extensive data base for this molecule, and have been compared with a simulation of IRMPE performed using Quack's statistical mechanical equations for IR pumping. An excellent agreement of experimental and simulated data is obtained. Experiments on the smaller NH_3 molecule have demonstrated the importance of collisional pressure broadening in allowing IRMPE to occur. A value for the NH_3-NH_3 self-broadening parameter at 10P30 (934.9 cm ^{-1}) has been measured, at 20 MHzTorr^{-1}. IRMPD of CF_3I has been followed in real time, using Resonance Enhanced Multiple Photon Ionisation (REMPI) detection of iodine atoms, both during and after shaped pulses of well defined duration. The dependence of dissociation yield on intensity has been quantified, and an estimate made for the high intensity limiting IR rate constant, k = 1.6 times 10^6 s^{ -1}/MWcm^{-2}. The slow unimolecular decay of threshold CF_3 I molecules after the CO_2 pulse has been studied by monitoring the excited state iodine atom REMPI signal. Threshold decay rates of (6 -7) times 10^5 s^{-1} have been measured, which compare well with values from previous SACT calculations on CF_3I. Shaped pulse measurements on the IRMPD of CF _3CN, with Laser Induced Fluorescence (LIF) detection of CN, have quantified the dependence on CO _2 laser intensity of CN rotational and vibrational temperatures, previously only measured qualitatively.

Sutton, Paul David

73

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

74

Multiphoton photoluminescence from GaN with tunable picosecond pulses  

SciTech Connect

UV photoluminescence (PL) from GaN thin films was observed by multiphoton excitation. The two-photon PL excitation spectrum near the band gap agrees with the theoretical two-photon-absorption spectrum. The pump-intensity dependence and the PL excitation spectrum in the infrared indicate the existence of midgap defect states around 1 eV above the valence band. This is confirmed by the PL excitation spectrum obtained with a two-color, two-photon excitation process. {copyright} {ital 1997} {ital The American Physical Society}

Kim, D.; Libon, I.H.; Voelkmann, C.; Shen, Y.R.; Petrova-Koch, V. [Department of Physics, University of California, Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720-7300 (United States)] [Department of Physics, University of California, Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720-7300 (United States)

1997-02-01

75

Multiphoton Processes.  

National Technical Information Service (NTIS)

The main features of multiphoton processes are described on a somewhat elementary basis. The emphasis is put on multiphoton ionization of atoms where the influence of resonance effects is given through typical examples. The important role played by the co...

C. Manus G. Mainfray

1980-01-01

76

Infrared multiphoton dissociation of the siderophore enterobactin and its Fe(III) complex. Influence of Fe(III) binding on dissociation kinetics and relative energetics  

Microsoft Academic Search

The dissociation pathways of the siderophore enterobactin and its complex with Fe(III) were examined using infrared multiphoton\\u000a dissociation (IRMPD). Under experimental conditions (pH = 3.5), both compounds’ electrospray spectra exhibited exclusively\\u000a singly-charged anions. The compositions of the dissociation products were characterized by accurate mass measurements using\\u000a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The primary dissociation channel for

Andrew D. Leslie; Rambod Daneshfar; Dietrich A. Volmer

2007-01-01

77

Multifocal multiphoton microscopy.  

PubMed

We present a real-time, direct-view multiphoton excitation fluorescence microscope that provides three-dimensional imaging at high resolution. Using a rotating microlens disk, we split the near-infrared light of a mode-locked titanium-sapphire laser into an array of beams that are transformed into an array of high-aperture foci at the object. We typically scan at 225 frames per second and image the fluorescence with a camera that reads out the images at video rate. For 1.4 aperture oil and 1.2 water immersion lenses at 780-nm excitation we obtained axial resolutions of 0.84 and 1.4mum , respectively, which are similar to that of a single-beam two-photon microscope. Compared with the latter setup, our system represents a 40-100-fold increase in efficiency, or imaging speed. Moreover, it permits the observation with the eye of high-resolution two-photon images of (live) samples. PMID:18087301

Bewersdorf, J; Pick, R; Hell, S W

1998-01-01

78

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

79

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

PubMed

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

Xu, Zhe; Brodbelt, Jennifer S

2014-01-01

80

Multiphoton interactions in the strong field regime: Microwave excitation and ionization of Rydberg eigenstates  

NASA Astrophysics Data System (ADS)

We present here an experimental study and theoretical exposition of two-level atoms in the strong field regime, i.e. a regime where we must resort to quantum mechanical techniques other than perturbation theory to properly describe the interactions that take place, as well as an experimental investigation of the many-level problem of microwave ionization. All involve the interaction of Rydberg atoms, atoms with one highly excited electron, with short pulses of radio-frequency or microwave radiation. We also show the relationship between the single cycle time propagator (SCTP), which is simply a time integral of the Schrodinger equation over one cycle of a periodic field, and Floquet theory. We then go on to apply the SCTP to calculate Rabi frequencies, show the dramatic effect of phase in a pulse, and describe the effects of frequency modulation of a strong field.

Griffith, Warren Morton

81

Infrared light excites cells by changing their electrical capacitance.  

PubMed

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

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

2012-01-01

82

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

NASA Astrophysics Data System (ADS)

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

Kalli, Anastasia; Hess, Sonja

2012-02-01

83

Infrared imaging results of an excited planar jet  

SciTech Connect

Planar jets are used for many applications including heating, cooling, and ventilation. Generally such a jet is designed to provide good mixing within an enclosure. In building applications, the jet provides both thermal comfort and adequate indoor air quality. Increased mixing rates may lead to lower short-circuiting of conditioned air, elimination of dead zones within the occupied zone, reduced energy costs, increased occupant comfort, and higher indoor air quality. This paper discusses using an infrared imaging system to show the effect of excitation of a jet on the spread angle and on the jet mixing efficiency. Infrared imaging captures a large number of data points in real time (over 50,000 data points per image) providing significant advantages over single-point measurements. We used a screen mesh with a time constant of approximately 0.3 seconds as a target for the infrared camera to detect temperature variations in the jet. The infrared images show increased jet spread due to excitation of the jet. Digital data reduction and analysis show change in jet isotherms and quantify the increased mixing caused by excitation. 17 refs., 20 figs.

Farrington, R.B.

1991-12-01

84

Detecting cracks in teeth using ultrasonic excitation and infrared imaging  

NASA Astrophysics Data System (ADS)

We describe a new technique, Thermosonics, that can be used to detect cracks in teeth. This technique was initially invented and developed for finding cracks in industrial and aerospace applications. The thermosonics technique employs a single short pulse (typically tens of milliseconds) of ultrasound excitation combined with infrared imaging. Ultrasonic waves vibrate the target material. This vibration causes rubbing and clapping between faying surfaces of any cracks which are present, resulting in a temperature rise around the cracks. An infrared camera is used to image the temperature distribution during and after the ultrasound excitation. Thus, cracks in teeth can be detected. Although this technique is still under development, it shows promise for clinical use by dentists.

Han, Xiaoyan; Favro, Lawrence D.; Thomas, Robert L.

2001-06-01

85

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

86

Preparation of polarized molecules using coherent infrared multicolor ladder excitation.  

PubMed

A density matrix treatment is presented for a general process of preparing polarized molecules through their coherent interaction with two or more infrared photons of different frequencies, each tuned to cause a transition between real levels. This process, which might be called infrared stimulated Raman adiabatic passage, allows complete population transfer to selected rotational-vibrational levels and controls the direction of the rotational angular momentum vector J of the molecule with the possibility of preparing higher moments of the J spatial distribution. HCl molecules in a supersonic molecular beam are considered as a candidate system. Theory predicts that under collision-free conditions two infrared laser pulses of microsecond duration and milliwatt power are able to achieve complete population transfer and alignment of HCl (v=2, J=2, and M=0) for mutually parallel excitation and HCl (v=2, J=2, and M=+/-1) for mutually perpendicular excitation. Orientation of the HCl (v=2, J=2, and M=+/-2) can also be achieved using two circularly polarized pulses of the same helicity. For simplicity, our treatment ignores nuclear spin depolarization, which would be the case for molecules such as (12)C(16)O and (12)C(16)OO(2). Polarized molecules in higher vibrational levels can be prepared using additional infrared pulses. PMID:20423176

Mukherjee, Nandini; Zare, Richard N

2010-04-21

87

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

88

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

SciTech Connect

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.

Goto, M.; Hansen, K. [Department of Physics, University of Gothenburg, 41296 Gothenburg (Sweden)

2011-12-07

89

Controlling condensed-phase vibrational excitation with tailored infrared pulses  

NASA Astrophysics Data System (ADS)

Vibrational population distributions within the CO-stretching T 1u manifold of W(CO) 6 in room-temperature n-hexane were created by using near-transform limited and linearly chirped picosecond infrared excitation pulses. These pulses were characterized using the second harmonic FROG (frequency-resolved optical gating) algorithm to determine the ˜8 cm -1/ps chirp for both positively- and negatively-chirped 2 ps pulses. FROG and time-resolved transient difference spectra were obtained with an InSb focal plane array detector. While unchirped and positively-chirped excitation leads predominantly to v=1 population, negatively-chirped pulses produce excess population in the v=2 level. These results are compared to predictions from density matrix calculations for a model potential.

Kleiman, V. D.; Arrivo, S. M.; Melinger, J. S.; Heilweil, E. J.

1998-08-01

90

MULTIVARIATE ANALYSIS OF ELECTRON DETACHMENT DISSOCIATION AND INFRARED MULTIPHOTON DISSOCIATION MASS SPECTRA OF HEPARAN SULFATE TETRASACCHARIDES DIFFERING ONLY IN HEXURONIC ACID STEREOCHEMISTRY  

PubMed Central

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

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

2011-01-01

91

Pressure and power dependence in the infrared laser photolysis of 1-chloro-1-fluoroethylene: experiment and modeling calculations  

SciTech Connect

Dissociation of 1-chloro-1-fluoroethylene following infrared multiphoton excitation was monitored via infrared fluorescence of the products, either HCl* or HF*. Total dissociation yield and branching ratio were monitored as functions of, respectively, pressure and photolytic intensity. A rate equations model of the excitation and dissociation process is shown to be consistent with both sets of data.

Nogar, N.S.; Jalenak, W.A.

1981-01-01

92

Theory of high intensity, multiphoton processes in Alkali metal atoms  

NASA Astrophysics Data System (ADS)

Strong field multiphoton processes take place when a system whose binding energy is several times the photon energy interacts with an intense, ultrafast laser pulse. Until recently, most of the available high power lasers provided radiation in the visible/near-infrared region, meaning that most studies of multiphoton physics have been performed on rather tightly bound systems such as the rare gases. The advent of a new class of laser systems, capable of producing intense radiation in the mid-infrared (mid-IR) regime (wavelengths between 3 and 4 ?m) opens the possibilitiy of observing multiphoton processes in a new group of systems with lower ionization potentials than those previously studied. Of particular interest are the Alkali metal atoms which are true one-(valence)-electron systems, with a strong ground-to-first excited state coupling. We present theoretical calculations of above threshold ionization and high harmonic generation from alkali metal atoms subject to 0.3-0.4 eV laser irradiation and compare them to recent experiments. We discuss a number of striking differences between these atoms and the well-known results for rare gases.

Schafer, Kenneth J.

1999-11-01

93

Effective novel dissociation methods for intact protein: Heat-assisted nozzle-skimmer collisionally induced dissociation and infrared multiphoton dissociation using a Fourier transform ion cyclotron resonance mass spectrometer equipped with a micrometal electrospray ionization emitter  

Microsoft Academic Search

Heating of a nano-electrospray ionization (nanoESI) source can improve the dissociation efficiency of collisionally induced dissociation (CID) methods, such as nozzle-skimmer CID (NS–CID) and infrared multiphoton dissociation (IRMPD), for large biomolecule fragmentation. A metal nanoESI emitter was used due to its resistance to heating above 250°C. This novel method for the dissociation of large biomolecular ions is termed “heat-assisted NS–CID”

Naoyuki Yamada; Ei-ichiro Suzuki; Kazuo Hirayama

2006-01-01

94

Quantum dot infrared photodetector enhanced by surface plasma wave excitation.  

PubMed

Up to a thirty-fold detectivity enhancement is achieved for an InAs quantum dot infrared photodetector (QDIP) by the excitation of surface plasma waves (SPWs) using a metal photonic crystal (MPC) integrated on top of the detector absorption region. The MPC is a 100 nm-thick gold film perforated with a 3.6 microm period square array of circular holes. A bare QDIP shows a bias-tunable broadband response from approximately 6 to 10 microm associated with the quantum confined Stark (QCS) effect. On the other hand, an MPC-integrated QDIP exhibits a dominant peak at 11.3 microm with a approximately 1 microm full width at half maximum and the highly enhanced detectivity at the bias polarity optimized for long wavelength. This is very different from the photoresponse of the bare QDIP but fully consistent with the direct coupling of the QDs in the detector absorption region to the SPWs excited at the MPC/detector interface by incident photons. The SPW resonance wavelength, lambda, for the smallest coupling wavevector of the array in the MPC is close to 11.3 microm. The response also shows other SPW-coupled peaks: a significant peak at 8.1 microm (approximately lambda/radical2) and noticeable peaks at 5.8 microm (approximately lambda/2) and 5.4 microm (approximately lambda/ radical5) which correspond to higher-order coupling wavevectors. For the opposite bias, the MPC-integrated QDIP shows the highest response at 8.1 microm, providing a dramatic voltage tunability that is associated with QCS effect. SPWs propagate with TM (x, z) polarization along the MPC/detector interface. The enhanced detectivity is explained by these characteristics which increase both the effective absorption cross section with propagation and the interaction strength with TM polarization in the coupling to the QDs. Simulations show good qualitative agreement with the observed spectral behavior. PMID:20052244

Lee, S C; Krishna, S; Brueck, S R J

2009-12-01

95

Control of multiphoton and avalanche ionization using an ultraviolet-infrared pulse train in femtosecond laser micro/nano-machining of fused silica  

NASA Astrophysics Data System (ADS)

We report on the experimental results of micro- and nanostructures fabricated on the surface of fused silica by a train of two femtosecond laser pulses, a tightly focused 266 nm (ultraviolet, UV) pulse followed by a loosely focused 800 nm (infrared, IR) pulse. By controlling the fluence of each pulse below the damage threshold, micro- and nanostructures are fabricated using the combined beams. The resulting damage size is defined by the UV pulse, and a reduction of UV damage threshold is observed when the two pulses are within ~ 1 ps delay. The effects of IR pulse duration on the UV damage threshold and shapes are investigated. These results suggest that the UV pulse generates seed electrons through multiphoton absorption and the IR pulse utilizes these electrons to cause damage by avalanche process. A single rate equation model based on electron density can be used to explain these results. It is further demonstrated that structures with dimensions of 124 nm can be fabricated on the surface of fused silica using 0.5 NA objective. This provides a possible route to XUV (or even shorter wavelength) laser nano-machining with reduced damage threshold.

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

2014-03-01

96

Multiphoton dissociation of SF6 by a molecular beam method  

NASA Astrophysics Data System (ADS)

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 SF6, the pulse duration of the CO2 laser, and the frequency in both one and two laser experiments. Translational energy distributions of the primary dissociation product SF5, measured by time-of-flight and angular distributions and the dissociation lifetime of excited SF6 as inferred from the observation of secondary dissociation of SF5 into SF4 and F during the laser pulse suggest that the dynamics of dissociation of excited molecules is dominated by complete energy randomization and rapid intramolecular energy transfer and can be adequately described by RRKM theory. An improved phenomenological model including the initial intensity dependent excitation, a rate equation describing the absorption and stimulated emission of single photons, and the unimolecular dissociation of excited molecules is constructed based on available experimental results. Our studies show that although the energy fluence of the laser determines the dissociation yield of molecules in the quasicontinuum, the role played by the intensity of the laser in multiphoton dissociation is more significant than just that of overcoming the intensity dependent absorption in the lowest levels. Once molecules are excited beyond the dissociation energy, the average level of excitation of the dissociating molecules will be significantly influenced by the laser intensity for a given energy fluence when the rate of decomposition starts to compete with the rate of up-excitation.

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

1980-05-01

97

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

PubMed

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

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

2012-03-15

98

Optical biopsy of liver fibrosis by use of multiphoton microscopy  

NASA Astrophysics Data System (ADS)

We demonstrate the application of multiphoton microscopy in diagnosing toxin- CCl4 - induced liver fibrosis in mice. Although hepatocyte autofluorescence does not vary significantly, different degrees of necrosis and stellate cell proliferation at necrotic sites in livers with fibrosis (ex vivo) can be detected easily from multiphoton-induced autofluorescence images by use of 780-nm excitation. Our result suggests that multiphoton microscopy can be developed into an effective technique for the detection and diagnosis of liver fibrosis in vivo.

Lee, Hsuan-Shu; Liu, Yuan; Chen, Hsiao-Ching; Chiou, Ling-Ling; Huang, Guan-Tarn; Lo, Wen; Dong, Chen-Yuan

2004-11-01

99

Infrared emission from photo-excited gaseous benzene: detection with a new home-made spectrometer  

NASA Astrophysics Data System (ADS)

The infrared fluorescence decay and the dispersed emission spectrum are presented for gaseous benzene following 193 nm laser excitation. They were measured with FIREFLY (Fluorescence in the InfraRed from Excited FLYing molecules), a new home-made spectrometer. Redshift and redtail in the CH stretch emission spectra (3.3 ?m region) demonstrate that anharmonicity plays a key role when dealing with high internal energies, as it is the case in the interstellar medium.

Féraud, G.; Carpentier, Y.; Pino, T.; Longval, Y.; Dartois, E.; Chamaillé, T.; Vasquez, R.; Vincent, J.; Parneix, P.; Falvo, C.; Bréchignac, Ph.

2012-02-01

100

Infrared video microscopy for visualizing neurons and neuronal excitation in brain slices.  

PubMed

Here we describe methods for imaging neurons and neuronal excitation in brain slices with infrared video microscopy. Patch clamping in conjunction with a gradient-contrast system allows electrical recording from fine neuronal processes. Imaging with an infrared (IR)-darkfield system allows visualization of the intrinsic optical signal (IOS). PMID:24298032

Dodt, Hans-Ulrich; Becker, Klaus; Zieglgänsberger, Walter

2013-12-01

101

High-resolution spectroscopy and dynamics of multiphoton processes in atoms and molecules  

Microsoft Academic Search

This report summarizes research on resonantly enhanced multiphoton absorption dissociation, and ionization processes in atoms and molecules. Multiphoton processes are studied using from one to three independently tunable visible and\\/or UV laser beams in order to establish both the underlying physics and the high degree of selectivity of multiphoton processes. Measurements are made to probe both the formation of excited

P. M. Dehmer; J. L. Dehmer

1985-01-01

102

Infrared multiphoton dissociation spectroscopy of cationized serine: effects of alkali-metal cation size on gas-phase conformation.  

PubMed

The gas-phase structures of alkali-metal cation complexes of serine (Ser) are examined using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. Spectra of Li+(Ser) and Na+(Ser) are similar and relatively simple, whereas Cs+(Ser) includes distinctive new IR bands, and K+(Ser) and Rb+(Ser) exhibit intermediate behavior. Measured IRMPD spectra are compared to spectra calculated at a B3LYP/6-311+G(d,p) level to identify the structures present in the experimental studies. On the basis of these experiments and calculations, the only conformations accessed for the complexes to the smaller alkali-metal cations, Li+ and Na+, are charge-solvated structures involving tridentate coordination to the amine and carbonyl groups of the amino acid backbone and to the hydroxyl group of the side chain, M1[N,CO,OH]. For the cesiated complex, a band corresponding to a zwitterionic structure, ZW[CO2-], is clearly visible. K+(Ser) and Rb+(Ser) exhibit evidence of the charge-solvated analogue of the zwitterions, M3[COOH], in which the metal cation binds to the carboxylic acid group. Calculations indicate that the relative stability of the M3[COOH] structure is very strongly dependent on the size of the metal cation, consistent with the range of conformations observed experimentally. PMID:18288825

Armentrout, P B; Rodgers, M T; Oomens, J; Steill, J D

2008-03-20

103

Infrared multiphoton dissociation spectroscopy of cationized threonine: effects of alkali-metal cation size on gas-phase conformation.  

PubMed

The gas-phase structures of alkali-metal cation complexes of threonine (Thr) are examined using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser in conjunction with quantum chemical calculations. Spectra of Li+(Thr) and Na+(Thr) are similar and relatively simple, whereas K+(Thr), Rb+(Thr), and Cs+(Thr) include distinctive new IR bands. Measured IRMPD spectra are compared to spectra calculated at a B3LYP/6-311+G(d,p) level to identify the structures present in the experimental studies. For the smaller metal cations, the spectra match those predicted for charge-solvated structures in which the ligand exhibits tridentate coordination, M1[N,CO,OH], binding to the amide and carbonyl groups of the amino acid backbone and to the hydroxyl group of the side chain. K+(Thr), Rb+(Thr), and Cs+(Thr) exhibit evidence of the charge-solvated complex, M3[COOH], in which the metal cation binds to the carboxylic acid group. Evidence for a small population of the zwitterionic analogue of this structure, ZW[CO2-], is also present, particularly for the Cs+ complex. Calculations indicate that the relative stability of the M3[COOH] structure is very strongly dependent on the size of the metal cation, consistent with the range of conformations observed experimentally. The present results are similar to those obtained previously for the analogous M+(Ser) complexes, although there are subtle distinctions that are discussed. PMID:18288826

Rodgers, M T; Armentrout, P B; Oomens, J; Steill, J D

2008-03-20

104

Three-dimensional multiphoton autofluorescence spectral imaging of live tissues  

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

105

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

106

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

107

Stepwise multi-photon activation fluorescence reveals a new method of melanoma imaging for dermatologists  

NASA Astrophysics Data System (ADS)

Previous research has shown that the stepwise multi-photon activated fluorescence (SMPAF) of melanin, activated by a continuous-wave (CW) mode near infrared (NIR) laser, is a low cost and reliable method of detecting melanin. SMPAF images of melanin in a mouse hair and a formalin fixed mouse melanoma were compared with conventional multiphoton fluorescence microscopy (MPFM) images and confocal reflectance microscopy (CRM) images, all of which were acquired at an excitation wavelength of 920 nm, to further prove the effectiveness of SMPAF in detecting melanin. SMPAF images add specificity for melanin detection to MPFM images and CRM images. Melanin SMPAF can be a promising technology to enable melanoma imaging for dermatologists.

Lai, Zhenhua; Lian, Christine; Ma, Jie; Yu, Jingyi; Gu, Zetong; Rajadhyaksha, Milind; DiMarzio, Charles A.

2014-02-01

108

Multiphoton Detection Techniques for F and F2.  

National Technical Information Service (NTIS)

This report describes research toward the development of quantitative remote diagnostics for atomic and molecular fluorine, using ultraviolet multiphoton excitation followed by the detection of fluorescence or ionization. The first demonstration of resona...

D. L. Huestis G. W. Faris M. J. Dyer W. K. Bischel

1990-01-01

109

Ab initio study of the orientation effects in multiphoton ionization and high-order harmonic generation from the ground and excited electronic states of H{sub 2}{sup +}  

SciTech Connect

We present an ab initio three-dimensional (3D) calculation of multiphoton ionization (MPI) and high-order harmonic generation (HHG) of the hydrogen molecular ions subject to intense linearly polarized laser pulses. The orientation of the molecular axis with respect to the polarization of the laser field can be arbitrary. The numerical procedure involves the extension of the generalized pseudospectral (GPS) method for nonuniform spatial discretization of the Hamiltonian and wave functions and time propagation using the split-operator technique in the energy representation. The calculations were performed for the ground and two first excited electronic states of H{sub 2}{sup +} at the internuclear separation R=2.0 a.u. The laser pulse has a sine-squared envelope and contains 20 optical cycles with the wavelength 800 nm. The dependence of MPI and HHG on the orientation angle is analyzed. We show that orientation effects are strongly affected by the symmetry of the wave function and the corresponding distribution of the electron density. While the anisotropy of MPI and HHG is rather weak for the 1{sigma}{sub g} state, both processes are suppressed at the orientation angle 90 deg. for the 1{sigma}{sub u} state and at the angle 0 deg. for the 1{pi}{sub u} state. We discuss the multiphoton resonance and two-center interference effects in the HHG spectra which can lead both to enhancement and suppression of the harmonic generation.

Telnov, Dmitry A.; Chu, Shih-I [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States)

2007-10-15

110

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

111

Excitation mechanism of blue and infrared emission in ZnSe:Cr  

Microsoft Academic Search

ZnSe:Cr-based infrared (IR) laser operating at room temperature is of great interest shows the near-edge photoluminescence (PL) spectra of Cr-doped ZnSe observed under 337.1 nm excitation. A broad blue PL band at 427 nm is observed for lightly Cr-doped samples and the sample doped with Cr from the Bi + Cr melt. Blue PL band is excited by two-step complementary

V. P. Sirkeli; O. V. Kulikova; L. L. Kulyuk; R. Laiho; E. Lahderanta; D. D. Nedeoglo; N. D. Nedeoglo; A. V. Siminel; R. L. Sobolevskaya; K. D. Sushkevich

2007-01-01

112

Multiphoton microscopy of atheroslcerotic plaques  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is a techniques that fascilitates three dimensional imaging of intact, unstained tissue. Especially connective tissue has a relatively strong nonlinear optical response and can easily be imaged. Atherosclerosis is a disease where lipids accumulate in the vessel wall and there is a thickening of the intima by growth of a cap of connective tissue. The mechanical strength of this fibrous cap is of clinically importance. If the cap ruptures a thrombosis forms which can block a coronary vessel and therby causing myocardial infarction. Multiphoton microscopy can be used to image the fibrous cap and thereby determine the thickness of the cap and the structure of the connective fibres. This could possibly be developed into a diagnostic and clincal tool to monitor the vulnerability of a plaque and also to better understand the development of a plaque and effects of treatment. We have collected multiphoton microscopy images from atherosclerotic plaque in human aorta, both two photon excited fluorescens and second harmonic generated signal. The feasability of using this technique to determine the state of the plaque is explored.

Lilledahl, Magnus B.; de Lange Davies, Catharina; Haugen, Olav A.; Svaasand, Lars O.

2007-03-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

114

In vivo stepwise multi-photon activation fluorescence imaging of melanin in human skin  

NASA Astrophysics Data System (ADS)

The stepwise multi-photon activated fluorescence (SMPAF) of melanin is a low cost and reliable method of detecting melanin because the activation and excitation can be a continuous-wave (CW) mode near infrared (NIR) laser. Our previous work has demonstrated the melanin SMPAF images in sepia melanin, mouse hair, and mouse skin. In this study, we show the feasibility of using SMPAF to detect melanin in vivo. in vivo melanin SMPAF images of normal skin and benign nevus are demonstrated. SMPAF images add specificity for melanin detection than MPFM images and CRM images. Melanin SMPAF is a promising technology to enable early detection of melanoma for dermatologists.

Lai, Zhenhua; Gu, Zetong; Abbas, Saleh; Lowe, Jared; Sierra, Heidy; Rajadhyaksha, Milind; DiMarzio, Charles

2014-03-01

115

The effects of infrared radiation on trapped electrons in excited ZnS-phosphors  

Microsoft Academic Search

By means of rise curves the number of traped electrons in ZnS-phosphors can be determined. The effect of infrared irradiation added simultaneously to UV excitation is that of quenching; in addition the number of occupied traps (nt) is found to be considerably reduced; approximately in the same ratio as the reduction of light. Since the free electron concentration (n) is

B. Kramer; M. Schön

1960-01-01

116

Multiphoton quantum communication in quantum networks  

NASA Astrophysics Data System (ADS)

We propose and analyze a multiphoton-state coherent transport protocol in a coupled-resonator quantum network. A multiphoton swap gate between two antipodes can be achieved with neither external modulation nor coupling strength engineering. Moreover, we extend this result to a coupled-resonator chain of arbitrary length with different coupling strengths. Effects of decoherence via quantum nondemolition interaction are studied with sources including vacuum quantum fluctuation and bath thermal excitations when the bath is in the thermal equilibrium state. These observations are helpful to understand the decoherence effects on quantum communication in quantum coupled-resonator systems.

Qin, Wei; Wang, Chuan; Cao, Ye; Long, Gui Lu

2014-06-01

117

An investigation into the physics of the infrared excited luminescence of irradiated feldspars  

NASA Astrophysics Data System (ADS)

Infrared excitation of irradiated feldspars produces a luminescence glow in one or more broad emission bands. The processes are poorly understood, but they are suspected to occur in lattice defects, although their general identity is unknown. This thesis is about trying to understand more about the physics of these processes. I found the emission intensity increased as the temperature was increased above 20°C for emission bands with peak intensities at wavelengths around 330, 400 and 570 nm, but the rate of increase dropped off for some samples as the temperature was increased over 80°C. These results were interpreted as being due to the excitation of different vibrational modes of the feldspar structure. The rate of decay in the emission intensity of one sample was independent of temperature. The latter was clear evidence against a model where charge is excited from a trap by a combination of both optical and thermal excitation. The emission intensities of some emission bands were dependent on the polarization of the infrared exciting light, and the emission itself was polarized in some cases. These results were explained by dipolar transitions occurring within unknown defect centres located at either the T1, M or OD lattice sites. This explanation was supported by studies on transitions within Fe+3 ions occupying known lattice sites. I also found that there was a small photoconductivity with green light excitation, but no measurable effect with infrared excitation. However I could not rule out the possibility that charge was excited to delocalized bands in both cases. A model is proposed to explain these results with one basic type of electron trap which is excited by the infrared light. The excited electron can either tunnel through to a recombination centre or it can be thermally excited to the conduction band or to a state just below the conduction band. Anion defects are shown to be possible centres for the traps. Changes in the fraction of electrons that tunnel to the recombination centres, and electron spin interactions are proposed as additional mechanisms that may also have some effect on the changes in emission intensity with temperature.

Short, Michael Anthony

118

[Application of nanophosphors with near infrared excitation for biomedical imaging].  

PubMed

Fluorescence bioimaging is an inevitable method for biological, medical and pharmaceutical sciences to visualize substances in biological objects in a highly sensitive, multicolor and dynamic way. Recently, elongation of the fluorescence wavelength is a trend used in this imaging to suppress scattering, which limits the imaging depth to within several millimeters. It has been known that the so-called "biological window" with low loss for a biological tissue has been known to lie in the near-infrared (NIR) wavelength range between 1000 and 1700 nm. The use of fluorescence in the over-1000-nm (OTN) NIR can deepen the observation to several centimeters. The use of imaging devices based on semiconductor silicon has limited the wavelength of the fluorescence bioimaging to less than 1000 nm. However, the appearance of InGaAs CCD on the market, to allow for imaging of the OTN-NIR light, is now changing the situation. On the other hand, rare-earth doped ceramic nanophosphors (RED-CNP) can emit efficient fluorescence in the OTN-NIR wavelength range. The author's group has applied the RED-CNP to OTN-NIR fluorescence bioimaging by hybridizing the RED-CNP with various polymers or molecules. The present paper will review the development of the materials and systems for this OTN-NIR fluorescence bioimaging, together with some applications of the imaging method for biological research and a medical surgery. PMID:23449415

Soga, Kohei

2013-01-01

119

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

120

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~800 nm). A low threshold of ~12 mJ/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

121

Far-infrared laser magnetic resonance of vibrationally excited CD2  

NASA Technical Reports Server (NTRS)

The detection of 13 rotational transitions in the first excited bending state (010) of CD2 using the technique of far-infrared laser magnetic resonance spectroscopy is reported. Molecular parameters for this state are determined from these new data together with existing infrared observations of the v(2) band. Additional information on the ground vibrational state (000) is also provided by the observation of a new rotational transition, and this is combined with existing data to provide a refined set of molecular parameters for the CD2 ground state. One spectrum has been observed that is assigned as a rotational transition within the first excited symmetric stretching state (100) of CD2. These data will be of use in refining the structure and the potential function of the methylene radical.

Evenson, K. M.; Sears, T. J.; Mckellar, A. R. W.

1984-01-01

122

Clinical multiphoton and CARS microscopy  

NASA Astrophysics Data System (ADS)

We report on clinical CARS imaging of human skin in vivo with the certified hybrid multiphoton tomograph CARSDermaInspect. The CARS-DermaInspect provides simultaneous imaging of non-fluorescent intradermal lipid and water as well as imaging of two-photon excited fluorescence from intrinsic molecules. Two different excitation schemes for CARS imaging have been realized: In the first setup, a combination of fs oscillator and optical parametric oscillator provided fs-CARS pump and Stokes pulses, respectively. In the second setup a fs oscillator was combined with a photonic crystal fiber which provided a broadband spectrum. A spectral range out of the broadband-spectrum was selected and used for CARS excitation in combination with the residual fs-oscillator output. In both setups, in addition to CARS, single-beam excitation was used for imaging of two-photon excited fluorescence and second harmonic generation signals. Both CARS-excitation systems were successfully used for imaging of lipids inside the skin in vivo.

Breunig, H. G.; Weinigel, M.; Darvin, M. E.; Lademann, J.; König, K.

2012-02-01

123

Multiphoton fluorescence spectroscopy of flourescent bioprobes and biomolecules  

Microsoft Academic Search

Multi-photon fluorescence spectra of a number of commonly used biological probes were measured in this study. Significant spectral variation has been detected between single and multi- photon excitation. The result is important for the proper selection of spectral setting\\/dichroic beam splitter in the set- up of a multi-photon fluorescence microscope. The information can also be useful in the detection of

Ping-chin Cheng; Bai-Ling Lin; Fu-Jen Kao; Chi-Kuang Sun; Yung-Shun Wang; TzuMing Liu; YiMin Wang; JianCheng Chen; Mao-Kuo Huang; Iain Johnson

2000-01-01

124

Multi-Photon Laser Scanning Microscopy Using an Acoustic Optical Deflector  

Microsoft Academic Search

Multi-photon laser scanning microscopes have many advantages over single-photon systems. However, the speed and flexibility of currently available multi-photon microscopes are limited by the use of mechanical mirrors to steer pulsed radiation for fluorophore excitation. Here, we describe the multi-photon adaptation of a confocal microscope that uses an acoustic optical deflector (AOD) for beam steering. AODs are capable of very

James D. Lechleiter; Da-Ting Lin; Ilse Sieneart

2002-01-01

125

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.

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

2011-01-01

126

Multiphoton absorption is probably not the primary threshold damage mechanism for femtosecond laser pulse exposures in the retinal pigment epithelium  

NASA Astrophysics Data System (ADS)

Laser induced breakdown has the lowest energy threshold in the femtosecond domain, and is responsible for production of threshold ocular lesions. It has been proposed that multiphoton absorption may also contribute to ultrashort-pulse tissue damage, based on the observation that 33 fs, 810 nm pulse laser exposures caused more DNA breakage in cultured, primary RPE cells, compared to CW laser exposures delivering the same average power. Subsequent studies, demonstrating two-photon excitation of fluorescence in isolated RPE melanosomes, appeared to support the role of multiphoton absorption, but mainly at suprathreshold irradiance. Additional experiments have not found a consistent difference in the DNA strand breakage produced by ultrashort and CW threshold exposures. DNA damage appears to be dependent on the amount of melanin pigmentation in the cells, rather than the pulsewidth of the laser; current studies have found that, at threshold, CW and ultrashort pulse laser exposures produce almost identical amounts of DNA breakage. A theoretical analysis suggest that the number of photons delivered to the RPE melanosome during a single 33-fsec pulse at the ED50 irradiance is insufficient to produce multiphoton excitation. This result appears to exclude the melanosome as a locus for two- or three-photon excitation; however, a structure with a larger effective absorption cross-section than the melanosome may interact with the laser pulses. One possibility is that the nuclear chromatin acts as a unit absorber of photons resulting in DNA damage, but this does not explain the near equivalence of ultrashort and CW exposures in the comet assay model. This equivalence indicated that multiphoton absorption is not a major contributor to the ultrashort pulse laser damage threshold in the near infrared.

Glickman, Randolph D.; Johnson, Thomas E.

2004-07-01

127

Determining two-photon absorption cross sections via nonresonant multiphoton photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Multiphoton excitation of exogenous dyes and endogenous biochemical species has been used extensively for tissue diagnosis by fluorescence spectroscopy. Unfortunately, the majority of endogenous biochemical chromophores have low quantum yields, less than 0.2, therefore determining two-photon cross sections of weakly luminescencing molecules is difficult using two-photon fluorescence spectroscopy. Accurate determination of two-photon cross sections of these biochemicals could provide insight into fluorescence signal reduction caused by the absorption of excitation energy by non-target intracellular species. Non-resonant multiphoton photoacoustic spectroscopy (NMPPAS) is a novel technique we have developed for condensed matter measurements that has the potential for accurately determining two-photon absorption cross-sections of chemicals with small or non-existant fluorescence quantum yields. In this technique, near infrared light is used to generate an ultrasonic signal following a non-resonant two-photon excitation process. This ultrasonic wave is directly related to the non-radative relaxation of the chromophore of interest and is measured using a contact piezoelectric ultrasonic transducer. The signal from the ultrasonic transducer can then be used to calculate two-photon absorption cross sections. This paper will describe the validation of this technique by measuring the two-photon absorption cross- sections of well characterized chromophores such as rhodamine B and coumarin 1 in solution as well as riboflavin in a gelatin tissue phantom.

Kiser, John B.; Chandrasekharan, Nirmala; Cullum, Brian M.

2007-10-01

128

Energy transfers in Kr Xe mixtures following selective multiphotonic excitation of Kr(3P1). Temporal analysis in Kr Xe mixtures  

Microsoft Academic Search

This work deals with energy transfer from the resonant state Kr(3P1) to xenon. A pulsed, brief and selective excitation of the molecular state Kr2[1u(3P1)] was achieved with a dye laser. An electrometer was used to select the appropriate excitation wavelength in order to prevent ionization. In mixtures, instead of the continuum of krypton, when a small amount of xenon was

F. Marchal; P. Berejny; N. Sewraj; Y. Salamero; P. Millet

2004-01-01

129

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.

2008-03-01

130

High-resolution spectroscopy and dynamics of multiphoton processes in atoms and molecules. Annual summary report, 1 October 1985-30 September 1986  

Microsoft Academic Search

This report summarizes research on resonantly enhanced multiphoton absorption, dissociation, and ionization processes in atoms and molecules. Multiphoton processes were studied using from one to three independently tunable visible and\\/or UV laser beams in order to establish both the underlying physics and the high degree of selectivity of multiphoton processes. Measurements were made to probe both the formation of excited

P. M. Dehmer; J. L. Dehmer

1986-01-01

131

Mechanism of oxidative stress generation in cells by localized near-infrared femtosecond laser excitation  

NASA Astrophysics Data System (ADS)

We examined the effect of femtosecond (fs) and continuous wave (CW) lasers at near-infrared range on the creation of reactive oxygen species in a human liver cancer cell line. By controlling the mitochondria electron transport chain (ETC), it was found that a major part of the oxidative stress was generated by the laser induced thermal effect on the mitochondria while the remaining part was created by direct free electron liberation by the fs pulses, which could be observed after breaking the ETC. The study helps clarify the major effects produced on animal cells when excited by fs lasers.

He, Hao; Chan, Kam Tai; Kong, Siu Kai; Lee, Rebecca Kit Ying

2009-12-01

132

Laser action in chromium-activated forsterite for near-infrared excitation  

SciTech Connect

Recently, the authors reported room-temperature pulsed-laser action in chromium-activated forsterite (Cr:Mg/sub 2/SiO/sub 4/). The free-running laser output was centered at 1235 nm with a spectral bandwidth (full width at half-maximum,FWHM) of 22 nm. The laser emission was stimulated by the 532-nm excitation of the green-red absorption band of the system. The crystal is characterized by a shallow absorption band spanning the 850-1200-nm wavelength range, which overlaps a significant portion of the emission spectrum and was previously thought to inhibit laser action in that region. In this communication, laser action in chromium-doped forsterite for 1064-nm excitation of this band is reported. The near infrared absorption thus turns out to be effective in populating the initial level of the lasing transition.

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

1988-10-15

133

Multiphoton ionization and multiphoton resonances in the tunneling regime  

SciTech Connect

The rate of ionization of an atom of helium, argon, or hydrogen exposed to an intense monochromatic laser field and the quasienergy spectrum of their dressed states are studied for values of the Keldysh parameter between 1 and 0.6 and wavelengths between 390 and 1300 nm. The calculations are carried out within the non-Hermitian Floquet theory. Resonances with intermediate excited states significantly affect ionization from the dressed ground state at all the intensities and all the wavelengths considered. The dressed excited states responsible for these structures are large-{alpha}{sub 0} states akin to the Kramers-Henneberger states of the high-frequency Floquet theory. Within the single-active-electron approximation, these large-{alpha}{sub 0} states become species independent at sufficiently high intensity or sufficiently long wavelength. Apart for the resonance structures arising from multiphoton coupling with excited states, the ab initio Floquet ionization rate is in excellent agreement with the predictions of two different calculations in the strong field approximation, one based on a length-gauge formulation of this approximation and one based on a velocity-gauge formulation. The calculations also confirm the validity of the {omega}{sup 2} expansion as an alternative to the strong field approximation for taking into account the nonadiabaticity of the ionization process in intense low-frequency laser fields.

Potvliege, R. M.; Mese, E.; Vucic, Svetlana [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Department of Physics, University of Dicle, Diyarbakir, Turkey and Department of Chemistry, Durham University, Durham (United Kingdom); Institute of Physics, Pregrevica 118, 11080 Belgrade-Zemun (Serbia)

2010-05-15

134

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

135

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

136

Studies of atmospheric molecules by multiphoton spectroscopy  

SciTech Connect

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

Johnson, P.M.

1991-10-01

137

Excited-State Dynamics of Protochlorophyllide Revealed by Subpicosecond Infrared Spectroscopy  

PubMed Central

To gain a better understanding of the light-induced reduction of protochlorophyllide (PChlide) to chlorophyllide as a key regulatory step in chlorophyll synthesis, we performed transient infrared absorption measurements on PChlide in d4-methanol. Excitation in the Q-band at 630 nm initiates dynamics characterized by three time constants: ?1 = 3.6 ± 0.2, ?2 = 38 ± 2, and ?3 = 215 ± 8 ps. As indicated by the C13?=O carbonyl stretching mode in the electronic ground state at 1686 cm?1, showing partial ground-state recovery, and in the excited electronic state at 1625 cm?1, showing excited-state decay, ?2 describes the formation of a state with a strong change in electronic structure, and ?3 represents the partial recovery of the PChlide electronic ground state. Furthermore, ?1 corresponds with vibrational energy relaxation. The observed kinetics strongly suggest a branched reaction scheme with a branching ratio of 0.5 for the path leading to the PChlide ground state on the 200 ps timescale and the path leading to a long-lived state (>>700 ps). The results clearly support a branched reaction scheme, as proposed previously, featuring the formation of an intramolecular charge transfer state with ?25 ps, its decay into the PChlide ground state with 200 ps, and a parallel reaction path to the long-lived PChlide triplet state.

Colindres-Rojas, Miriam; Wolf, Matthias M.N.; Gross, Ruth; Seidel, Sonja; Dietzek, Benjamin; Schmitt, Michael; Popp, Jurgen; Hermann, Gudrun; Diller, Rolf

2011-01-01

138

Ion pair formation in multiphoton excitation of NO(2) using linearly and circularly polarized femtosecond light pulses: kinetic energy distribution and fragment recoil anisotropy.  

PubMed

The NO(2) ion pair photodissociation dynamics leading to NO(+)(X(1)Sigma(+),v) + O(-)((2)P(3/2) or (2)P(1/2)), induced by a 1 kHz femtosecond laser with wavelengths near 400 nm, has been characterized using the coincidence vector correlation method. The ion pair production after four-photon absorption reaches more than 15% of the primary ionization. The kinetic energy release of the fragments demonstrates a significant vibrational excitation of the NO(+)(X(1)Sigma(+),v) molecular fragment. Recoil ion fragment emission is strongly aligned along the polarization axis of linearly polarized light or preferentially emitted in the plane perpendicular to the propagation axis of circularly polarized light. The formalism describing the recoil anisotropy for bound-to-bound n-photon transition inducing prompt axial recoil dissociation of a nonlinear molecule has been developed to interpret the measured anisotropies in terms of excitation pathways via near-resonant intermediate states of specific symmetries. Possible reaction pathways are discussed that are consistent with the data and supported by calculations of potential energy surfaces and transition moments. PMID:20704179

Elkharrat, C; Picard, Y J; Billaud, P; Cornaggia, C; Garzella, D; Perdrix, M; Houver, J C; Lucchese, R R; Dowek, D

2010-09-16

139

High harmonics generation from excited states of atomic lithium  

NASA Astrophysics Data System (ADS)

We present a calculation of the harmonics yield from the lithium atom exposed to an intense 3.5 µm mid-infrared laser pulse. Our calculation shows that a considerable increase of the yield of high harmonics generation (HHG) can be achieved if initially the atom is prepared in an excited 2p state. We show that this increase can be regarded as a resonant process due to appearance of a multiphoton resonance between the initial state and a quasienergy state. We also consider HHG from lithium prepared initially in a superposition of the ground and excited states.

Ivanov, I. A.; Kheifets, A. S.

2008-06-01

140

Multiphoton ionization of atomic cesium  

SciTech Connect

We describe experimental studies of resonantly enhanced multiphoton ionization (MPI) of cesium atoms in the presence and absence of an external electric field. In the zero-field studies, photoelectron angular distributions for one- and two-photon resonantly enhanced MPI are compared with the theory of Tang and Lambropoulos. Deviations of experiment from theory are attributed to hyperfine coupling effects in the resonant intermediate state. The agreement between theory and experiment is excellent. In the absence of an external electric field, signal due to two-photon resonant three-photon ionization of cesium via np states is undetectable. Application of an electric field mixes nearby nd and ns levels, thereby inducing excitation and subsequent ionization. Signal due to two-photon excitation of ns levels in field-free experiments is weak due to their small photoionization cross section. An electric field mixes nearby np levels which again allows detectable photoionization signal. For both ns and np states the field induced MPI signal increases as the square of the electric field for a given principal quantum number and increases rapidly with n for a given field strength. Finally, we note that the classical two-photon field-ionization threshold is lower for the case in which the laser polarization and the electric field are parallel than it is when they are perpendicular. 22 references, 11 figures.

Compton, R.N.; Klots, C.E.; Stockdale, J.A.D.; Cooper, C.D.

1984-01-01

141

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

142

Design and commissioning of a directly coupled in-vivo multiphoton microscope for skin imaging in humans and large animals  

NASA Astrophysics Data System (ADS)

The application of near infrared multiphoton excitation to the laser-scanning microscope was first conceived by Denk, Strickler and Webb in 1990. Since then, advances in design have seen the multiphoton laser scanning microscope (MPLSM) applied to a wide range of biological research areas, including skin imaging and vaccine delivery. The technique has the attributes of low phototoxicity, high-resolution functional imaging to depths in scattered tissues. These characteristics have encouraged engineers and scientists to develop in-vivo imaging systems. For these applications, laser excitation pulses can be delivered to the sample through optical fibers. Although this solution provides a number of advantages relating to movement and flexibility of the site of interest relative to the laser source, the peak powers that can be delivered down the fiber are limited. We report on the design and commissioning of a directly coupled in-vivo MPM system, optimised for the imaging of epidermal vaccines delivered to a range of biological models and humans. Specifically, we seek to apply the system to visualise in-vivo, the influence of hand-held, helium powered needle-free systems on skin cells. A standard Nikon E600FN microscope, dissected above the optical plane was cantilevered from a vibration isolated table using rigid support arms. The modified microscope was coupled to an infrared optimised Bio-Rad Radiance 2100MP, multiphoton dedicated laser scanning control and image acquisition system. Femtosecond laser pulses were provided by a 10W Verdi pumped Mira Ti:Sapphire laser, from Coherent Inc. The microscope was modified such that the transmission half may be selectively attached for conventional imaging with ex-vivo and cell culture samples, or removed for in-vivo imaging of skin sites on the body of humans and large animals. Optical performance of the system, and aspects of its design and commissioning are discussed in this paper.

Mulholland, William J.; Kendall, Mark A.

2004-02-01

143

Live cell imaging by multifocal multiphoton microscopy.  

PubMed

Multifocal multiphoton microscopy (MMM) permits parallel multiphoton excitation by scanning an array of high numerical aperture foci across a plane in the sample. MMM is particularly suitable for live cell investigations since it combines advantages of standard multiphoton microscopy such as optical sectioning and suppression of out-of-focus phototoxicity with high recording speeds. Here we describe several applications of MMM to live cell imaging using the neuroendocrine cell line PC12 and bovine chromaffin cells. Stainings were performed with the acidophilic dye acridine orange and the lipophilic dyes FM1-43 and Fast DiA as well as by transfection of the cells with GFP. In both bovine chromaffin and PC12 cells structural elements of nuclear chromatin and the 3-D distribution of acidic organelles inside the cells were visualized. In PC12 cells differentiated by nerve growth factor examples of neurites were monitored. Stainings of membranes were used to reconstruct the morphology of cells and neurites in three dimensions by volume-rendering and by isosurface plots. 3-D reconstructions were composed from stacks of about 50 images each with a diameter of 30-100 microm that were acquired within a few seconds. We conclude that MMM proves to be a technically simple and very effective method for fast 3-D live cell imaging at high resolution. PMID:11089921

Straub, M; Lodemann, P; Holroyd, P; Jahn, R; Hell, S W

2000-10-01

144

Optimizing Fluorescence Collection Efficiency in Multiphoton Microscopy  

NASA Astrophysics Data System (ADS)

Over the past 20 years multiphoton microscopy has established itself as the premier modality for high resolution (<1um) deep tissue in vivo fluorescence imaging. The dramatic improvements in imaging performance when compared to more conventional techniques result from the use of longer wavelength excitation light (˜700--1000 nm), enabling deeper tissue penetration, and the spatially and temporally localized generation of fluorescence inherent in two-photon excitation, which virtually eliminates out-of-focus fluorescence. Imaging depths of ˜500 mum are now considered common practice, however, as the technique continues to increase in popularity and utility significant efforts are being made to maximize imaging depth. These efforts can be compartmentalized into those aimed at increasing fluorescence excitation and those attempting to maximize fluorescence collection. Progress has been made in increasing fluorescence excitation efficiency, however these approaches require costly and complicated optical instrumentation, and are often deemed impractical. Efforts targeted at increasing fluorescence collection efficiency have been limited due to the complexity of describing the ensemble of scattered fluorescent photons emerging from a sample and propagating through a microscope objective and the subsequent fluorescence collection pathway of a multiphoton microscope. Since there is no analytic solution for these fluorescent photon distributions as a function of imaging depth in the relevant, non-diffusive multiphoton imaging range, numerical techniques are required. Here is presented the first computational model of fluorescence propagation through the complete fluorescence collection pathway of a multiphoton microscope. Monte Carlo simulations were used to model the propagation of fluorescence as a function of imaging depth in a scattering sample with physiologically accurate optical properties, and to determine the collected and transmitted fluorescent fraction through the Olympus 20X 0.95NA microscope objective, one of the highest performance and most commonly used objectives for multiphoton imaging. It was determined that the complex trajectories of scattered photons entering the microscope objective emerge from the objective back aperture with a large spatio-angular distribution of fluorescence, which varies significantly with imaging depth and scattering length. Accurate determination of this distribution provided the information necessary to model, design, and fabricate a maximally efficient post-objective fluorescence collection pathway. Simulations corroborated by data from experimental tissue phantoms demonstrate collection efficiency improvements of 50--90% over conventional, non-optimized collection geometries at imaging depths of 1000 mum. Furthermore, the collection efficiency of the optimized system was found to be nearly constant over the entire imaging range (0--1000 mum), and only weakly dependent on the scattering length of the sample. In vivo imaging performance was verified by imaging YFP+ layer V neurons in mouse cortex to a depth of 850 mum. Optimizing the fluorescence collection system in multiphoton microscopy results in large gains in fluorescence collection efficiency which translate into increased imaging depth, higher resolution, and a decrease in required excitation power, thereby reducing the potential for photodamage and generation of background fluorescence. Imaging performance was found to be comparable to that of the complex techniques aimed at increasing fluorescence excitation, but far simpler to implement and at a cost roughly two orders of magnitude less.

Zinter, Joseph P.

145

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

NASA Astrophysics Data System (ADS)

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

Mukhopadhyay, Indranath

2004-06-01

146

Multi-Photon Nanosurgery in Live Brain  

PubMed Central

In the last few years two-photon microscopy has been used to perform in vivo high spatial resolution imaging of neurons, glial cells and vascular structures in the intact neocortex. Recently, in parallel to its applications in imaging, multi-photon absorption has been used as a tool for the selective disruption of neural processes and blood vessels in living animals. In this review we present some basic features of multi-photon nanosurgery and we illustrate the advantages offered by this novel methodology in neuroscience research. We show how the spatial localization of multi-photon excitation can be exploited to perform selective lesions on cortical neurons in living mice expressing fluorescent proteins. This methodology is applied to disrupt a single neuron without causing any visible collateral damage to the surrounding structures. The spatial precision of this method allows to dissect single processes as well as individual dendritic spines, preserving the structural integrity of the main neuronal arbor. The same approach can be used to breach the blood-brain barrier through a targeted photo-disruption of blood vessels walls. We show how the vascular system can be perturbed through laser ablation leading toward two different models of stroke: intravascular clot and extravasation. Following the temporal evolution of the injured system (either a neuron or a blood vessel) through time lapse in vivo imaging, the physiological response of the target structure and the rearrangement of the surrounding area can be characterized. Multi-photon nanosurgery in live brain represents a useful tool to produce different models of neurodegenerative disease.

Mascaro, Anna Letizia Allegra; Sacconi, Leonardo; Pavone, Francesco S.

2010-01-01

147

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

148

Laser Action in Chromium-Activated Forsterite for Near-Infrared Excitation: Is Cr4+ the Lasing Ion,  

National Technical Information Service (NTIS)

Room temperature pulsed laser action has been obtained in chromium activated forsterite (Cr:Mg2SiO4) for excitation of the near infrared absorption band of the system by the 1064 nm radiation from a Nd:YAG laser. The characteristics of laser emission are ...

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

1988-01-01

149

Additional P(3/2) and P(1/2) Infrared Excited State Lines of Gallium and Indium in Silicon.  

National Technical Information Service (NTIS)

Infrared excitation spectra were measured for the p3/2 lines of gallium in silicon. Two missing lines were observed, and a previous weak or doubtful one was confirmed. Spectra were also obtained of the p1/2 lines of gallium and indium in silicon, demonstr...

J. J. Rome R. J. Spry T. C. Chandler G. J. Brown B. C. Covington

1982-01-01

150

A novel flexible clinical multiphoton tomograph for early melanoma detection, skin analysis, testing of anti-age products, and in situ nanoparticle tracking  

NASA Astrophysics Data System (ADS)

High-resolution 3D microscopy based on multiphoton induced autofluorescence and second harmonic generation have been introduced in 1990. 13 years later, CE-marked clinical multiphoton systems for 3D imaging of human skin with subcellular resolution have first been launched by JenLab company with the tomography DermaInspect®. This year, the second generation of clinical multiphoton tomographs was introduced. The novel multiphoton tomograph MPTflex, equipped with a flexible articulated optical arm, provides an increased flexibility and accessibility especially for clinical and cosmetical examinations. Improved image quality and signal to noise ratio (SNR) are achieved by a very short source-drain spacing, by larger active areas of the detectors and by single photon counting (SPC) technology. Shorter image acquisition time due to improved image quality reduces artifacts and simplifies the operation of the system. The compact folded optical design and the light-weight structure of the optical head eases the handling. Dual channel detectors enable to distinguish between intratissue elastic fibers and collagenous structures simultaneously. Through the use of piezo-driven optics a stack of optical cross-sections (optical sectioning) can be acquired and 3D imaging can be performed. The multiphoton excitation of biomolecules like NAD(P)H, flavins, porphyrins, elastin, and melanin is done by picojoule femtosecond laser pulses from an tunable turn-key femtosescond near infrared laser system. The ability for rapid high-quality image acquisition, the user-friendly operation of the system and the compact and flexible design qualifies this system to be used for melanoma detection, diagnostics of dermatological disorders, cosmetic research and skin aging measurements as well as in situ drug monitoring and animal research.

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

2010-02-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

152

Multiphoton microscopic imaging of human normal and cancerous oesophagus tissue.  

PubMed

In this paper, microstructures of human oesophageal submucosa are evaluated using multiphoton microscopy, based on two-photon excited fluorescence and second harmonic generation. The content and distribution of collagen, elastic fibers and cancer cells in normal and cancerous submucosa layer have been distinctly obtained and briefly discussed. The variation of these components is very relevant to the pathology in oesophagus, especially in early oesophageal cancer. Our results further indicate that the multiphoton microscopy technique has the potential application in vivo in clinical diagnosis and monitoring of early oesophageal cancer. PMID:24236445

Chen, W S; Wang, Y; Liu, N R; Zhang, J X; Chen, R

2014-01-01

153

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

154

Multiphoton imaging with compact semiconductor disk lasers  

NASA Astrophysics Data System (ADS)

We present the performance of a compact, non expensive, easy to use ultrafast semiconductor disk laser (1W average power, 1.5 ps, 500MHz) for multiphoton imaging. The laser's operating wavelengths of 970 nm makes it ideal for nonlinear excitation of GFP as it has a two-photon action cross section peak at this wavelength. This property relaxes the required peak powers for TPEF imaging. We show the suitability of this laser for in-vivo imaging with GFP and other dyes; at different penetration depths; time-lapse studies and SHG imaging. The laser performance is evaluated in commercial microscopes and in comparison with Ti:sapphire lasers.

Loza-Alvarez, Pablo; Aviles-Espinosa, Rodrigo; Artigas-García, David; Hamilton, Craig; Malcolm, Graeme

2012-02-01

155

1D-scanning addressable multiregional multifocal multiphoton microscopy  

NASA Astrophysics Data System (ADS)

We developed a novel addressable multiregional multiphoton microscope that employs a fast one-dimensional discrete-line scanning approach based on a spatial light modulator (SLM). The phase-only SLM shapes an incoming mode-locked, near-infrared Ti:sapphire laser beam into multiple specific discrete-lines, which are designed according to the sizes and locations of the target samples. Only the target-sample areas of are scanned one-dimensionally, resulting in an efficient use of the laser's power. Compared with conventional multiphoton microscopies, this technique shortens scanning time and minimizes photodamage by concentrating scanning energy and dwell time on the areas of interest. Additionally, our discrete-line-focus design eliminates the cross-talk that occurs in conventional one-dimensional line-scanning multiphoton microscopes, thus enhancing the lateral and axial resolutions of the line-scanning imaging system.

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

2013-09-01

156

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

2011-02-01

157

Pulse-shaping multiphoton FRET microscopy  

PubMed Central

Fluorescence Resonance Energy Transfer (FRET) microscopy is a commonly-used technique to study problems in biophysics that range from uncovering cellular signaling pathways to detecting conformational changes in single biomolecules. Unfortunately, excitation and emission spectral overlap between the fluorophores create challenges in quantitative FRET studies. It has been shown previously that quantitative FRET stoichiometry can be performed by selective excitation of donor and acceptor fluorophores. Extending this approach to two-photon FRET applications is difficult when conventional femtosecond laser sources are used due to their limited bandwidth and slow tuning response time. Extremely broadband titanium:sapphire lasers enable the simultaneous excitation of both donor and acceptor for two-photon FRET, but do so without selectivity. Here we present a novel two-photon FRET microscopy technique that employs pulse-shaping to perform selective excitation of fluorophores in live cells and detect FRET between them. Pulse-shaping via multiphoton intrapulse interference can tailor the excitation pulses to achieve selective excitation. This technique overcomes the limitation of conventional femtosecond lasers to allow rapid switching between selective excitation of the donor and acceptor fluorophores. We apply the method to live cells expressing the fluorescent proteins mCerulean and mCherry, demonstrating selective excitation of fluorophores via pulse-shaping and the detection of two-photon FRET. This work paves the way for two-photon FRET stoichiometry.

Brenner, Meredith H.; Cai, Dawen; Nichols, Sarah R.; Straight, Samuel W.; Hoppe, Adam D.; Swanson, Joel A.; Ogilvie, Jennifer P.

2012-01-01

158

Spectral and lifetime fluorescence imaging microscopies: New modalities of multiphoton microscopy applied to tissue or cell engineering  

Microsoft Academic Search

Spectral and multiphoton imaging is the preferred approach for non-invasive study allowing deeper penetration to image molecular processes in living cells. But currently available fluorescence microscopic techniques based on fluorescence intensity, such as confocal or multiphoton excitation, cannot provide detailed quantitative information about the dynamic of complex cellular structure (molecular interaction). Due to the variation of the probe concentration, photostability,

D. Dumas; L. Grossin; B. Riquelmec; C. Gigant-Huselstein; P. Gillet; J. F. Stoltz; UHP-INPL-CHU Nancy

159

Multi-photon Polymerization of Waveguide Structures within Photonic Crystals  

NASA Astrophysics Data System (ADS)

The functionality of self-assembled photonic crystals will be greatly enhanced if complex features including wave guides and cavities are defined within the interior of the photonic crystal. Here we demonstrate one promising approach to create such features based on multiphoton polymerization of monomers contained within the interstitial space of colloidal crystals. Following assembly of the colloidal crystal and removal of solvent, the interstitial space was filled with an appropriate monomer photoactive dye system, such as trimethylolpropane triacrylate and Rose Bengal or even Norland Optical adhesive. The monomer was locally photopolymerized in a defined pattern via 2- and 3-photon excitation using a modified laser scanning confocal microscope and the near-infrared output of a Ti-Sapphire laser. After the desired pattern was polymerized, unpolymerized monomer was removed with solvent. The colloidal crystal matrix supports the polymerized features, thus no shrinkage or cracking was observed. This methodology enabled the fabrication of complex 3-D patterns within the colloidal crystal with a minimum feature size of 1 micrometer and is compatible with many techniques for creating high dielectric contrast photonic crystals including melt imbibing of chalcogenide glasses, electrodeposition of II-VI semiconductors, sol-gel, and nanoparticle deposition.

Braun, Paul

2002-03-01

160

Excitation of Extended Red Emission and Near-Infrared Continuum Radiation in the Interstellar Medium  

NASA Astrophysics Data System (ADS)

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 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 N with 20 <= N <= 28 atoms. The composition and structure of these molecules is discussed and IR band energies for several possible C 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 N )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.

2009-11-01

161

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

Microsoft Academic Search

We present visible and infrared images, 1.5 to 2.3 micrometer infrared spectra and (Fe II) 1.64 micrometer, H2 (1 - 0) S(1) 2.121 micrometer, and Brgamma 2.165 micrometer infrared line contour maps obtained to investigate the nature of the activity and the origin of the infrared line emission in two relatively nearby infrared luminous galaxies. NGC 3256 is a merging

A. F. M. Moorwood; E. Oliva

1994-01-01

162

Improvement of depth resolution on photoacoustic imaging using multiphoton absorption  

NASA Astrophysics Data System (ADS)

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

Yamaoka, Yoshihisa; Fujiwara, Katsuji; Takamatsu, Tetsuro

2007-07-01

163

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

164

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

Microsoft Academic Search

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

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

2011-01-01

165

Photochemistry of UV-excited trifluoroacetylacetone and hexafluoroacetylacetone I: infrared spectra of fluorinated methylfuranones formed by HF photoelimination.  

PubMed

The photochemistry of gas-phase 1,1,1-trifluoroacetylacetone (TFAA) excited with ultraviolet (UV) light involves a significant photoelimination channel that produces hydrogen fluoride and a fluorinated methylfuranone, 2,2-difluoro-5-methyl-3(2H)-furanone (2FMF). This pathway is remarkable because it is a gas-phase unimolecular reaction that forms a five-membered ring product. This report is the first of such a TFAA photoelimination channel, which is similar to one observed with 1,1,1,5,5,5-hexafluoroacetylacetone (HFAA), resulting in 2,2-difluoro-5-trifluoromethyl-3(2H)-furanone. We present infrared spectral observations of 2FMF produced by pulsed, UV-laser excitation of TFAA, along with analogous results from HFAA, supported by density functional theory (DFT) computational studies. DFT results for the infrared spectrum of 5-methyl-3(2H)-furanone, the expected comparable acetylacetone photoelimination product, help suggest that UV excitation of acetylacetone fails to follow a similar type of photoelimination. We use a weighted RMS approach as a figure of merit for comparing calculated infrared frequencies with experimental data. Results from the three acetylacetones reveal how the presence of fluorine atoms in acetylacetone influences the gas-phase molecular photochemistry. PMID:23176295

Muyskens, Karen J; Alsum, Joel R; Thielke, Timothy A; Boer, Jodi L; Heetderks, Tina R; Muyskens, Mark A

2012-12-20

166

Time-resolved femtosecond optical characterization of multi-photon absorption in high-pressure-grown Al0.86Ga0.14N single crystals  

NASA Astrophysics Data System (ADS)

We report our experimental studies on time-resolved pump-probe spectroscopy in high-quality Al0.86Ga0.14N single crystals, grown using a solution technique in a high-nitrogen-gas-pressure system. Our optical measurements were performed using a non-traditional, two-beam [one ultraviolet (UV) and one infrared (IR)], femtosecond pump-probe approach, in which the photon energies of both beams were below the bandgap of the sample and each electron-hole pair was generated by a multi-photon process of absorption of a pump photon together with another photon produced by second harmonic generation from two probe photons. Temporal scanning of the probe while monitoring the normalized transient differential transmissivity (?T/T) signal, produced a 310-fs-wide, Gaussian-shaped correlation signal caused by the multi-photon absorption process, followed by a >100-ps-long relaxation of photo-excited carriers. By studying the ?T/T correlation signal amplitude dependence on the pump-power intensity and wavelength, the multi-photon absorption was determined to be predominantly caused by absorption of a pump photon and a second harmonic photon from the probe.

Zhang, Jie; Belousov, Andrey; Karpi?ski, Janusz; Batlogg, Bertram; Wicks, Gary; Sobolewski, Roman

2011-12-01

167

Enhanced detection of myeloperoxidase activity in deep tissues through luminescent excitation of near-infrared nanoparticles.  

PubMed

A previous study reported the use of luminol for the detection of myeloperoxidase (MPO) activity using optical imaging in infiltrating neutrophils under inflammatory disease conditions. The detection is based on a photon-emitting reaction between luminol and an MPO metabolite. Because of tissue absorption and scattering, however, luminol-emitted blue light can be efficiently detected from superficial inflammatory foci only. In this study we report a chemiluminescence resonance energy transfer (CRET) methodology in which luminol-generated blue light excites nanoparticles to emit light in the near-infrared spectral range, resulting in remarkable improvement of MPO detectability in vivo. CRET caused a 37-fold increase in luminescence emission over luminol alone in detecting MPO activity in lung tissues after lipopolysaccharide challenge. We demonstrated a dependence of the chemiluminescent signal on MPO activity using MPO-deficient mice. In addition, co-administration of 4-aminobenzoic acid hydrazide (4-ABAH), an irreversible inhibitor of MPO, significantly attenuated luminescent emission from inflamed lungs. Inhibition of nitric oxide synthase with a nonspecific inhibitor, L-NAME, had no effect on luminol-mediated chemiluminescence production. Pretreatment of mice with MLN120B, a selective inhibitor of IKK-2, resulted in suppression of neutrophil infiltration to the lung tissues and reduction of MPO activity. We also demonstrated that CRET can effectively detect MPO activity at deep tissue tumor foci due to tumor development-associated neutrophil infiltration. We developed a sensitive MPO detection methodology that provides a means for visualizing and quantifying oxidative stress in deep tissue. This method is amenable to rapid evaluation of anti-inflammatory agents in animal models. PMID:23455711

Zhang, Ning; Francis, Kevin P; Prakash, Arun; Ansaldi, Daniel

2013-04-01

168

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

PubMed Central

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

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

2010-01-01

169

Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of benzo[g,h,i]perylene.  

PubMed

We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[g,h,i]perylene (BghiP) via resonantly enhanced multiphoton ionization (REMPI). Our analysis concentrates on the vibrational modes of both the first electronically excited state and the ground cationic state. Extensive vibronic coupling due to a nearby electronically excited state manifests through strong Franck-Condon (FC) forbidden bands, which are stronger than even the FC allowed bands in the REMPI spectrum. Theoretical calculations using Gaussian are problematic in identifying the electronic configurations of the excited electronic states and predicting the transition energies. However, by setting the keyword for the second excited electronic state, both density functional theory and configuration interaction methods can reproduce the observed spectrum qualitatively. The general agreement significantly helps with the vibrational assignment. The ZEKE spectra demonstrate propensity in preserving the vibrational excitation of the intermediate electronic state. In addition, almost all ZEKE spectra exhibit a similar vibrational distribution, and the distribution can be reproduced by an FC calculation from the vibronic origin of the first excited electronic state to the cationic state using Gaussian 09. These results suggest a remarkable structural stability of BghiP in accommodating the additional charge. All observed vibrational bands of the cation are IR active, establishing the role of ZEKE spectroscopy in mapping out far-infrared bands for astrophysical applications. PMID:22260341

Zhang, Jie; Harthcock, Colin; Kong, Wei

2012-02-16

170

Novel infrared spectra for intermolecular dihydrogen bonding of the phenol-borane-trimethylamine complex in electronically excited state.  

PubMed

The intermolecular dihydrogen bonding in the electronically excited states of the dihydrogen-bonded phenol-BTMA complex in gas phase was theoretically investigated using the time-dependent density functional theory method for the first time. It was theoretically demonstrated that the S(1) state of the dihydrogen-bonded phenol-BTMA complex is a locally excited state, in which only the phenol moiety is electronically excited. The infrared spectra of the dihydrogen-bonded phenol-BTMA complex in ground state and the S(1) state were calculated at both the O-H and B-H stretching vibrational regions. A novel infrared spectrum of the dihydrogen-bonded phenol-BTMA complex in the electronically excited state was found. The stretching vibrational absorption bands of the dihydrogen-bonded O-H and B-H groups are very strong in the ground state, while they are disappeared in the S(1) state. At the same time, a new strong absorption band appears at the C[Double Bond]O stretching region. From the calculated bond lengths, it was found that both the O-H and B-H bonds in the dihydrogen bond O-H...H-B are significantly lengthened in the S(1) state of the dihydrogen-bonded phenol-BTMA complex. However, the C-O bond in the phenol moiety is markedly shortened in the excited state, and then has the characteristics of C[Double Bond]O group. Furthermore, it was demonstrated that the intermolecular dihydrogen bonds in the electronically excited state of the dihydrogen-bonded phenol-BTMA complex are strengthened, since calculated H...H distance is drastically shortened in the S(1) state. PMID:17640127

Zhao, Guang-Jiu; Han, Ke-Li

2007-07-14

171

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

172

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

173

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

174

Multiphoton Interference as a Tool to Observe Families of Multiphoton Entangled States  

Microsoft Academic Search

Spontaneous parametric downconversion in combination with linear optics was successfully used to observe a variety of multiphoton entangled states. Yet, experiments performed so far lacked flexibility, as each of the various setups was useful for only a particular multiphoton entangled state. In this paper, we describe how, by using multiphoton interference, one can observe entire families of multiphoton entangled states

Witlef Wieczorek; Nikolai Kiesel; Christian Schmid; W. Laskowski; M. Zukowski; H. Weinfurter

2009-01-01

175

Developing compact multiphoton systems using femtosecond fiber lasers  

PubMed Central

We implement a fiber-delivered compact femtosecond fiber laser at 1030-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 200×160×45 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.

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

2010-01-01

176

Multi-Photon Entanglement and Quantum Teleportation.  

National Technical Information Service (NTIS)

The project 'Multi-Photon Entanglement and Quantum Teleportation' concerns a series of experimental and theoretical investigations on multi-photon entangled states and the applications, for example, quantum teleportation. The objective of this re search i...

Y. Shih

1999-01-01

177

Multiphoton Production and Detection of Atoms.  

National Technical Information Service (NTIS)

The production of atomic fragments from a compound using multiphoton dissociation was investigated for metal centered and hetero atom centered compounds. The atoms were detected by multiphoton ionization. Metal centered systems generated large amounts of ...

P. C. Engelking

1985-01-01

178

Enhancement of visible He2 emission by infrared laser excitation of He metastable atoms in atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

We observed bright red emission at an intersection of an infrared (IR) laser beam and an atmospheric-pressure plasma jet (APPJ). The APPJ had a coaxial dielectric barrier discharge configuration and generated a plasma plume in a He gas flow ejected into air from a glass capillary. Although the laser-beam wavelength was 1083 nm corresponding to He I (23P-23S) atomic transition, the enhanced red emission peaked in the visible region at 640 nm and had broad bandwidth corresponding to He2 (d\\,^{3}\\!\\Sigma_u^{+}{{--}}b\\,^{3}\\Pi _g) molecular transition. This result indicates that the IR laser excitation of He metastable (23S) atoms leads to selective formation of excited He2 (d\\,^{3}\\!\\Sigma_u^{+}) molecules from excited He (23P) atoms. The 640 nm emission intensity decreased as the laser beam moved downstream in the plasma plume, because of the quenching effects on the excited He atoms and the excited He2 molecules by air entrainment. We believe that the He2 (d\\,^{3}\\!\\Sigma_u^{+}) molecular formation follows two potential curves of He2 (f 3?u or f 3?u) and (d\\,^{3}\\!\\Sigma_u^{+}) states, overcoming a potential hump by three-body collision processes.

Urabe, Keiichiro; Motomura, Hideki; Sakai, Osamu; Tachibana, Kunihide

2011-02-01

179

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

180

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

181

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.

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

2009-01-01

182

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

183

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

PubMed Central

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

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

2013-01-01

184

Surface-enhanced Raman scattering on aluminum using near infrared and visible excitation.  

PubMed

We observed strong surface-enhanced Raman scattering on discontinuous nanostructured aluminum films using 785 nm excitation even though dielectric constants of this metal suggest plasmon supported spectroscopy in the ultraviolet range. The excitation of SERS correlates with plasmon resonances in the 1.3-2.5 eV range identified in electron energy loss spectra. PMID:24577020

Mogensen, Klaus Bo; Gühlke, Marina; Kneipp, Janina; Kadkhodazadeh, Shima; Wagner, Jakob B; Palanco, Marta Espina; Kneipp, Harald; Kneipp, Katrin

2014-04-11

185

Suppression of Recollision-Excitation Ionization in Nonsequential Double Ionization of Molecules by Mid-Infrared Laser Pulses  

NASA Astrophysics Data System (ADS)

The electron dynamics in strong field non-sequential double ionization of nitrogen molecules is investigated with the three-dimensional (3D) classical ensemble model. The numerical results show that the longitudinal momentum spectrum of the doubly charged ions evolves from a wide single-hump structure at the near-infrared (NIR) regime into a double-hump structure when the wavelength enters the mid-infrared (MIR) regime. Back analysis reveals that in the MIR regime, the recollision excitation with subsequent ionization (RESI) is strongly suppressed with increasing wavelength, which results in the double-hump structure of the ions momentum spectra. This double-hump structure becomes more pronounced as the wavelength further increases because the contribution of the RESI further decreases.

Zhang, Dong-Ling; Tang, Qing-Bin; Gao, Yang

2013-02-01

186

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

NASA Astrophysics Data System (ADS)

Porous Nd2(SiO4)3 nanoparticles were successfully synthesized by a controlled route. This kind of silicate nanoparticle could be excited by near-infrared (NIR) radiation (808 nm) and triggered a NIR emission (1066 nm) at room temperature. By monitoring the 1066 nm emission, the long-lived luminescent lifetime was determined to be 19.5 µs. These NIR nanoparticles with appropriate diameters (<100 nm) were suitable for cell assays. MTT assays showed that the cytotoxicity of the porous Nd2(SiO4)3 nanoparticles was very low. Therefore, these porous silicate nanoparticles are potential biosafe high-performance NIR biolabeling materials.

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

2011-05-01

187

Laser action in chromium-activated forsterite for near-infrared excitation: Is Cr/sup 4 +/ the lasing ion  

SciTech Connect

Room-temperature pulsed laser action has been obtained in chromium-activated forsterite (Cr:Mg/sub 2/SiO/sub 4/) for excitation of the near-infrared absorption band of the system by the 1064 nm radiation from a Nd:YAG laser. The characteristics of laser emission are similar to those observed for 532 nm pumping. It is suggested that the laser action is due to a ''center'' other than the trivalent chromium (Cr/sup 3 +/), presumably the tetravalent chromium (Cr/sup 4 +/).

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

1988-12-26

188

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.

Hoover, Erich E.; Squier, Jeff A.

2013-01-01

189

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

NASA Technical Reports Server (NTRS)

In this study, we explore the link between the physical properties of the outflow as determined from optical imaging and spectroscopy, and compare these results with those obtained from observations in the near infrared.

Noreiga-Crespo, A.; Ayala, S.; Garnavich, P.; Curiel, S.; Raga, A.; Bohm, K.; Raymond, J.

2000-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

191

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

PubMed

Upon excitation in thin oxide films by infrared radiation, radiative polaritons are formed with complex angular frequency ?, according to the theory of Kliewer and Fuchs (1966 Phys. Rev. 150 573). We show that radiative polaritons leak radiation with frequency ?(i) to the space surrounding the oxide film. The frequency ?(i) is the imaginary part of ?. The effects of the presence of the radiation leaked out at frequency ?(i) are observed experimentally and numerically in the infrared spectra of La(2)O(3) films on silicon upon excitation by infrared radiation of the 0TH type radiative polariton. The frequency ?(i) is found in the microwave to far infrared region, and depends on the oxide film chemistry and thickness. The presented results might aid in the interpretation of fine structures in infrared and, possibly, optical spectra, and suggest the study of other similar potential sources of electromagnetic radiation in different physical scenarios. PMID:23221332

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

2013-01-23

192

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

193

Two-color multiphoton ionization of xenon  

SciTech Connect

Two independently tunable, linearly polarized dye lasers have been used to study multiphoton ionization of gaseous xenon. One laser is tuned near three-photon resonance with the allowed 6s(3/2)/sup degree//sub J/ = 1 resonance, which is not observed with one laser at these pressures because of the destructive interference between the three-photon-excitation and third-harmonic-excitation pathways to the 6s(3/2)/sup degree//sub J/ = 1 state. The second laser is tuned to resonance with higher allowed np and np' sstates of xenon. The missing ionization signal is seen to be dramatically restored by the addition of the second laser beam; however, the signal again disappears as the pressure is increased. These results are discussed in relation to recent experimental and theoretical studies of cancellation effects between three-photon excitation and third-harmonic generation. Spectroscopic information obtained from tuning each dye laser, together with data on the angular distributions resulting from rotating the plane of polarization of one laser relative to that of the second laser, clearly shows that two different ionization mechanisms are operative. In addition, these experiments unambiguously illustrate the importancce of dissociative ionization of quasi-dimers of xenon over a rather broad frequency range.

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

1985-02-01

194

Study of crystal-field excitations and infrared active phonons in the multiferroic hexagonal DyMnO3.  

PubMed

In hexagonal DyMnO3, Dy(3+) crystal-field excitations are studied as a function of temperature and applied magnetic field. They are complemented with the measurements of infrared active phonon frequency shifts under applied magnetic field at T = 4.2 K. Between TN = 68 K and T = 10 K, the absence of Dy(3+) Kramers doublet splittings at either the C3 or the C3v site symmetries indicates that the Mn(3+) magnetic order effective exchange field has no component parallel to the c-axis at either site. Below T = 10 K, the ground state Kramers doublet splits under the Dy(3+) internal effective field as well as the applied magnetic field. Also, relatively strong infrared active phonon energy shifts are observed in magneto-infrared reflectance measurements at T = 4.2 K, allowing the calculation of the induced electric polarization changes as a function of the applied magnetic field. Such changes are associated with a large magnetoelectric effect in DyMnO3, arising from a charge transfer between Dy(3+) and apical oxygen ions. PMID:24172650

Jandl, S; Mansouri, S; Vermette, J; Mukhin, A A; Ivanov, V Yu; Balbashov, A; Orlita, M

2013-11-27

195

Imaging cells and extracellular matrix in vivo by using second-harmonic generation and two-photon excited fluorescence  

Microsoft Academic Search

Multiphoton microscopy relies on nonlinear light-matter interactions to provide contrast and optical sectioning capability for high-resolution imaging. Most multiphoton microscopy studies in biological systems have relied on two-photon excited fluorescence (TPEF) to produce images. With increasing applications of multiphoton microscopy to thick-tissue \\

Aikaterini Zoumi; Alvin Yeh; Bruce J. Tromberg

2002-01-01

196

Photoacoustic imaging of a near-infrared fluorescent marker based on dual wavelength pump-probe excitation  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging has been used to determine the spatial distribution of fluorophores, such as exogenous dyes and genetically expressed proteins, from images acquired in phantoms and in vivo. Most methods involve the acquisition of multiwavelength images and rely on differences in the absorption spectra of the tissue chromophores to estimate the spatial distribution and abundance of the latter using spectral decomposition techniques, such as model based inversion schemes. However, the inversion of 3-D images can be computationally expensive. Experimental approaches to localising contrast agents may therefore be useful, especially if quantification is not essential. This work aims to develop a method for determining the spatial distribution of a near-infrared fluorescent cell marker from images acquired using dual wavelength excitation. The excitation wavelengths coincided with the absorption and emission spectrum of the fluorophore. The contrast mechanism relies on reducing the excited state lifetime of the fluorophore by inducing stimulated emission. This changes the amount of energy thermalized by the fluorophore, and hence the photoacoustic signal amplitude. Since this is not observed in endogenous chromophores, the background may be removed by subtracting two images acquired with and without pulse delay between the pump and probe pulses. To characterise the fluorophore, the signal amplitude is measured in a cuvette as a function of pulse delay, concentration, and fluence. The spatial distribution of the fluorophore is determined from images acquired in realistic tissue phantoms. This method may be suitable for in vivo applications, such as imaging of exogenous or genetically expressed fluorescent cell markers.

Märk, Julia; Theiss, Christoph; Schmitt, Franz-Josef; Laufer, Jan

2014-03-01

197

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

198

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

199

Effect of an additional infrared excitation on the luminescence efficiency of a single InAs/GaAs quantum dot  

NASA Astrophysics Data System (ADS)

Microphotoluminescence (PL) spectra of a single InAs/GaAs self-assembled quantum dot (QD) are studied under the main excitation of electron-hole pairs in the wetting layer (WL) and an additional infrared (IR) laser illumination. It is demonstrated that the IR laser with fixed photon energy well below the QD ground state induces striking changes in the spectra for a range of excitation energies and powers of the two lasers. For the main excitation above a threshold energy, defined as the onset of transitions between shallow acceptors and the conduction band in GaAs, the addition of the IR laser will induce a considerable increase in the QD emission intensity. This is explained in terms of additional generation of extra electrons and holes into the QD by the two lasers. For excitation below the threshold energy, the carrier capture efficiency from the WL into the QD is suggested to be essentially determined by the internal electric-field-driven carrier transport in the plane of the WL. The extra holes, generated in the GaAs by the IR laser, are supposed to effectively screen the built-in field, which results in a considerable reduction of the carrier collection efficiency into the QD and, consequently, a decrease of the QD PL intensity. A model is presented which allows estimating the magnitude of the built-in field as well as the dependence of the observed increase of the QD PL intensity on the powers of the two lasers. The use of an additional IR laser is considered to be helpful to effectively manipulate the emission efficiency of the quantum dot, which could be used in practice in quantum-dot-based optical switches.

Moskalenko, E. S.; Donchev, V.; Karlsson, K. F.; Holtz, P. O.; Monemar, B.; Schoenfeld, W. V.; Garcia, J. M.; Petroff, P. M.

2003-10-01

200

High-pressure infrared spectroscopy: Tuning of the low-energy excitations in correlated electron systems  

Microsoft Academic Search

We have extended the range of the high-pressure optical spectroscopy to the far-infrared region keeping the accuracy of ambient-pressure experiments. The developed method offers a powerful tool for the study of pressure-induced phase transitions and electronic-structural changes in correlated electron systems as the optical pressure cell, equipped with large free-aperture diamond window, allows the measurement of optical reflectivity down to

I. Kézsmárki; R. Gaál; C. C. Homes; B. Sípos; H. Berger; S. Bordács; G. Mihály; L. Forró

2007-01-01

201

High-pressure infrared spectroscopy: tuning of the low-energy excitations in correlated electron systems  

Microsoft Academic Search

We have extended the range of the high-pressure optical spectroscopy to the far-infrared region keeping the accuracy of ambient-pressure experiments. The newly-developed method offers a pow- erful tool for the study of pressure-induced phase transitions and electronic-structural changes in correlated electron systems. The novel-type optical pressure cell, equipped with large free-aperture diamond window, allows the measurement of optical reflectivity down

I. Kezsmarki; R. Gaal; C. C. Homes; B. S ´ õpos; H. Berger; S. Bordacs; G. Mihaly; L. Forro

202

Population transfer by multiphoton adiabatic rapid passage  

Microsoft Academic Search

The population of atoms in Rydberg states is efficiently transferred with a change in principal quantum number n of up to ten via multiphoton adiabatic rapid passage through a single multiphoton resonance using a frequency-chirped microwave pulse. A quantum-mechanical picture of multiphoton adiabatic rapid passage in a one-dimensional atom using a Floquet approach provides a good description of most, but

H. Maeda; J. H. Gurian; T. F. Gallagher

2011-01-01

203

Far-infrared optical excitations in multiferroic TbMnO3  

NASA Astrophysics Data System (ADS)

We provide a detailed study of the reflectivity of multiferroic TbMnO3 for wave numbers from 40 cm-1 to 1000 cm-1 and temperatures 5 K < T < 300 K. Excitations are studied for polarization directions E || a, the polarization where electromagnons are observed, and for E || c, the direction of the spontaneous polarization in this material. The temperature dependencies of eigenfrequencies, damping constants and polar strengths of all modes are studied and analyzed. For E || a and below the spiral ordering temperature of about 27 K we observe a transfer of optical weight from phonon excitations to electromagnons, which mainly involves low-frequency phonons. For E || c an unusual increase of the total polar strength and hence of the dielectric constant is observed indicating significant transfer of dynamic charge probably within manganese-oxygen bonds on decreasing temperatures.

Schmidt, M.; Kant, Ch.; Rudolf, T.; Mayr, F.; Mukhin, A. A.; Balbashov, A. M.; Deisenhofer, J.; Loidl, A.

2009-10-01

204

Two-photon fluorescence excitation in continuous-wave infrared optical tweezers  

NASA Astrophysics Data System (ADS)

We report the observation of two-photon fluorescence excitation in a continuous-wave (cw) single-beam gradient force optical trap and demonstrate its use as an in situ probe to study the physiological state of an optically confined sample. In particular, a cw Nd:YAG (1064-nm) laser is used simultaneously to confine, and excite visible fluorescence from submicrometer regions of, cell specimens. Two-photon fluorescence emission spectra are presented for motile human sperm cells and immotile Chinese hamster ovary cells that have been labeled with nucleic acid (Propidium Iodide) and pH-sensitive (Snarf) fluorescent probes. The resulting spectra are correlated to light-induced changes in the physiological state experienced by the trapped cells. This spectral technique should prove extremely useful for monitoring cellular activity and the effects of confinement by optical tweezers.

Liu, Y.; Sonek, G. J.; Berns, M. W.; Konig, K.; Tromberg, B. J.

1995-11-01

205

Chaos and incoherence in a classical rotation-vibration model of infrared multiple-photon excitation  

SciTech Connect

By including rotations in a previously developed generic vibrational model of ir multiple-photon excitation (MPE) (Phys. Rev. Lett. 51, 1259 (1983) and Phys. Rev. A 34, 1211 (1986)) it is found that the combination of chaotic dynamics and rotational averaging leads to fluence-dependent absorption and removes the sensitivity of the results to model-dependent parameters. Therefore, a complete propagation calculation through a molecular medium of this type would show a Beer's law absorption of photons consistent with the vast majority of MPE experiments performed to date, a result which previously was attributed to rate-equation dynamics in the molecular quasicontinuum. In addition, the classical rotation-vibration dynamics observed in this model correlate very well with one's quantum intuition based on a molecule's P-, Q-, and R-branch structure and on the red shift of the vibrational absorption feature with excitation.

Ackerhalt, J.R.; Milonni, P.W.

1988-03-01

206

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

207

Multiphoton processes of CO at 230 nm.  

PubMed

High resolution kinetic energy release spectra were obtained for C(+) and O(+) from CO multiphoton ionization followed by dissociation of CO(+). The excitation was through the CO (B (1)Sigma(+)) state via resonant two-photon excitation around 230 nm. A total of 5 and 6 photons are found to contribute to the production of carbon and oxygen cations. DC slice and Megapixel ion imaging techniques were used to acquire high quality images. Major features in both O(+) and C(+) spectra are assigned to the dissociation of some specific vibrational levels of CO(+)(X (2)Sigma(+)). The angular distributions of C(+) and O(+) are very distinct and those of various features of C(+) are also different. A dramatic change of the angular distribution of C(+) from dissociation of CO(+)(X (2)Sigma(+), nu(+) = 1) is attributed to an accidental one-photon resonance between CO(+)(X (2)Sigma(+), nu(+) = 1) and CO(+)(B (2)Sigma(+), nu(+) = 0) and explained well by a theoretical model. Both kinetic energy release and angular distributions were used to reveal the underlying dynamics. PMID:16880907

Li, Wen; Lahankar, Sridhar A; Huang, Cunshun; Shternin, Peter S; Vasyutinskii, Oleg S; Suits, Arthur G

2006-07-01

208

Multiphoton ionization of cesium through resonant dissociate states of Cs2  

Microsoft Academic Search

The multiphoton excitation of cesium through potentially resonant continuum molecular states was investigated over the 6200 to 5000 A wavelength region with a tunable dye laser source having a 0.06 to 0.08 A linewidth and a space charge ionization detector sensitive to a few ions per second. Conditions are established under which the lifetime of the resonant intermediate state against

M. Y. Mirza

1974-01-01

209

Multiphoton Dissociation of UF6 at lambda = 16 mu m in Supersonic Jets.  

National Technical Information Service (NTIS)

The multiple photon excitation of UF6 at 16 mu m has been studied in a number of laboratories, in view of its potential applications in uranium enrichment, using various schemes. Results are reported on two-frequency multiphoton dissociation of UF6 cooled...

M. Gilbert J. M. Weulersse P. Isnard G. Salvetat

1986-01-01

210

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.

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

1999-01-01

211

Femtosecond laser pulse optimization for multiphoton cytometry and control of fluorescence  

NASA Astrophysics Data System (ADS)

This body of work encompasses optimization of near infrared femtosecond laser pulses both for enhancement of flow cytometry as well as adaptive pulse shaping to control fluorescence. A two-photon system for in vivo flow cytometry is demonstrated, which allows noninvasive quantification of circulating cell populations in a single live mouse. We monitor fluorescently-labeled red blood cells for more than two weeks, and are also able to noninvasively measure circulation times of two distinct populations of breast cancer cells simultaneously in a single mouse. We build a custom laser excitation source in the form of an extended cavity mode-locked oscillator, which enables superior detection in whole blood or saline of cell lines expressing fluorescent proteins including the green fluorescent protein (GFP), tdTomato and mPlum. A mathematical model explains unique features of the signals. The ability to distinguish different fluorescent species is central to simultaneous measurement of multiple molecular targets in high throughput applications including the multiphoton flow cytometer. We demonstrate that two dyes which are not distinguishable to one-photon measurements can be differentiated and in fact quantified in mixture via phase-shaped two-photon excitation pulses found by a genetic algorithm. We also selectively enhance or suppress two-photon fluorescence of numerous common dyes with tailored pulse shapes. Using a multiplicative (rather than ratiometric) fitness parameter, we are able to control the fluorescence while maintaining a strong signal. With this method, we control the two-photon fluorescence of the blue fluorescent protein (BFP), which is of particular interest in investigations of protein-protein interactions, and has frustrated previous attempts of control. Implementing an acousto-optic interferometer, we use the same experimental setup to measure two-photon excitation cross-sections of dyes and prove that photon-photon interferences are the predominant mechanism of control. This research establishes the basis for molecularly tailored pulse shaping in multiphoton flow cytometry, which will advance our ability to probe the biology of circulating cells during disease progression and response to therapy.

Tkaczyk, Eric Robert

212

Development of near-infrared 35 fs laser microscope and its application to the detection of three- and four-photon fluorescence of organic microcrystals.  

PubMed

Femtosecond near-infrared laser microscope was developed with a home-built cavity-dumped chromium:forsterite laser as a light source centered at 1.26 microm. Optimization of the pulse duration achieved 35 fs fwhm at the sample position of the microscope after passing through a 100x objective. This system was applied to the detection of multiphoton fluorescence of some organic microcrystals. Excitation intensity dependence and the interferometric autocorrelation detection of the fluorescence clearly demonstrated that simultaneous three- and four-photon absorption processes are responsible for the production of the excited state for perylene and anthracene microcrystals, respectively. The spatial resolution along the optical axis and its dependence on the order of the multiphoton process were also discussed. PMID:16471646

Matsuda, Hirohisa; Fujimoto, Yousuke; Ito, Syoji; Nagasawa, Yutaka; Miyasaka, Hiroshi; Asahi, Tsuyoshi; Masuhara, Hiroshi

2006-01-26

213

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

214

Critical evaluation of a handheld Raman spectrometer with near infrared (785nm) excitation for field identification of minerals.  

PubMed

Handheld Raman spectrometers (Ahura First Defender XL, Inspector Raman DeltaNu) permit the recording of acceptable and good quality spectra of a large majority of minerals outdoors and on outcrops. Raman spectra of minerals in the current study were obtained using instruments equipped with 785 nm diode lasers. Repetitive measurements carried out under an identical instrumental setup confirmed the reliability of the tested Raman spectrometers. Raman bands are found at correct wavenumber positions within ±3 cm(-1) compared to reference values in the literature. Taking into account several limitations such as the spatial resolution and problems with metallic and black and green minerals handheld Raman spectrometers equipped with 785 nm diode lasers can be applied successfully for the detection of minerals from the majority of classes of the mineralogical system. For the detection of biomarkers and biomolecules using Raman spectroscopy, e.g. for exobiological applications, the near infrared excitation can be considered as a preferred excitation. Areas of potential applications of the actual instruments include all kind of common geoscience work outdoors. Modified Raman systems can be proposed for studies of superficial or subsurface targets for Mars or Lunar investigations. PMID:21292545

Jehli?ka, Jan; Culka, Adam; Vandenabeele, Peter; Edwards, Howell G M

2011-10-01

215

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

PubMed Central

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

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

2012-01-01

216

Circular dichroism in XUV + IR multiphoton ionization of atoms  

NASA Astrophysics Data System (ADS)

Circular dichroism (CD) is theoretically considered for two-colour multiphoton ionization of arbitrary atomic subshells. In particular, p-subshell ionization is analysed and compared with s-subshell ionization. Simple analytical expressions for the CD are obtained for both s- and p-subshell ionization. The calculations performed for Ne(2p) ionization by an extreme ultraviolet pulse in the presence of an infrared laser pulse show that the CD in this case is appreciably larger than in previously discussed s-shell ionization. It makes this case favourable for applications as a sensitive tool for measuring the helicity of short-wavelength free-electron laser beams.

Kazansky, A. K.; Bozhevolnov, A. V.; Sazhina, I. P.; Kabachnik, N. M.

2014-03-01

217

Ground and excited state infrared spectroscopy of jet-cooled radicals: Exploring the photophysics of trihydronaphthyl and inden-2-ylmethyl.  

PubMed

The alkyl and aromatic CH stretch infrared spectra of inden-2-ylmethyl (I2M, C10H9) and trihydronaphthyl (THN, C10H11) radicals have been recorded under jet-cooled conditions in the ground (D0) and first electronically excited (D1) states using resonant ion-dip infrared (RIDIR) spectroscopy. Previously, the vibronic spectroscopy of a series of C10H9 and C10H11 hydronaphthyl radicals were investigated and their thermochemical properties were evaluated with isomer specificity [J. A. Sebree et al., J. Phys. Chem. A 11, 6255-6262 (2010)]. We show here that one of the m/z 129 spectral carriers characterized in that work was misidentified as 2-hydronaphthyl (2-HN) radical, appearing in a discharge of 1,2-dihydronaphthalene in close proximity to 1-hydronaphthyl radical. The D0-RIDIR spectrum in the alkyl CH stretch region positively identifies the m/z 129 isomer as I2M, whose two-color resonant two-photon ionization (2C-R2PI) spectrum was recently reported by Schmidt and co-workers [T. P. Troy et al., Chem. Sci. 2, 1755-1765 (2011)]. Here, we further characterize the I2M and THN radicals by recording their gas phase IR spectra in the alkyl and aromatic CH stretch regions, and explore the spectroscopic consequences of electronic excitation on the CH stretch absorptions. A local-mode CH stretch Hamiltonian incorporating cubic stretch-bend coupling between anharmonic CH stretches and CH2 scissor modes is utilized to describe their Fermi resonance interactions. Excellent agreement between the experimental and theoretical results facilitates the interpretation of the D0- and D1-state RIDIR spectra of I2M, revealing that upon excitation the alkyl CH stretches decrease in frequency by 70 cm(-1), while the allyl-like CH stretches experience a modest blueshift. In comparison, the photophysics of THN are strikingly different in that the IR transitions that possess vibrational motion along the C?H and C?H bonds are absent in the D1-RIDIR spectrum yet are predicted to be present from the theoretical model. Several hypotheses are considered to account for the perturbations to these vibrations. PMID:24908003

Kidwell, Nathanael M; Mehta-Hurt, Deepali N; Korn, Joseph A; Sibert, Edwin L; Zwier, Timothy S

2014-06-01

218

Zero kinetic energy photoelectron spectroscopy of jet cooled benzo[a]pyrene from resonantly enhanced multiphoton ionization  

NASA Astrophysics Data System (ADS)

We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[a]pyrene (BaP) via resonantly enhanced multiphoton ionization (REMPI). Our analysis concentrates on the vibrational modes of the first excited state (S1) and those of the ground cationic state (D0). Similar to pyrene, another peri-condensed polycyclic aromatic hydrocarbon we have investigated, the first two electronically excited states of BaP exhibit extensive configuration interactions. However, the two electronic states are of the same symmetry, hence vibronic coupling does not introduce any out-of-plane modes in the REMPI spectrum, and Franck-Condon analysis is qualitatively satisfactory. The ZEKE spectra from the in-plane modes observed in the REMPI spectrum demonstrate strong propensity in preserving the vibrational excitation of the intermediate state. Although several additional bands in combination with the vibrational mode of the intermediate state are identifiable, they are much lower in intensity. This observation implies that the molecular structure of BaP has a tremendous capability to accommodate changes in charge density. All observed bands of the cation are IR active, establishing the role of ZEKE spectroscopy in mapping out far infrared bands for astrophysical applications.

Zhang, Jie; Harthcock, Colin; Han, Fangyuan; Kong, Wei

2011-12-01

219

Zero kinetic energy photoelectron spectroscopy of jet cooled benzo[a]pyrene from resonantly enhanced multiphoton ionization.  

PubMed

We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[a]pyrene (BaP) via resonantly enhanced multiphoton ionization (REMPI). Our analysis concentrates on the vibrational modes of the first excited state (S(1)) and those of the ground cationic state (D(0)). Similar to pyrene, another peri-condensed polycyclic aromatic hydrocarbon we have investigated, the first two electronically excited states of BaP exhibit extensive configuration interactions. However, the two electronic states are of the same symmetry, hence vibronic coupling does not introduce any out-of-plane modes in the REMPI spectrum, and Franck-Condon analysis is qualitatively satisfactory. The ZEKE spectra from the in-plane modes observed in the REMPI spectrum demonstrate strong propensity in preserving the vibrational excitation of the intermediate state. Although several additional bands in combination with the vibrational mode of the intermediate state are identifiable, they are much lower in intensity. This observation implies that the molecular structure of BaP has a tremendous capability to accommodate changes in charge density. All observed bands of the cation are IR active, establishing the role of ZEKE spectroscopy in mapping out far infrared bands for astrophysical applications. PMID:22225155

Zhang, Jie; Harthcock, Colin; Han, Fangyuan; Kong, Wei

2011-12-28

220

Nitric oxide releasing materials triggered by near-infrared excitation through tissue filters.  

PubMed

Novel materials for the phototherapeutic release of the bioregulator nitric oxide (nitrogen monoxide) are described. Also reported is a method for scanning these materials with a focused NIR beam to induce photouncaging while minimizing damage from local heating. The new materials consist of poly(dimethylsiloxane) composites with near-infrared-to-visible upconverting nanoparticles (UCNPs) that are cast into a biocompatible polymer disk (PD). These PDs are then impregnated with the photochemical nitric oxide precursor Roussin's black salt (RBS) to give UCNP_RBS_PD devices that generate NO when irradiated with 980 nm light. When the UCNP_RBS_PD composites were irradiated with NIR light through filters composed of porcine tissue, physiologically relevant NO concentrations were released, thus demonstrating the potential of such devices for minimally invasive phototherapeutic applications. PMID:24245494

Burks, Peter T; Garcia, John V; GonzalezIrias, Ricardo; Tillman, Jason T; Niu, Mutong; Mikhailovsky, Alexander A; Zhang, Jinping; Zhang, Fan; Ford, Peter C

2013-12-01

221

Pulsed near-infrared laser diode excitation system for biomedical photoacoustic imaging  

NASA Astrophysics Data System (ADS)

A pulsed laser diode system operating at 905 nm has been developed for the generation of photoacoustic signals in tissue. It was evaluated by measuring the photoacoustic waveforms generated in a blood vessel phantom comprising three dye-filled (?a=1 mm-1) tubes of diameters 120-580 ?m immersed to a maximum depth of 9 mm in a turbid liquid (?'s=1 mm-1). The system was then combined with a cylindrical scanning system to obtain two-dimensional images of a tissue phantom. The signal-to-noise ratio of the detected signals in both cases and the image contrast in the latter suggest that such a system could provide a compact and inexpensive alternative to current excitation sources for superficial imaging applilcations.

Allen, Thomas J.; Beard, Paul C.

2006-12-01

222

EXCITATION OF THE AROMATIC INFRARED EMISSION BANDS: CHEMICAL ENERGY IN HYDROGENATED AMORPHOUS CARBON PARTICLES?  

SciTech Connect

We outline a model for the heating of hydrogenated amorphous carbon (HAC) dust via the release of stored chemical energy and show that this energy ({approx}12 kJ mole{sup -1}) is sufficient to heat dust grains of classical size (50-1000 A) to temperatures at which they can emit at 3.3 {mu}m and other 'UIR' wavelengths. Using laboratory data, we show that this heating process is consistent with a concentration of a few percent of dangling bonds in HAC and may be initiated by the recombination of trapped H atoms. We suggest that the release of chemical energy from dust represents an additional source of excitation for the UIR bands relaxing the previous requirement that only stochastically heated molecules having fewer than {approx}50 atoms can produce emission at 3.3 {mu}m.

Duley, W. W. [Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Williams, D. A., E-mail: wwduley@uwaterloo.ca [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2011-08-20

223

Optical physics enables advances in multiphoton imaging  

Microsoft Academic Search

Since the initial images were taken using a multiphoton imaging technique the method has rapidly established itself as the preferred method for imaging deeply into biological samples with micron resolution in three dimensions. Multiphoton imaging has thus enabled researchers in the life sciences to undertake studies that had previously been believed to be impossible without significantly perturbing the sample. Many

J M Girkin

2003-01-01

224

Multiphoton Entanglement Concentration and Quantum Cryptography  

Microsoft Academic Search

Multiphoton states from parametric down-conversion can be entangled both in polarization and photon number. Maximal high-dimensional entanglement can be concentrated postselectively from these states via photon counting. This makes them natural candidates for quantum key distribution, where the presence of more than one photon per detection interval has up to now been considered undesirable. We propose a simple multiphoton cryptography

Gabriel A. Durkin; Christoph Simon; Dik Bouwmeester

2002-01-01

225

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

226

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

227

Collisional Excitation of Far-infrared Line Emissions from Warm Interstellar Carbon Monoxide (CO)  

NASA Astrophysics Data System (ADS)

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 H2 densities (103-109 cm-3), and presented in the form of rotational diagrams, in which the logarithm of the column density per magnetic substate, log (NJ /gJ ), is plotted for each state, as a function of its energy, EJ . For rotational transitions in the wavelength range accessible to Herschel/PACS, such diagrams are nearly linear when n(H2) >= 108 cm-3. When n(H2) ~ 106.8-108 cm-3, they exhibit significant negative curvature, whereas when n(H2) <= 104.8 cm-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 104-105 cm-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/dTvpropT -b , results have been obtained for H2 densities 103-109 cm-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.

2012-04-01

228

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

229

Correlated multiphoton holes: absence of multiphoton coincidence events.  

PubMed

We generate bipartite states of light which exhibit an absence of multiphoton coincidence events between two modes amid a constant background flux. These "correlated photon holes" are produced by mixing a coherent state and relatively weak spontaneous parametric down-conversion by using a balanced beam splitter. Correlated holes with arbitrarily high photon numbers may be obtained by adjusting the relative phase and amplitude of the inputs. We measure states of up to five photons and verify their nonclassicality. The scheme provides a route for observation of high-photon-number nonclassical correlations without requiring intense quantum resources. PMID:20868159

Afek, I; Ambar, O; Silberberg, Y

2010-08-27

230

Line broadening in multiphoton processes with a resonant intermediate transition  

NASA Technical Reports Server (NTRS)

It is found that the line width of the excitation spectrum for multiphoton ionization is broadened much more severely than the cascade fluorescence originating from the resonant intermediate level. These results derive from the mutual effects of the ionizing and resonating transitions, which are not properly accounted for in perturbative treatments. In general, the ionization line shape can be expressed as the sum of two Lorentzian components, each with different degrees of broadening. This line shape reduces to that of the resonating transition in the limit of vanishing intensities. Moreover, the fluorescence line shape may also exhibit a second component whose amplitude may become important under certain conditions.

Wang, C. C.; James, J. V.; Xia, J.-F.

1983-01-01

231

Fiber-based combined optical coherence and multiphoton microscopy  

NASA Astrophysics Data System (ADS)

This manuscript demonstrates a multimodal imaging system which combined multiphoton microscopy (MPM) imaging modality with Fourier domain (FD) optical coherence microscopy (OCM) imaging modality. The system used a single fiber-based femtosecond laser as the light source for both MPM and OCM modality. The femtosecond fiber laser has a central wavlength of 1.03 ?m, a pulse width of 120 fs and a bandwidth of 29 nm. The systems used fiber-based devices for both MPM and OCM imaging. The MPM and OCM shared the same excitation light path. The excitation light was delivered with the core of a dual-clad fiber. The MPM and OCM signal was collected by different parts of the dual-clad fiber. The MPM signal was collected by the clad of the dual-clad fiber and the OCM signal was collected by the core of the dual-clad fiber. The FD OCM used a home-built InGaAs detector array spectrometer with a maximum Aline speed of 7.7 KHz. The multiphoton signal collection efficiency was analyzed and several imaging modality including second harmonic generation imaging, two-photon excited fluorescence and optical coherent microscopy imaging were demonstrated.

Liu, Gangjun; Chen, Zhongping

2011-02-01

232

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

233

Wavefront sensorless adaptive optics temporal focusing-based multiphoton microscopy  

PubMed Central

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

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

2014-01-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

235

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.

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

236

Time Resolved Infrared Emission from Vibrational Excited Acetylene Following Super Energy Transfer Collisions with Hot Hydrogen  

NASA Astrophysics Data System (ADS)

Can a molecule be activated with large amounts of energy transferred in a single collision between an atom and a molecule? If so, this type of collision will greatly affect molecular reactivity and equilibrium in systems including combustion where abundant hot atoms exist. Conventional expectation of translation to vibration (T-V) energy transfer is that probability decreases exponentially with energy transferred. We show, however, that in collisions between a pair of atom/molecule for which chemical reactions may occur, such as between a hyperthermal H atom and an ambient acetylene molecule, (T-V) energy transfer occurs with surprisingly high efficiency through chemical complex formation. Time-resolved infrared emission observations reveal that collisions between H atoms moving with 60 kcal/mole energy and acetylene molecules result in transfer of up to 70% of this energy into vibrational degrees of freedom. These experimental results are further supported by state of the art quasi-classical trajectory calculations performed by Bowman and coworkers.

Smith, J. M.; Nikow, M.; Dai, J. Ma Andh. L.

2013-06-01

237

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

238

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.

Yew, Elijah; Rowlands, Christopher

2014-01-01

239

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

240

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.

241

Multiphoton Microscopy for Ophthalmic Imaging  

PubMed Central

We review multiphoton microscopy (MPM) including two-photon autofluorescence (2PAF), second harmonic generation (SHG), third harmonic generation (THG), fluorescence lifetime (FLIM), and coherent anti-Stokes Raman Scattering (CARS) with relevance to clinical applications in ophthalmology. The different imaging modalities are discussed highlighting the particular strength that each has for functional tissue imaging. MPM is compared with current clinical ophthalmological imaging techniques such as reflectance confocal microscopy, optical coherence tomography, and fluorescence imaging. In addition, we discuss the future prospects for MPM in disease detection and clinical monitoring of disease progression, understanding fundamental disease mechanisms, and real-time monitoring of drug delivery.

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

2011-01-01

242

High-resolution multiphoton tomography of human skin in vivo and in vitro  

NASA Astrophysics Data System (ADS)

The novel compact femtosecond NIR (near infrared) laser imaging system DermaInspect was used to perform for the first time in vivo high resolution non-invasive 4D tomography of human skin based on multiphoton autofluorescence imaging and second harmonic generation (SHG). Using fast galvoscan mirrors, a time correlated single photon counting (TCSPC) module and femtosecond 80 MHz laser pulses in the spectral range of 750 nm-850 nm human skin was analyzed with subcellular spatial resolution (3D) and 250 ps temporal resolution (4D). The non-linear induced autofluorescence originates from naturally endogenous fluorophores and protein structures like NAD(P)H, flavins, phorphyrins, melanin, elastin and collagen. Collagenous structures were detected using SHG. Tissues of patients with dermatological disorders like nevi and melanoma have been investigated with a clear visualization of cells and intratissue structures. Further characterization of those components was performed by the fluorescence lifetime imaging (FLIM) and the determination of two photon excitation spectra. This method of non invasive high resolution optical biopsy provides a painless diagnostic tool for dermatological applications.

Riemann, Iris; Dimitrov, Enrico; Fischer, Peter; Reif, Annette; Kaatz, Martin; Elsner, Peter; Konig, Karsten

2004-09-01

243

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

244

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

PubMed

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. PMID:23797897

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

2013-01-01

245

Visualizing the mouse podocyte with multiphoton microscopy.  

PubMed

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 (Nphs1(tm1Rkl)/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 Nphs1(tm1Rkl)/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

2012-10-26

246

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.

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

247

Multiphoton microscopy, fluorescence lifetime imaging and optical spectroscopy for the diagnosis of neoplasia  

NASA Astrophysics Data System (ADS)

Cancer morbidity and mortality is greatly reduced when the disease is diagnosed and treated early in its development. Tissue biopsies are the gold standard for cancer diagnosis, and an accurate diagnosis requires a biopsy from the malignant portion of an organ. Light, guided through a fiber optic probe, could be used to inspect regions of interest and provide real-time feedback to determine the optimal tissue site for biopsy. This approach could increase the diagnostic accuracy of current biopsy procedures. The studies in this thesis have characterized changes in tissue optical signals with carcinogenesis, increasing our understanding of the sensitivity of optical techniques for cancer detection. All in vivo studies were conducted on the dimethylbenz[alpha]anthracene treated hamster cheek pouch model of epithelial carcinogenesis. Multiphoton microscopy studies in the near infrared wavelength region quantified changes in tissue morphology and fluorescence with carcinogenesis in vivo. Statistically significant morphological changes with precancer included increased epithelial thickness, loss of stratification in the epithelium, and increased nuclear diameter. Fluorescence changes included a statistically significant decrease in the epithelial fluorescence intensity per voxel at 780 nm excitation, a decrease in the fluorescence lifetime of protein-bound nicotinamide adenine dinucleotide (NADH, an electron donor in oxidative phosphorylation), and an increase in the fluorescence lifetime of protein-bound flavin adenine dinucleotide (FAD, an electron acceptor in oxidative phosphorylation) with precancer. The redox ratio (fluorescence intensity of FAD/NADH, a measure of the cellular oxidation-reduction state) did not significantly change with precancer. Cell culture experiments (MCF10A cells) indicated that the decrease in protein-bound NADH with precancer could be due to increased levels of glycolysis. Point measurements of diffuse reflectance and fluorescence spectra in the ultraviolet to visible wavelength range indicated that the most diagnostic optical signals originate from sub-surface tissue layers. Optical properties extracted from these spectroscopy measurements showed a significant decrease in the hemoglobin saturation, absorption coefficient, reduced scattering coefficient and fluorescence intensity (at 400 nm excitation) in neoplastic compared to normal tissues. The results from these studies indicate that multiphoton microscopy and optical spectroscopy can non-invasively provide information on tissue structure and function in vivo that is related to tissue pathology.

Skala, Melissa Caroline

248

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

249

Picosecond standoff multiphoton detection of gas phase species: initial results  

NASA Astrophysics Data System (ADS)

In the implementation of laser-induced fluorescence (LIF) for the detection of vapor-phase organic compounds that accompany hazardous materials, multiphoton excitation offers a significant advantage over single photon methods. In particular, if the absorption spectra of unwanted background molecules overlap that of the target molecule, single photon LIF is plagued by false positives. Multiphoton methods alleviate this difficulty by requiring that the target molecule be in resonance with multiple molecular transitions. A promising multiphoton method is stimulated Raman adiabatic passage (STIRAP). This method involves a counterintuitive sequence of laser pulses which is capable of transferring 100% of the target molecules to the desired excited state from which fluorescence is to be observed. As a precursor to more complex molecules, we demonstrate the STIRAP technique on sodium vapor using the 3p (2P 1/2) <-- 3s (2S 1/2) and 5s (2S 1/2) <-- 3p (2P 1/2) transitions. This is the first time STIRAP has been achieved on a vapor using picosecond lasers. We produced light to couple the states using two synchronously pumped OPG/OPAs (pumped by the 355 nm light from a picosecond YAG). We measured the fluorescence from the 5s state to both 3p states (2P 1/2, 2P 3/2) and from both 3p states to the 3s state with monochromator using a gated CCD to eliminate Rayleigh scattered light. Our results indicate a four to five-fold increase in the transfer efficiency to the 5s state when the laser pulse that couples the 3p and 5s states precedes the laser pulse tuned to the 3p <-- 3s transition.

Johnson, J. Bruce; Lyon, Kevin; Murry, William D.; Britton, Daniel R.; Johnson, Michael J.

2008-05-01

250

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

251

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

252

Multiphoton analysis of normal and diseased livers  

NASA Astrophysics Data System (ADS)

Diseases associated with the liver, a major internal organ, can lead to serious health problems. In this work, we present multiphoton images of normal and diseased liver specimens and we will characterize the changes to pathological liver specimens. In particular, we will focus on the physiological changes associated with liver fibrosis. Our results show that multiphoton microscopy is a useful technique for distinguishing normal and diseased liver tissues and that it has potential applications for in vivo diagnosis of liver diseases.

Liu, Yuan; Fwu, Peter T.; Chen, Hsiao-Ching; Chiou, Ling-Ling; Huang, Guan-Tarn; Lo, Wen; Lee, Hsuan-Shu; Dong, Chen-Yuan

2005-03-01

253

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

254

DNA Multiphoton Absorption Generates Localized Damage for Studying Repair Dynamics in Live Cells  

PubMed Central

Investigations into the spatiotemporal dynamics of DNA repair using live-cell imaging are aided by the ability to generate well defined regions of ultravioletlike photolesions in an optical microscope. We demonstrate that multiphoton excitation of DNA in live cells with visible femtosecond pulses produces thymine cyclopyrimidine dimers (CPDs), the primary ultraviolet DNA photoproduct. The CPDs are produced with a cubic to supercubic power dependence using pulses in the wavelength range from at least 400 to 525 nm. We show that the CPDs are confined in all three spatial dimensions, making multiphoton excitation of DNA with visible light an ideal technique for generating localized DNA photolesions in a wide variety of samples, from cultured cells to thicker tissues. We demonstrate the utility of this method by applying it to investigate the spatiotemporal recruitment of GFP-tagged topoisomerase I (TopI) to sites of localized DNA damage in polytene chromosomes within live cells of optically thick Drosophila salivary glands.

Daddysman, Matthew K.; Fecko, Christopher J.

2011-01-01

255

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.

256

Multiphoton microscopy as a diagnostic imaging modality for lung cancer  

NASA Astrophysics Data System (ADS)

Lung cancer is the leading killer among all cancers for both men and women in the US, and is associated with one of the lowest 5-year survival rates. Current diagnostic techniques, such as histopathological assessment of tissue obtained by computed tomography guided biopsies, have limited accuracy, especially for small lesions. Early diagnosis of lung cancer can be improved by introducing a real-time, optical guidance method based on the in vivo application of multiphoton microscopy (MPM). In particular, we hypothesize that MPM imaging of living lung tissue based on twophoton excited intrinsic fluorescence and second harmonic generation can provide sufficient morphologic and spectroscopic information to distinguish between normal and diseased lung tissue. Here, we used an experimental approach based on MPM with multichannel fluorescence detection for initial discovery that MPM spectral imaging could differentiate between normal and neoplastic lung in ex vivo samples from a murine model of lung cancer. Current results indicate that MPM imaging can directly distinguish normal and neoplastic lung tissues based on their distinct morphologies and fluorescence emission properties in non-processed lung tissue. Moreover, we found initial indication that MPM imaging differentiates between normal alveolar tissue, inflammatory foci, and lung neoplasms. Our long-term goal is to apply results from ex vivo lung specimens to aid in the development of multiphoton endoscopy for in vivo imaging of lung abnormalities in various animal models, and ultimately for the diagnosis of human lung cancer.

Pavlova, Ina; Hume, Kelly R.; Yazinski, Stephanie A.; Peters, Rachel M.; Weiss, Robert S.; Webb, Watt W.

2010-02-01

257

Multiphoton imaging of the dentine-enamel junction.  

PubMed

Multiphoton microscopy has been used to reveal structural details of dentine and enamel at the dentin-enamel junction (DEJ) based on their 2-photon excited fluorescence (2PEF) emission and second harmonic generation (SHG). In dentine tubule 2PEF intensity varies due to protein content variation. Intertubular dentin produces both SHG and 2PEF signals. Tubules are surrounded by a thin circular zone with a lower SHG signal than the bulk dentine and the presence of collagen fibers perpendicular to the tubule longitudinal axis is indicated by strong SHG responses. The DEJ appears as a low intensity line on the 2PEF images and this was never previously reported. The SHG signal is completely absent for enamel and aprismatic enamel shows a homogeneous low 2PEF signal contrary to prismatic enamel. The SHG intensity of mantle dentine is increasing from the dentine-enamel junction in the first 12 ?m indicating a progressive presence of fibrillar collagen and corresponding to the more external part of mantle dentine where matrix metallo-proteases accumulate. The high information content of multiphoton images confirms the huge potential of this method to investigate tooth structures in physiological and pathological conditions. PMID:22815209

Cloitre, Thierry; Panayotov, Ivan V; Tassery, Hervé; Gergely, Csilla; Levallois, Bernard; Cuisinier, Frédéric J G

2013-04-01

258

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

SciTech Connect

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

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

1982-01-01

259

Multiphoton ionization of liquid water with 3.0-5.0 eV photons  

Microsoft Academic Search

We report a picosecond laser study of the transient absorption of hydrated electrons generated by 3-5 eV multiphoton ionization of liquid water. The geminate kinetics indicate that e{sub aq}⁻ is produced by at least three different mechanisms over this energy range. Power dependence of the signal amplitude shows a two-photon threshold for 4.0 eV excitation and a three-photon threshold absorption

Robert A. Crowell; David M. Bartels

1996-01-01

260

Multiphoton ionization of cesium through resonant dissociative states of Cs2  

Microsoft Academic Search

The multiphoton excitation of cesium through potentially resonant continuum molecular states is investigated over the 6200-5000-Å wavelength region with a tunable dye-laser source having a 0.06-0.08-Å linewidth and a space-charge ionization detector sensitive to a few ions per second. Conditions are established under which the lifetime of the resonant intermediate state against photoexcitation exceeds the lifetime against dissociation. Single- and

C. B. Collins; B. W. Johnson; M. Y. Mirza; D. Popescu; Iovitzu Popescu

1974-01-01

261

Water assisted multi-photon ionization of N 2 by KrF lasers  

Microsoft Academic Search

Effects of water vapor on multiphoton ionization of N2 by a narrowband tunable KrF laser were compared to ionization of dry N2. In dry N2, ionization is non-resonant and requires 3 + 1 photon absorptions. In the presence of water, ionization is through a resonant two-photon excitation of H2O, followed by collisional energy exchange with N2 molecules and two single-photon

Gabriel Laufer; Anthony S. Lee

1997-01-01

262

Two-color multiphoton ionization of diazabicyclooctane in a supersonic free jet  

NASA Astrophysics Data System (ADS)

Two-color multiphoton ionization (MPI) spectroscopy has been applied for diazabicyclooctane (DABCO) in a supersonic free jet. The MPI spectra due to transitions from the various vibronic levels of the S 1 (3s Rydberg) state which were excited by the first laser revealed the high Rydberg states above the adiabatic ionization potential. The ionization process and the vibrational potential of the ion are discussed.

Fujii, Masaaki; Ebata, Takayuki; Mikami, Naohiko; Ito, Mitsuo

1983-11-01

263

Two colour multiphoton ionization spectroscopy of uranium from a metastable state  

NASA Astrophysics Data System (ADS)

Using two pulsed tunable dye lasers, a two colour multiphoton ionization process has been utilised to explore the higher energy levels of uranium. One hundred and thirty eight new UI levels have been observed in the 37540 38420 cm-1 region. J assignments of these levels have been suggested on the basis of their excitation from intermediate levels with known and contiguous J values. In eight cases the J assignments are unique.

Bajaj, P. N.; Manohar, K. G.; Suri, B. M.; Dasgupta, K.; Talukdar, R.; Chakraborti, P. K.; Rao, P. R. K.

1988-09-01

264

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

265

Optical biopsy in high-speed handheld miniaturized multifocal multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Histological analysis is the clinical standard for assessing tissue health and the identification of pathological states. Its invasive nature dictates that its use should be minimized without compromising diagnostic accuracy. A promising method for minimally invasive histological analysis is optical biopsy, which provides cross sectional or 3D images without any physical sectionings. Optical biopsy method based on multiphoton excitation microscopy can image cross-sectional image for deep tissue structures with subcellular resolution based on tissue endogenous fluorescence molecules. Despite its suitability for tissue imaging, multiphoton microscopy has not been used for in vivo clinical applications due to both compactness and imaging speed problems. We are developing a high-speed, handheld, miniaturized multifocal multiphoton microscope (H2M4) as an optical biopsy probe to enable optical biopsy with subcellular resolution. We incorporate a compact raster scanning actuator based on optimizing a piezo-driven tip tilt mirror by increasing its bandwidth, and reducing its nonlinearity. For flexible light delivery, we choose a photonic bandgap crystal fiber, which transmits ultrashort pulsed laser delivery with reduced spectral distortion and pulse width broadening. We further demonstrate that this fiber produces minimal spatial mode distortion and can achieve comparable image point spread function (PSF) as free space delivery. We further investigate the applicability of multiphoton microscopy for clinical dermal investigation by imaging ex vivo human skins with both normal and abnormal physiologies. This demonstrates the performance of H2M4 and the possibility of optical biopsy for diagnosing skin diseases.

Kim, Daekeun; Kim, Ki Hean; Yazdanfar, Siavash; So, Peter T. C.

2005-03-01

266

Characterization and application of chirped photonic crystal fiber in multiphoton imaging.  

PubMed

Fiber delivery of ultrashort pulses is important for multiphoton endoscopy. A chirped photonic crystal fiber (CPCF) is first characterized for its transmission bandwidth, propagation loss, and dispersion properties. Its extremely low dispersion (~150?fs2/m) enables the delivery of sub-30 fs pulses through a ~1 m-long CPCF. The CPCF is then incorporated into a multiphoton imaging system and its performance is demonstrated by imaging various biological samples including yew leaf, mouse tendon, and human skin. The imaging quality is further compared with images acquired by a multiphoton imaging system with free-space or hollow-core photonic band-gap fiber (PBF) delivery of pulses. Compared with free-space system, the CPCF delivered system maintains the same ultrashort pulsewidth and the image qualities are comparable. Compared with the PBF delivery, CPCF provides a 35 times shorter pulsewidth at the sample location, which results in a ~12 and 50 times improvement in two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG) signals respectively. Our results show that CPCF has great potential for fiber delivery of ultrashort pulses for multiphoton endoscopy. PMID:24921739

Yu, Jiali; Zeng, Haishan; Lui, Harvey; Skibina, Julia S; Steinmeyer, Günter; Tang, Shuo

2014-05-01

267

Multi-photon laser scanning microscopy using an acoustic optical deflector.  

PubMed

Multi-photon laser scanning microscopes have many advantages over single-photon systems. However, the speed and flexibility of currently available multi-photon microscopes are limited by the use of mechanical mirrors to steer pulsed radiation for fluorophore excitation. Here, we describe the multi-photon adaptation of a confocal microscope that uses an acoustic optical deflector (AOD) for beam steering. AODs are capable of very rapid scanning and, in addition, offer the flexibility of zooming, panning, and being adjustable for slow image acquisition. Because of the highly dispersive nature of AODs, pulsed radiation must be temporally compressed by introducing negative dispersion into the beam path. More critically, pulsed radiation must also be spatially compressed by introducing lateral dispersion into the beam path. This was accomplished by using two prisms in the external beam path and by introducing a third prism element subsequent to the AOD. The end result is an AOD-based multi-photon microscope that is capable of rapid imaging of physiological events as well as slow detection of weakly fluorescent biological samples. PMID:12324446

Lechleiter, James D; Lin, Da-Ting; Sieneart, Ilse

2002-10-01

268

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

269

The Excitation and Metallicity of Galactic H II Regions from Infrared Space Observatory SWS Observations of Mid-Infrared Fine-Structure Lines  

Microsoft Academic Search

We present mid-infrared Infrared Space Observatory Short-Wavelength Spectrometer (ISO-SWS) observations of the fine-structure emissions lines [Ne II] 12.8 mum, [Ne III] 15.6 mum, [Ne III] 36.0 mum, [Ar II] 6.99 mum, [Ar III] 8.99 mum, [S III] 18.7 mum, [S III] 33.5 mum, and [S IV] 10.5 mum and the recombination lines Bralpha and Brbeta in a sample of 112

Uriel Giveon; Amiel Sternberg; Dieter Lutz; Helmut Feuchtgruber; A. W. A. Pauldrach

2002-01-01

270

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

271

Ultraviolet and infrared photon-excited synergistic effect in Er3+-doped YbF3 phosphors.  

PubMed

A synergistic effect between UV down-conversion and IR up-conversion is witnessed in YbF3:Er3+ phosphors by employing the dual wavelength (369 nm and 980 nm) excitation source. The synergistic effect originates from an abnormal energy transfer between Er3+ ions, in which the Er3+ ions in metastable states excited by 369 nm photons are excited again by the 980 nm IR photons. The dual wavelength excited red emission intensity is 1.1 times the total red emission intensities from 369 nm and 980 nm single excitation. The synergistic effect refers us to a way to convert both high-energy and low-energy photons into one middle-energy photon with high quantum yield. PMID:22089561

Wang, Xiangfu; Yan, Xiaohong

2011-11-15

272

Eliminating the scattering ambiguity in multifocal, multimodal, multiphoton imaging systems.  

PubMed

In this work we present how to entirely remove the scattering ambiguity present in existing multiphoton multifocal systems. This is achieved through the development and implementation of single-element detection systems that incorporate high-speed photon-counting electronics. These systems can be used to image entire volumes in the time it takes to perform a single transverse scan (four depths simultaneously at a rate of 30 Hz). In addition, this capability is further exploited to accomplish single-element detection of multiple modalities (two photon excited fluorescence and second harmonic generation) and to perform efficient image deconvolution. Finally, we demonstrate a new system that promises to significantly simplify this promising technology. PMID:22461190

Hoover, Erich E; Field, Jeffrey J; Winters, David G; Young, Michael D; Chandler, Eric V; Speirs, John C; Lapenna, Jacob T; Kim, Susy M; Ding, Shi-You; Bartels, Randy A; Wang, Jing W; Squier, Jeff A

2012-05-01

273

Multiphoton spectroscopy of polymers for all-optical switching  

NASA Astrophysics Data System (ADS)

We present nonlinear optical spectroscopy of the model conjugated polymer MEH-PPV, a derivative of poly(paraphenylenevinylene) (PPV) and compare it with PPV. We perform multiphoton excited fluorescence spectroscopy and z-scan studies of solutions compared with third-harmonic generation, linear and nonlinear waveguide spectroscopy with intensity dependent prism coupling of thin films in the NIR region. Spectra of the nonlinear absorption coefficient and nonlinear refractive index are used to identify the figures of merit (FOM). We observe a spectral window at 1100 - 1200 nm were the application demands for all-optical waveguide switching are fulfilled. We demonstrate all-optical refractive index changes in the order of 0.001. Control of the molecular weight of MEH-PPVs enables improved film forming properties, reduced birefringence and ultimately low waveguide propagation losses < 1 dB/cm.

Bahtiar, Ayi; Koynov, Kaloian; Kibrom, Asmorom; Ahn, Taek; Bubeck, Christoph

2006-09-01

274

New developments in multimodal clinical multiphoton tomography  

NASA Astrophysics Data System (ADS)

80 years ago, the PhD student Maria Goeppert predicted in her thesis in Goettingen, Germany, two-photon effects. It took 30 years to prove her theory, and another three decades to realize the first two-photon microscope. With the beginning of this millennium, first clinical multiphoton tomographs started operation in research institutions, hospitals, and in the cosmetic industry. The multiphoton tomograph MPTflexTM with its miniaturized flexible scan head became the Prism-Award 2010 winner in the category Life Sciences. Multiphoton tomographs with its superior submicron spatial resolution can be upgraded to 5D imaging tools by adding spectral time-correlated single photon counting units. Furthermore, multimodal hybrid tomographs provide chemical fingerprinting and fast wide-field imaging. The world's first clinical CARS studies have been performed with a hybrid multimodal multiphoton tomograph in spring 2010. In particular, nonfluorescent lipids and water as well as mitochondrial fluorescent NAD(P)H, fluorescent elastin, keratin, and melanin as well as SHG-active collagen have been imaged in patients with dermatological disorders. Further multimodal approaches include the combination of multiphoton tomographs with low-resolution imaging tools such as ultrasound, optoacoustic, 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 (malignant melanoma), optimization of treatment strategies (wound healing, dermatitis), and cosmetic research including long-term biosafety tests of ZnO sunscreen nanoparticles and the measurement of the stimulated biosynthesis of collagen by anti-ageing products.

König, Karsten

2011-02-01

275

Human bladder cancer diagnosis using multiphoton microscopy  

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

276

Human bladder cancer diagnosis using Multiphoton microscopy.  

PubMed

At the time of diagnosis, approximately 75% of bladder cancers are non-muscle invasive. Appropriate diagnosis and surgical resection at this stage improves prognosis dramatically. However, these lesions, being small and/or flat, are often missed by conventional white-light cystoscopes. Furthermore, it is difficult to assess the surgical margin for negativity using conventional cystoscopes. Resultantly, the recurrence rates in patients with early bladder cancer are very high. This is currently addressed by repeat cystoscopies and biopsies, which can last throughout the life of a patient, increasing cost and patient morbidity. Multiphoton endoscopes offer a potential solution, allowing real time, non-invasive biopsies of the human bladder, as well as an up-close assessment of the resection margin. While miniaturization of the Multiphoton microscope into an endoscopic format is currently in progress, we present results here indicating that Multiphoton imaging (using a bench-top Multiphoton microscope) can indeed identify cancers in fresh, unfixed human bladder biopsies. Multiphoton images are acquired in two channels: (1) broadband autofluorescence from cells, and (2) second harmonic generation (SHG), mostly by tissue collagen. These images are then compared with gold standard hematoxylin/eosin (H&E) stained histopathology slides from the same specimen. Based on a "training set" and a very small "blinded set" of samples, we have found excellent correlation between the Multiphoton and histopathological diagnoses. A larger blinded analysis by two independent uropathologists is currently in progress. We expect that the conclusion of this phase will provide us with diagnostic accuracy estimates, as well as the degree of inter-observer heterogeneity. PMID:19360140

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

2009-01-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

278

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

279

Multiphoton coherent control in complex systems  

PubMed Central

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

Goswami, Debabrata

2005-01-01

280

Multiphoton polymerization using optical trap assisted nanopatterning  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

281

Multiphoton spectroscopy of a hybrid quantum system  

NASA Astrophysics Data System (ADS)

We report on experimental multiphoton spectroscopy of a hybrid quantum system consisting of a superconducting phase qubit coherently coupled to an intrinsic two-level system (TLS). We directly probe hybridized states of the combined qubit-TLS system in the strongly interacting regime, where both the qubit-TLS coupling and the driving cannot be considered as weak perturbations. This regime is described by a theoretical model which incorporates anharmonic corrections, multiphoton processes and decoherence. We present a detailed comparison between experiment and theory and find excellent agreement over a wide range of parameters.

Bushev, P.; Müller, C.; Lisenfeld, J.; Cole, J. H.; Lukashenko, A.; Shnirman, A.; Ustinov, A. V.

2010-10-01

282

Excited state structure of 4-(dimethylamino)benzonitrile studied by femtosecond mid-infrared spectroscopy and ab initio calculations  

Microsoft Academic Search

Combining femtosecond transient vibrational spectroscopy and high-level calculations is a powerful tool in the determination of excited-state structures. Striking differences in the experimental vibrational pattern of the locally excited states of 4-(dimethylamino)benzonitrile (DMABN) and 4-aminobenzonitrile (ABN) are explained on the basis of molecular structures obtained from ab initio complete-active-space self-consistent-field (CASSCF) calculations, giving evidence for a strong sensitivity of the

C. Chudoba; A. Kummrow; J. Dreyer; J. Stenger; E. T. J. Nibbering; T. Elsaesser; K. A. Zachariasse

1999-01-01

283

Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of benzo[e]pyrene  

NASA Astrophysics Data System (ADS)

We report zero kinetic energy (ZEKE) photoelectron spectroscopy via resonantly enhanced multiphoton ionization (REMPI) for benzo[e]pyrene. Extensive vibronic coupling between the first electronically excited state and a nearby state allows b2 modes to be observed which would be Franck-Condon (FC) disallowed. These vibronic modes are comparable in intensity to the FC allowed a1 modes. We are able to qualitatively simulate the vibronic spectra of both REMPI and ZEKE using density functional methods. The ZEKE spectra demonstrate propensity in preserving the vibrational excitation of the intermediate state. These results suggest a remarkable structural stability of BeP in accommodating the additional charge.

Harthcock, Colin; Zhang, Jie; Kong, Wei

2013-01-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

285

Activatable organic near-infrared fluorescent probes based on a bacteriochlorin platform: synthesis and multicolor in vivo imaging with a single excitation.  

PubMed

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

Harada, Toshiko; Sano, Kohei; Sato, Kazuhide; Watanabe, Rira; Yu, Zhanqian; Hanaoka, Hirofumi; Nakajima, Takahito; Choyke, Peter L; Ptaszek, Marcin; Kobayashi, Hisataka

2014-02-19

286

Fast multiphoton microfabrication of freeform polymer microstructures by spatiotemporal focusing and patterned generation  

NASA Astrophysics Data System (ADS)

One of the limits of a conventional multiphoton microfabrication is its low throughput due to the sequential nature of scanning process. In this study, a multiphoton microfabrication system based on spatiotemporal focusing and patterned excitation has been developed to provide freeform polymer microstructures fast. The system integrates a 10 kHz repetition rate ultrafast amplifier featuring strong instantanrror device generating designed patterns at the focal plane. As the result, three-dimensional freeform polymer microstructures using Rose Bengal as the photoinitiator are created by sequentially stacking up two-dimensional (2D) structures layer-by-layer. The size of each 2D fabrication area can be larger than 100 × 100 ?m2. Compared with scanning process or fixed mask pattern generation, this approach provides two- or three-fold fabrication speed and freeform microstructures. Furthermore, the system is capable of optical sectioning the fabricated microstructures for providing 3D inspection.

Li, Y.-C.; Cheng, L.-C.; Lien, C.-H.; Chang, C.-Y.; Yen, W.-C.; Chen, S.-J.

2012-10-01

287

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

NASA Technical Reports Server (NTRS)

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 the IR spectra contain between 20 and 40 C atoms. The results are compared with results from a thermal approximation. It is found that, for high levels of vibrational excitation and emission from low-frequency modes, the two methods produce similar results. Also, consideration is given to the relationship between PAH molecules and amorphous C particles, the most likely interstellar PAH molecular structures, the spectroscopic structure produced by PAHs and PAH-related materials in the UV portion of the interstellar extinction curve, and the influence of PAH charge on the UV, visible, and IR regions.

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

1989-01-01

288

Autoionization of H2 Induced by a Doubly Excited Triplet State.  

National Technical Information Service (NTIS)

The photoionization of molecular hydrogen has been extensively studied in recent years. For the singlet states, a variety of schemes for multiphoton excitation from the ground state has been developed. The spectroscopy of the triplet states usually starts...

N. Bjerre S. R. Keiding L. J. Lembo H. Helm

1988-01-01

289

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

290

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

SciTech Connect

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

Johnson, P.M.

1991-10-01

291

Fundamental infrared lattice vibration spectrum and the laser-excited Raman spectrum of MoSe2  

Microsoft Academic Search

The absorption spectrum of a single crystal of MoSe2, in the region of the fundamental transverse optic vibration frequency is reported. A damped oscillator fit to the fundamental band gives the transverse optical frequency ? = 283 cm. The IR active fundamental transverse optic vibration frequency also appears in the laser-excited Raman spectrum of MoSe2, crystal.

O. P. Agnihotri; H. K. Sehgal

1972-01-01

292

State-selective vibrational excitation and dissociation of H2+ by strong infrared laser pulses: below-resonant versus resonant laser fields and electron-field following.  

PubMed

The quantum dynamics of vibrational excitation and dissociation of H(2)(+) by strong and temporally shaped infrared (IR) laser pulses has been studied on the femtosecond (fs) time scale by numerical solution of the time-dependent Schrödinger equation with explicit treatment of nuclear and electron motion beyond the Born-Oppenheimer approximation. Using sin(2)-shaped laser pulses of 120 fs duration with a peak intensity of I(0) > 10(14) W/cm(2), it has been found that below-resonant vibrational excitation with a laser carrier frequency of ? < ?(10)/2 (where ?(10) is the frequency of the |v = 0> ? |v = 1> vibrational transition) is much more efficient than a quasi-resonant vibrational excitation at ? ? ?(10). In particular, at the below-resonant laser carrier frequency ? = 0.3641 × 10(-2) au (799.17 cm(-1)), dissociation probabilities of H(2)(+) (15.3% at the end of the 120 fs laser pulse and 21% at t = 240 fs) are more than 3 orders of magnitude higher than those obtained for the quasi-resonant laser frequency ? = 1.013 × 10(-2) au (2223.72 cm(-1)). Probabilities of state-selective population transfer to vibrational states |v = 1>, |v = 2>, and |v = 3> from the vibrational ground state |v = 0> of about 85% have been calculated in the optimal below-resonant cases. The underlying mechanism of the efficient below-resonant vibrational excitation is the electron-field following and simultaneous transfer of energy to the nuclear coordinate. PMID:22916791

Paramonov, Guennaddi K; Kühn, Oliver

2012-11-26

293

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

2014-05-01

294

Mixed quantum-classical molecular dynamics study of the hydroxyl stretch in methanol/carbon-tetrachloride mixtures II: excited state hydrogen bonding structure and dynamics, infrared emission spectrum, and excited state lifetime.  

PubMed

We present a mixed quantum-classical molecular dynamics study of the hydrogen-bonding structure and dynamics of a vibrationally excited hydroxyl stretch in methanol/carbon-tetrachloride mixtures. The adiabatic Hamiltonian of the quantum-mechanical hydroxyl is diagonalized on-the-fly to obtain the ground and first-excited adiabatic energy levels and wave functions which depend parametrically on the instantaneous configuration of the classical degrees of freedom. The dynamics of the classical degrees of freedom are determined by Hellmann-Feynman forces obtained by taking the expectation value of the force with respect to the ground or excited vibrational wave functions. Polarizable force fields are used which were previously shown to reproduce the experimental infrared absorption spectrum rather well, for different isotopomers and over a wide composition range [Kwac, K.; Geva, E. J. Phys. Chem. B 2011, 115, 9184]. We show that the agreement of the absorption spectra with experiment can be further improved by accounting for the dependence of the dipole moment derivatives on the configuration of the classical degrees of freedom. We find that the propensity of a methanol molecule to form hydrogen bonds increases upon photoexcitation of its hydroxyl stretch, thereby leading to a sizable red-shift of the corresponding emission spectrum relative to the absorption spectrum. Treating the relaxation from the first excited to the ground state as a nonadiabatic process, and calculating its rate within the framework of Fermi's golden rule and the harmonic-Schofield quantum correction factor, we were able to predict a lifetime which is of the same order of magnitude as the experimental value. The experimental dependence of the lifetime on the transition frequency is also reproduced. Nonlinear mapping relations between the hydroxyl transition frequency and bond length in the excited state and the electric field along the hydroxyl bond axis are established. These mapping relations make it possible to reduce the computational cost of the mixed quantum-classical treatment to that of a fully classical treatment. PMID:22283660

Kwac, Kijeong; Geva, Eitan

2012-03-01

295

Simultaneous excitation of multiple fluororophores with a compact femtosecond laser  

Microsoft Academic Search

We report on a flexible multiphoton imaging system, suitable for simultaneous and efficient excitation of red (DsRed), yellow (YFP), green (GFP) and blue (DAPI) fluorophores. We used a simple, compact laser system, consisting of a 1 mum high energy diode-pumped oscillator and a tunable wavelength extension using a photonics crystal fibre. The combination of a near IR excitation wavelength, high

Philippe Legros; Daniel Choquet; Stéphane Gueguen; Eric Mottay; Nelly Deguil

2006-01-01

296

Elementary excitations in narrow-gap semiconductors by picosecond infrared pulses. Final report 1 Jan 77-31 Dec 81  

SciTech Connect

In this grant research, we have demonstrated efficient switching of high-power carbon dioxide laser radiation at picosecond speeds in the narrow-gap semiconductors indium antimonide, lead telluride, and mercury cadmium telluride. Excitation from a modelocked Nd: glass laser has been used to generate pulses of 10 micrometer radiation of approximately 2psec in duration by a dense transient electron-hole gas in these materials. This work takes advantage of the unique material properties of the narrow-gap semiconductors.

Nurmikko, A.V.

1981-02-23

297

Multiphoton Imaging of Renal Regulatory Mechanisms  

NSDL National Science Digital Library

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

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

2009-04-01

298

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.

2008-03-01

299

Multi-photon optical rotation by molecules  

NASA Astrophysics Data System (ADS)

Forward scattering of polarized light by a chiral molecule results in optical rotation. Ordinary optical rotation, a single-photon effect, is independent of intensity, I. Multi-photon optical rotation is proportional to I^N-1, where N is the number of photons involved the scattering event. The ordinary optical rotation changes with temperature, and so the absorption of light can also cause an intensity-dependent change in optical rotation. We used a polarimeter to measure the change in optical rotation with light intensity for several molecules in solution: sucrose, borneol, uridine and phenylalanine. Making use of Faraday rotation, we added a time-dependent rotation of the light to our apparatus. This allowed us to use Fourier analysis to separate the multi-photon optical rotation from the temperature change in ordinary optical rotation and improved the signal-to-noise.

Cameron, R.; Tabisz, G. C.

2001-05-01

300

New Directions in 3-D Multiphoton Lithography  

Microsoft Academic Search

Multiphoton absorption polymerization (MAP) is a promising technique for the lithographic fabrication of 3-D microdevices. However, this technique also has two major shortcomings that have so far precluded its use in the mass production of devices. First, MAP is an inherently serial technique, and structures must be created on a voxel-by-voxel basis. Second, the fabrication of many desirable 3-D devices

John Fourkas; Christopher Lafratta; Richard Farrer; Linjie Li; Michael Naughton

2006-01-01

301

Fundamental studies of molecular multiphoton ionization  

SciTech Connect

For several years the authors have performed fundamental studies of molecular multiphoton ionization (MPI). We will present a potpourri of techniques and results chosen to illustrate the interesting complexities of molecular MPI. Techniques used include time-of-flight mass spectroscopy, photoelectron spectroscopy, supersonic expansion cooling of molecular beams, harmonic generation, two-color laser MPI, and polarization spectroscopy. Whenever possible the relevance of these results to resonance ionization spectroscopy schemes will be delineated. 23 references, 10 figures.

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

1984-04-01

302

In vivo confocal and multiphoton microendoscopy  

PubMed Central

The ability to conduct high-resolution fluorescence imaging in internal organs of small animal models in situ and over time can make a significant impact in biomedical research. Toward this goal, we developed a real-time confocal and multiphoton endoscopic imaging system. Using 1-mm-diameter endoscopes based on gradient index lenses, we demonstrate video-rate multicolor multimodal imaging with cellular resolution in live mice.

Kim, Pilhan; Puoris'haag, Mehron; Cote, Daniel; Lin, Charles P.; Yun, Seok H.

2009-01-01

303

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

304

Focal switching of photochromic fluorescent proteins enables multiphoton microscopy with superior image contrast  

PubMed Central

Probing biological structures and functions deep inside live organisms with light is highly desirable. Among the current optical imaging modalities, multiphoton fluorescence microscopy exhibits the best contrast for imaging scattering samples by employing a spatially confined nonlinear excitation. However, as the incident laser power drops exponentially with imaging depth into the sample due to the scattering loss, the out-of-focus background eventually overwhelms the in-focus signal, which defines a fundamental imaging-depth limit. Herein we significantly improve the image contrast for deep scattering samples by harnessing reversibly switchable fluorescent proteins (RSFPs) which can be cycled between bright and dark states upon light illumination. Two distinct techniques, multiphoton deactivation and imaging (MPDI) and multiphoton activation and imaging (MPAI), are demonstrated on tissue phantoms labeled with Dronpa protein. Such a focal switch approach can generate pseudo background-free images. Conceptually different from wave-based approaches that try to reduce light scattering in turbid samples, our work represents a molecule-based strategy that focused on imaging probes.

Kao, Ya-Ting; Zhu, Xinxin; Xu, Fang; Min, Wei

2012-01-01

305

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

306

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

PubMed

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

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

2014-07-22

307

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

NASA Astrophysics Data System (ADS)

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

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

1996-01-01

308

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

309

Discrimination of zeolites and beryllium containing silicates using portable Raman spectroscometric equipment with near-infrared excitation.  

PubMed

In this paper Raman spectra were obtained for a series of zeolites (thomsonite, stilbite, natrolite) and beryllium containing silicates (beryl, chrysoberyl, euclase, phenacite, bavenite, milarite) using a portable Raman specrometer with a 785 nm laser excitation to show the possibility to apply this setting for unambiguous detection and discrimination of these silicate minerals. Obtained spectra contain the most intense Raman bands at the same positions ±2-4 cm(-1) as reported in the literature. The use of these bands permits the unambiguous identification of these phases. Data show the possibility to discriminate individual species of similar whitish color and aspect. Measurements showed an excellent correspondence of Raman bands obtained using the portable system and a laboratory Raman microspectrometer (with the same excitation laser wavelenght). However, for several minerals of these groups (chrysoberyl, bertrandite, chiavennite) Raman spectra were not of sufficient quality to permit unambiguous identification. The reasons are discussed. Raman spectrum of chiavennite CaMnBe(2)Si(5)O(13)(OH)(2)·2(H(2)O) - a transformation product occurring together with bavenite on the surface of beryl crystals was obtained for the first time using the laboratory Raman spectrometer. PMID:22099060

Jehli?ka, J; Vandenabeele, P; Edwards, H G M

2012-02-01

310

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

311

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

312

Near-field multiphoton nanolithography using an apertureless optical probe  

Microsoft Academic Search

Near-field multiphoton optical lithography is demonstrated by using ~120 fs laser pulses at 790 nm in an apertureless near-field optical microscope, which produce the lithographic features with ~ 70 nm resolution. The technique takes advantage of the field enhancement at the extremity of a metallic probe to induce nanoscale multiphoton absorption and polymerization in a commercial photoresist, SU-8. Even without

Xiaobo Yin; Nicholas Fang; Xiang Zhang; Ignacio B. Martini; Benjamin J. Schwartz

2003-01-01

313

Bimolecular reactions and energy-transfer processes of highly vibrationally excited molecules related to energetic materials  

NASA Astrophysics Data System (ADS)

Infrared Multiphoton Absorption (IRMPA) was used to produce populations of vibrationally excited 1,1,2-trifluoroethane, which were characterized by optoacoustic measurements of absorbed laser power and collision free decomposition yields. The measurements were accurately fitted with a Master Equation that included Quack's theory of IRMPA, three RKM unimolecular reaction channels, and collisional energy transfer. The highly constrained adjustable parameters indicate that the optical coupling matrix elements are dramatically reduced in magnitude near reaction threshold energies where vibrational anharmonicity becomes important. Observed infrared fluorescence from the excited molecules is in excellent agreement with Master Equation predictions and it was used to monitor collisional deactivation of the excited molecules. The energy transfer exhibits a weak vibrational energy on bimolecular reactions of 1,1 2-trifluorethane (TFE), but no such effects have yet been observed. A Monte Carlo method is described for efficient multidimensional integration not restricted to hyper-dimensional rectangles, but applied to more complicated domains. When known, the boundaries of a arbitrary integration region can be used to define the sampling domain, resulting in sampling with unit efficiency.

Barker, John R.

1987-12-01

314

Photon absorption in step-wise multi-photon activation fluorescence (SMPAF) of Sepia melanin  

NASA Astrophysics Data System (ADS)

Previous research has shown that melanin goes through a step-wise three-photon absorption process when the fluorescence is activated with high laser intensity. We have conducted further research using even higher laser intensity for the activation, and have shown the possibility of observing power dependence other than third-order. This article discusses the possible energy states of Sepia melanin by studying the power dependence curves of the step-wise multi-photon activated fluorescence signal. Three different excitation channels are activated. Possible reasons causing the three channels are discussed.

Lai, Zhenhua; Kerimo, Josef; DiMarzio, Charles

2013-02-01

315

Luminescence detection of multiphoton ionization-fragmentation of the molecular CrO  

Microsoft Academic Search

It is shown that luminescence detection of multiphoton ionization-fragmentation of the molecular CrO\\u000a 4\\u000a 2?\\u000a anions adsorbed on the surface of dispersed SiO2 is possible under excitation with the fundamental frequency of a Nd:YAG pulsed laser (?=1.064 ?m). The structure and the process of formation of the adsorbed complexes under thermal activation of the surface and the nature\\u000a of luminescence

Yu. D. Glinka

1997-01-01

316

Characterization of multiphoton laser scanning device optical parameters for image restoration  

NASA Astrophysics Data System (ADS)

Fluorescent nanobeads embedded in agarose and skin biopsies were used to optically characterize spatial and temporal resolution of multiphoton laser scanning devices (MPLSD). Optical sections based on two-photon excited bead fluorescence have been performed at various sample depths. Three-dimensional reconstruction of the image stacks allowed determination of the point spread function. Using calculated point spread functions to apply deconvolution procedures (e.g. Huygens software), the visualization and hence the interpretation of intradermal structures, such as extracellular matrix components in 150 ?m tissue depth, was improved.

Fischer, Frank; Konig, Karsten; Puschmann, Stefan; Wepf, Roger; Riemann, Iris; Ulrich, Volker; Fischer, Peter

2004-09-01

317

Multiphoton dissociation of macromolecular ions at the single-molecule level  

NASA Astrophysics Data System (ADS)

The laser-induced decay of ethylene oxide polymer ions of megadalton size has been studied in the multiphoton IR excitation regime, with fragmentation products of individual ions being monitored over long times by a trapping device. The experiment reveals several fragmentation pathways having distinct signatures at the single-molecule level that would not be accessible from studies based on statistically averaged reaction rates only. The observations are supported by dedicated molecular simulations based on a coarse-grained model, which further highlight the role played by continuous heating in such out-of-equilibrium conditions. In particular, both experiment and modeling indicate that the dissociation kinetics depends nonlinearly on heating rate.

Antoine, Rodolphe; Doussineau, Tristan; Dugourd, Philippe; Calvo, Florent

2013-01-01

318

Multiple-photon excitation imaging with an all-solid-state laser  

NASA Astrophysics Data System (ADS)

Two-photon excitation imaging is a recently described optical sectioning technique where fluorophore excitation is confined to--and therefore defines--the optical section being observed. This characteristic offers a significant advantage over laser-scanning confocal microscopy; the volume of fluorophore excited in the minimum necessary for imaging, thereby minimizing the destructive effects of fluorophore excitation in living tissues. In addition, a confocal pinhole is not required for optical scattering--thus further reducing the excitation needed for efficient photon collection. We have set up a two-photon excitation imaging system which uses an all-solid-state, short-pulse, long-wavelength laser as an excitation source. The source is a diode-pumped, mode-locked Nd:YLF laser operating in the infrared (1047 nm). This laser is small, has modest power requirements, and has proven reliable and stable in operation. The short laser pulses from the laser are affected by the system optical path; this has been investigated with second harmonic generation derived from a nonlinear crystal. The system has been specifically designed for the study of live biological specimens. Two cell types especially sensitive to high-energy illumination, the developing Caenorhabditis elegans embryo and the crawling sperm of the nematode, Ascaris, were used to demonstrate the dramatic increase in viability when fluorescence is generated by two-photon excitation. The system has the capability of switching between two-photon and confocal imaging modes to facilitate direct comparison of theory of these two optical sectioning techniques on the same specimen. A heavily stained zebra fish embryo was used to demonstrate the increase in sectioning depth when fluorescence is generated by infrared two- photon excitation. Two-photon excitation with the 1047 nm laser produces bright images with a variety of red emitting fluorophores, and some green emitting fluorophores, commonly used in biological research. Fortuitously, we have found that at least four blue emitting fluorophores normally excited by UV light are excited by the pulsed 1047 nm laser, by what we believe to be three-photon excitation. Multi-photon excitation is demonstrated by a double labelled C. elegans embryo.

Wokosin, David L.; Centonze, Victoria F.; White, John G.; Hird, Steven N.; Sepsenwol, S.; Malcolm, Graeme P. A.; Maker, Gareth T.; Ferguson, Allister I.

1996-05-01

319

Modified detector tomography technique applied to a superconducting multiphoton nanodetector.  

PubMed

We present an experimental method to characterize multi-photon detectors with a small overall detection efficiency. We do this by separating the nonlinear action of the multiphoton detection event from linear losses in the detector. Such a characterization is a necessary step for quantum information protocols with single and multiphoton detectors and can provide quantitative information to understand the underlying physics of a given detector. This characterization is applied to a superconducting multiphoton nanodetector, consisting of an NbN nanowire with a bowtie-shaped subwavelength constriction. Depending on the bias current, this detector has regimes with single and multiphoton sensitivity. We present the first full experimental characterization of such a detector. PMID:22330516

Renema, J J; Frucci, G; Zhou, Z; Mattioli, F; Gaggero, A; Leoni, R; de Dood, M J A; Fiore, A; van Exter, M P

2012-01-30

320

Three- and Four-Photon Absorption of a Multiphoton Absorbing Fluorescent Probe  

NASA Astrophysics Data System (ADS)

High-order multiphoton excitation processes are becoming a reality for fluorescence imaging and phototherapy treatment because they afford minimization of scattered light losses and a reduction of unwanted linear absorption in the living organism transparency window, making them less susceptible to photodamage, while improving the irradiation penetration depth and spatial resolution. We report the four-photon-excited fluorescence emission of (7-benzothiazol-2-yl-9,-didecylfluoren-2-yl)-diphenylamine in hexane and its four-photon absorption cross section sigma4' = 8.1 × 10^-109 cm8 s3 photon^-3 for the transition S0 ---> S1 when excited at 1600 nm with a tunable optical parametric generator (OPG) pumped by picosecond laser pulses. When pumped at 1200 nm, three-photon absorption was observed, corresponding to the same transition.

Hernández, Florencio E.; Belfield, Kevin D.; Cohanoschi, Ion; Balu, Mihaela; Schafer, Katherine J.

2004-10-01

321

Three- and four-photon absorption of a multiphoton absorbing fluorescent probe.  

PubMed

High-order multiphoton excitation processes are becoming a reality for fluorescence imaging and phototherapy treatment because they afford minimization of scattered light losses and a reduction of unwanted linear absorption in the living organism transparency window, making them less susceptible to photodamage, while improving the irradiation penetration depth and spatial resolution. We report the four-photon-excited fluorescence emission of (7-benzothiazol-2-yl-9,-didecylfluoren-2-yl)diphenylamine in hexane and its four-photon absorption cross section sigma4' = 8.1 x 10(-109) cm8 s3 photon(-3) for the transition S0 --> S1 when excited at 1600 nm with a tunable optical parametric generator (OPG) pumped by picosecond laser pulses. When pumped at 1200 nm, three-photon absorption was observed, corresponding to the same transition. PMID:15495431

Hernández, Florencio E; Belfield, Kevin D; Cohanoschi, Ion; Balu, Mihaela; Schafer, Katherine J

2004-10-01

322

Time-resolved two-color photoacoustic and multiphoton ionization spectroscopy of aniline  

SciTech Connect

The multiphoton ionization and photoacoustic signals from aniline have been detected as a function of time delay between two laser pulses of different wavelength. The first pulse excited the S/sub 0/ ..-->.. S/sub 1/ 0--0 transition. The second pulse either excited S/sub 1/ to a higher singlet state, or a triplet state produced by intersystem crossing to a higher triplet state, depending on the time delay between pulses. Both ionization and dissociation processes are observed. By varying the conditions of excitation it appears that a given amount of energy can be selectively channeled almost exclusively into either ionization or dissociation pathways. The results are explained using a simple Franck--Condon factor model.

Moll, D.J.; Parker, G.R. Jr.; Kuppermann, A.

1984-05-15

323

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

324

Characterization of powdered epidermal vaccine delivery with multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton laser scanning microscopy (MPLSM) has been adapted to non-invasively characterize hand-held powdered epidermal vaccine delivery technology. A near infrared femtosecond pulsed laser, wavelength at approximately 920 nm, was used to evoke autofluorescence of endogenous fluorophores within ex vivo porcine and human skin. Consequently, sub cellular resolution three-dimensional images of stratum corneum and viable epidermal cells were acquired and utilized to observe the morphological deformation of these cells as a result of micro-particle penetration. Furthermore, the distributional pattern of micro-particles within the specific skin target volume was quantified by measuring the penetration depth as revealed by serial optical sections in the axial plane obtained with MPLSM. Additionally, endogenous fluorescence contrast images acquired at the supra-basal layer reveal cellular structures that may pertain to dendritic Langerhans cells of the epidermis. These results show that MPLSM has advantages over conventional histological approaches, since three-dimensional functional images with sub-cellular spatial resolution to depths beyond the epidermis can be acquired non-invasively. Accordingly, we propose that MPLSM is ideal for investigations of powdered epidermal vaccine delivery.

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

2004-11-01

325

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

326

LIME: Flexible, Non-LTE Line Excitation and Radiation Transfer Method for Millimeter and Far-infrared Wavelengths  

NASA Astrophysics Data System (ADS)

LIME solves the molecular and atomic excitation and radiation transfer problem in a molecular gas and predicting emergent spectra. The code works in arbitrary three dimensional geometry using unstructured Delaunay latices for the transport of photons. Various physical models can be used as input, ranging from analytical descriptions over tabulated models to SPH simulations. To generate the Delaunay grid we sample the input model randomly, but weigh the sample probability with the molecular density and other parameters, and thereby we obtain an average grid point separation that scales with the local opacity. Slow convergence of opaque models becomes traceable; when convergence between the level populations, the radiation field, and the point separation has been obtained, the grid is ray-traced to produced images that can readily be compared to observations. LIME is particularly well suited for modeling of ALMA data because of the high dynamic range in scales that can be resolved using this type of grid, and can furthermore deal with overlapping lines of multiple molecular and atomic species.

Brinch, C.; Hogerheijde, M. R.

2011-07-01

327

LIME - a flexible, non-LTE line excitation and radiation transfer method for millimeter and far-infrared wavelengths  

NASA Astrophysics Data System (ADS)

We present a new code for solving the molecular and atomic excitation and radiation transfer problem in a molecular gas and predicting emergent spectra. This code works in arbitrary three dimensional geometry using unstructured Delaunay latices for the transport of photons. Various physical models can be used as input, ranging from analytical descriptions over tabulated models to SPH simulations. To generate the Delaunay grid we sample the input model randomly, but weigh the sample probability with the molecular density and other parameters, and thereby we obtain an average grid point separation that scales with the local opacity. Our code does photon very efficiently so that the slow convergence of opaque models becomes traceable. When convergence between the level populations, the radiation field, and the point separation has been obtained, the grid is ray-traced to produced images that can readily be compared to observations. Because of the high dynamic range in scales that can be resolved using this type of grid, our code is particularly well suited for modeling of ALMA data. Our code can furthermore deal with overlapping lines of multiple molecular and atomic species.

Brinch, C.; Hogerheijde, M. R.

2010-11-01

328

Ultrasensitive Nanosensors Based on Upconversion Nanoparticles for Selective Hypoxia Imaging in Vivo upon Near-Infrared Excitation.  

PubMed

Hypoxia is a distinct feature of malignant solid tumors, which is a possible causative factor for the serious resistance to chemo- and radiotherapy or the development of invasion and metastasis. The exploration of nanosensors with the capabilities like the accurate diagnosis of hypoxic level will be helpful to estimate the malignant degree of tumor and subsequently implement more effective personalized treatment. Here, we report the design and synthesis of nanosensors that can selectively and reversibly detect the level of hypoxia both in vitro and in vivo. The designed nanosensor is composed of two main moieties: oxygen indicator [Ru(dpp)3](2+)Cl2 for detection of hypoxia and upconversion nanoparticles for offering the excitation light of [Ru(dpp)3](2+)Cl2 by upconversion process under 980 nm exposure. The results show that the nanosensors can reversibly become quenched or luminescent under hyperoxic or hypoxic conditions, respectively. Compared with free [Ru(dpp)3](2+)Cl2, the designed nanosensors exhibit enhanced sensitivity for the detection of oxygen in hypoxic regions. More attractively, the nanosensors can image hypoxic regions with high penetration depth because the absorption and emission wavelength are within the NIR and far-red region, respectively. Most importantly, nanosensors display a high selectivity for detection of relevant oxygen changes in cells and zebrafish. PMID:24956326

Liu, Jianan; Liu, Yong; Bu, Wenbo; Bu, Jiwen; Sun, Yong; Du, Jiulin; Shi, Jianlin

2014-07-01

329

Excitation Energy Dependence in Near-infrared Photoluminescence Spectra and Dynamics of PuO{sub 2}{sup 2+} in Cs{sub 2}U(Pu)O{sub 2}Cl{sub 4}  

SciTech Connect

Recently we reported the observation of near-infrared photoluminescence from metal-centered 5f electronic excited states of PuO{sub 2}{sup 2+} doped into polycrystalline Cs{sub 2}U(Pu)O{sub 2}Cl{sub 4}. Photoluminescence dynamics following pulsed excitation show complicated decay patterns suggesting that multiple luminescent states are involved. Here we report the results of two recent sets of experiments showing that photoluminescence processes depend significantly on the energy of photoexcitation. In the first case, decay kinetics following excitation at a lower energy are missing an in-growth term that is present when exciting at higher energy. In the second case, we have observed that lower excitation energy produces significantly reduced number of emission transitions than higher excitation energy. Both observations suggest that higher energy excitation populates feeder states that decay to emitting states, causing signal from the latter to have an in-growth followed by a decay characteristic of their intrinsic lifetimes, whereas lower energy excitation leads to more direct population of luminescent states. (authors)

Berg, John M.; Wilkerson, Marianne P. [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM, 87545 (United States)

2008-07-01

330

Spectroscopic probes of vibrationally excited molecules at chemically significant energies  

SciTech Connect

These experiments apply multiple-laser spectroscopic techniques to investigate the bond energies, potential surface topologies, and dissociation dynamics of highly vibrationally excited molecules. Infrared-optical double resonance pumping of light atom stretch vibrations in H{sub 2}O{sub 2} and HN{sub 3} prepares reactant molecules in single rovibrational states above the unimolecular dissociation threshold on the ground potential surface, and laser induced fluorescence detection of the OH or NH fragments monitors the partitioning of energy into individual product quantum states. Product energy partitioning data from H{sub 2}O{sub 2} dissociation provide a stringent test of statistical theories as well as potential energy surface calculations. Ongoing work on HN{sub 3} seeks to determine the height of the barrier to dissociation on the singlet potential energy surface. Our most recently developed spectroscopic scheme allows the measurement of high vibrational overtone spectra of jet-cooled molecules. This approach uses CO{sub 2} laser infrared multiphoton dissociation followed by laser induced fluorescence product detection to measure weak vibrational overtone transitions in low pressure environments. Application of this scheme to record the {Delta}V{sub OH}=4 and {Delta}V{sub OH}=5 transitions of CH{sub 3}OH cooled in a supersonic free-jet demonstrates both its feasibility and its utility for simplifying high vibrational overtone spectra.

Rizzo, T.R.

1992-03-01

331

Multimodal optoacoustic and multiphoton fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is a powerful imaging modality that enables structural and functional imaging with cellular and sub-cellular resolution, deep within biological tissues. Yet, its main contrast mechanism relies on extrinsically administered fluorescent indicators. Here we developed a system for simultaneous multimodal optoacoustic and multiphoton fluorescence 3D imaging, which attains both absorption and fluorescence-based contrast by integrating an ultrasonic transducer into a two-photon laser scanning microscope. The system is readily shown to enable acquisition of multimodal microscopic images of fluorescently labeled targets and cell cultures as well as intrinsic absorption-based images of pigmented biological tissue. During initial experiments, it was further observed that that detected optoacoustically-induced response contains low frequency signal variations, presumably due to cavitation-mediated signal generation by the high repetition rate (80MHz) near IR femtosecond laser. The multimodal system may provide complementary structural and functional information to the fluorescently labeled tissue, by superimposing optoacoustic images of intrinsic tissue chromophores, such as melanin deposits, pigmentation, and hemoglobin or other extrinsic particle or dye-based markers highly absorptive in the NIR spectrum.

Sela, Gali; Razansky, Daniel; Shoham, Shy

2013-03-01

332

Multiphoton ionization of large water clusters.  

PubMed

Water clusters are multimers of water molecules held together by hydrogen bonds. In the present work, multiphoton ionization in the UV range coupled with time of flight mass spectrometry has been applied to water clusters with up to 160 molecules in order to obtain information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. The dependence of ion intensities of water clusters and their metastable fragments produced by laser ionization at 355 nm on laser power density indicates a (3+1)-photon resonance-enhanced multiphoton ionization process. It also explains the large increase of ionization efficiency at 355 nm compared to that at 266 nm. Indeed, it was found, by applying both nanosecond and picosecond laser ionization with the two different UV wavelengths, that no water cluster sequences after n = 9 could be observed at 266 nm, whereas water clusters up to m/z 2000 Th in reflectron mode and m/z 3000 Th in linear mode were detected at 355 nm. The agreement between our findings on clusters of water, especially true in the range with n > 10, and reported data for liquid water supports the hypothesis that clusters above a critical dimension can approximate the liquid phase. It should thus be possible to study clusters just above 10 water molecules, for getting information on the bulk phase structure. PMID:24880286

Apicella, B; Li, X; Passaro, M; Spinelli, N; Wang, X

2014-05-28

333

Multi-photon entanglement from parametric downconversion  

NASA Astrophysics Data System (ADS)

Several optics experiments at the few-photon level are presented. First, we demonstrate the production of entangled states of up to 100 photons and methods to analyze their entanglement with single photon detectors. We then develop a method to generate path entangled states of light from the output of a parametric downconverter without postselection. We observe the bunching of composite states of photons, and show that they can exhibit bosonic or fermionic behavior depending on their internal phase. We demonstrate a novel way to produce entangled photon pairs that provides unmatched quantum interference visibility when using an ultrafast pump source. We then theoretically analyze the multi-photon state produced with such a source. By using the Schmidt decomposition of the state, we obtain intuitive expressions for four-fold correlation functions and also the non-perturbative solution to the downconversion interaction Hamiltonian. Finally, we present two measurements of the output of a Mach-Zehnder interferometer using a novel multiphoton detector. We show that the individual photon absorption probabilities vary on a subwavelength scale. We also show, using a Bayesian analysis of the detection results, that the phase sensitivity of an interferometer is in fact independent of phase angle, in contrast to the widely used standard theory.

Khoury, George

334

The wide-field optical sectioning of microlens array and structured illumination-based plane-projection multiphoton microscopy.  

PubMed

We present a theoretical investigation of an optical microscope design that achieves wide-field, multiphoton fluorescence microscopy with finer axial resolution than confocal microscopy. Our technique creates a thin plane of excitation light at the sample using height-staggered microlens arrays (HSMAs), wherein the height staggering of microlenses generate temporal focusing to suppress out-of-focus excitation, and the dense spacing of microlenses enables the implementation of structured illumination technique to eliminate residual out-of-focus signal. We use physical optics-based numerical simulations to demonstrate that our proposed technique can achieve diffraction-limited three-dimensional imaging through a simple optical design. PMID:23389190

Yu, Jiun-Yann; Holland, Daniel B; Blake, Geoffrey A; Guo, Chin-Lin

2013-01-28

335

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

336

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

337

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

338

An adaptive approach for uniform scanning in multifocal multiphoton microscopy with a spatial light modulator.  

PubMed

We propose high-quality generation of uniform multiple fluorescence spots (MFS) with a spatial light modulator (SLM) and demonstrate uniform laser scanning in multifocal multiphoton microscopy (MMM). The MFS excitation method iteratively updates a computer-generated hologram (CGH) using correction coefficients to improve the fluorescence intensity distribution in a dye solution whose consistency is uniform. This simple correction method can be applied for calibration of the MMM before observation of living tissue. We experimentally demonstrate an improvement of the uniformity of a 10 × 10 grid of MFS by using a dye solution. After the calibration, we performed laser scanning with two-photon excitation to observe fluorescent polystyrene beads, as well as the gastric gland of a guinea pig specimen. PMID:24515023

Matsumoto, Naoya; Okazaki, Shigetoshi; Fukushi, Yasuko; Takamoto, Hisayoshi; Inoue, Takashi; Terakawa, Susumu

2014-01-13

339

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

NASA Astrophysics Data System (ADS)

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

Purnapatra, Subhajit B.; Pratim Mondal, Partha

2013-07-01

340

Infrared-laser-pulse control of bond- and state-selective excitation, dissociation and space quantization: application to a three-dimensional model of HONO2 in the ground electronic state  

Microsoft Academic Search

.   Selective control over the vibrational excitation and space quantization of the dissociation fragments by optimally designed\\u000a linearly polarized and shaped infrared (IR) laser pulses of the picosecond (ps) and subpicosecond duration is demonstrated\\u000a by means of quantum-dynamical simulations within the Schrödinger wave-function formalism for a three-dimensional (3-D) model\\u000a of HONO2 in the ground electronic state, wherein the OH and

M. Oppel; G. K. Paramonov

2000-01-01

341

Multiphoton imaging of biological samples during freezing and heating  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

342

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

343

New Directions in 3-D Multiphoton Lithography.  

NASA Astrophysics Data System (ADS)

Multiphoton absorption polymerization (MAP) is a promising technique for the lithographic fabrication of 3-D microdevices. However, this technique also has two major shortcomings that have so far precluded its use in the mass production of devices. First, MAP is an inherently serial technique, and structures must be created on a voxel-by-voxel basis. Second, the fabrication of many desirable 3-D devices requires incorporation of materials other than polymers. We will discuss our recent progress in attacking both of these problems. We have developed soft-lithographic techniques that allow for the creation of complex 3-D structures that can include closed loops based on master structures created using MAP. We have also developed a technique that allows for the selective deposition of materials that include metals, metal oxides, and biomolecules on desired regions of 3-D structures fabricated with MAP. We demonstrate the use of the latter technique in the creation of functional microinductors.

Fourkas, John; Lafratta, Christopher; Farrer, Richard; Li, Linjie; Naughton, Michael

2006-03-01

344

Microwave multiphoton transitions between Rydberg states driven by chirped pulses  

Microsoft Academic Search

We observe microwave multiphoton transitions in Rydberg states of potassium using intense pulses of chirped microwave radiation. Pulses of microwaves with frequencies between 0.6 and 0.9 GHz with frequency chirp times from 5 ns (4 cycles) to 200 ns (150 cycles) are generated with peak fields of 15 V\\/cm. We are able to drive high order multiphoton transitions using these

C. W. S. Conover; M. C. Doogue; D. A. Perry

1998-01-01

345

Generation of High-Order Squeezing in Multiphoton Micromaser  

NASA Technical Reports Server (NTRS)

The generation of steady state higher-order squeezing in the sense of Hong and Mandel and also of Hillery in a multiphoton micromaser is studied. The results show that the cotangent state which is generated by the coherent trapping scheme in a multiphoton micromaser can exhibit not only second-order squeezing but also fourth-order and squared field amplitude squeezings. The influence of the cavity loss on the squeezings is investigated.

Li, Fu-Li; Huang, Qing

1996-01-01

346

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

347

Optical Diagnosis for Lung Cancer Using Multiphoton Imaging.  

PubMed

Currently, hematoxylin-eosin (H-E) stained histopathology is the golden standard for diagnosing lung cancer. This time-consuming procedure needs tissue biopsy, sample fixation, slicing, and labeling. Therefore, the availability of a noninvasive optical diagnosis that can obtain real-time analysis comparable to golden standard H-E stained histopathology will be of extraordinary benefit to the medical community. In this study, we investigated whether multiphoton imaging can make real-time optical diagnosis for normal and cancerous lung tissue, compared with H-E stained histopathology. In the normal lung tissue, we found that multiphoton imaging could display normal lung parenchyma composed of alveolar spaces separated by thin septa. In the cancerous lung tissue, multiphoton imaging clearly illustrated that cancer cells displayed marked cellular and nuclear pleomorphism. These cancer cells were characterized by irregular size and shape, enlarged nuclei, and increased nuclear-cytoplasmic ratio. All of these histopathological features of tissue architecture and cell morphology identified by multiphoton images were readily correlated with H-E staining images. All together, multiphoton imaging can make real-time optical diagnosis for lung cancer. This study provides the groundwork for further using multiphoton imaging to perform real-time noninvasive "optical biopsy" for lung cancer in the near future. SCANNING 9999:XX-XX, 2013. © 2013 Wiley Periodicals, Inc. PMID:23427040

Chen, Gang; Wang, Linghua; Lu, Jianping; Zhu, Weifeng; Zhang, Hui; Chen, Jianxin; Zhuo, Shuangmu; Yan, Jun

2013-02-20

348

New photocalorimetric references for UV excitation  

NASA Astrophysics Data System (ADS)

A set of calorimetric references for excitation at ? = 266 nm in acetonitrile solutions is proposed. Theophylline and several purinic compounds (purine, 6-methylpurine, 6-methoxypurine, 6-chloropurine, and 6-aminopurine) were investigated using pulsed laser optoacoustic spectroscopy with resolution times between 150 ns and 1 ?s and compared with 2-hydroxybenzophenone. At room temperature, all these compounds show no fluorescence, good stability and no photochemical processes as photodegradation or multiphotonic effects below fluences of 1000 J/m 2.

Murgida, D. H.; Erra-Balsells, R.; Bilmes, G. M.

1996-02-01

349

Particle modeling of microplasma generated by resonance enhanced multiphoton ionization  

NASA Astrophysics Data System (ADS)

Resonance-enhanced multiphoton ionization (REMPI) is a technique applied to the spectroscopy of atoms. The REMPI technique typically involves a resonant single or multiple photon absorption to an electronically excited intermediate state followed by another photon which ionizes the atom. Rayleigh scattering of REMPI plasma has given rise to a non-intrusive, time accurate measurement of electron formation and loss, which lead to many applications viz. trace species detection and micro-plasma diagnostics. It is very important to quantify the expansion process and the evolution of energy of electrons and ions. The operation scale of this process is in microns and non continuum nature of the process lead to the use of PIC/MCC scheme to compu- tationally model REMPI technique. This work attempts to understand and analyze the processes taking place during the expansion of REMPI plasma computationally using the PIC/MCC scheme. One dimensional and two dimensional approximations are considered to analyze the REMPI plasma expansion in Argon gas generated by a laser with a focal shape of a prolate ellipsoid. The expansion of the plasma is found to be very sensitive to the initial velocity distribution of the electrons. REMPI plasma expansion is shown to be ambipolar in nature, with the radial expansion more predominant than axial expansion, hence requiring the 2D model. Electron energy distribution functions(EEDFs) are found at various radial locations along with the corresponding mean energies. The deviation of the EEDFs from that of equilibrium Maxwell-Boltzmann energy distribution is presented both qualitatively and quanti- tatively, indicating the predominant processes at various instances in time.

Tholeti, Siva Sashank

350

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.

2012-02-01

351

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

PubMed Central

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

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

2014-01-01

352

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

PubMed Central

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

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

2013-01-01

353

Multiphoton microscopy for the investigation of trans-cutaneous drug delivery  

NASA Astrophysics Data System (ADS)

The trans-cutaneous pathway for drug delivery is of particular interest since it allows a simple and non-invasive administration of pharmaceutically relevant compounds. As the skin is an effective barrier for many of these compounds, various strategies have been developed to enable and control the trans-cutaneous transport. Here we discuss, how multiphoton microscopy and spectral imaging can be valuable tools for the analysis of the penetration pathways of topically applied drugs. A time dependent study of the cutaneous penetration of a fluorescent drug model released from a nano-particular carrier is presented. The localization of single nano-particles in human skin (ex vivo) and the discrimination of different fluorescent compounds, as the drug model, the particle's label and the cutaneous endofluorescence by spectral imaging and selective excitation is shown. Multiphoton imaging techniques were found to be excellent methods for the non-invasive evaluation of cutaneous drug delivery strategies and analysis of dermal penetration pathways down to the sub-cellular level.

Stracke, Frank; Schneider, Marc; Weiss, Barbara; Lehr, Claus-Michael; Schäfer, Ulrich F.; König, Karsten

2007-07-01

354

Multiphoton spectral analysis of benzo[a]pyrene uptake and metabolism in breast epithelial cell lines  

PubMed Central

Quantification of polycyclic aromatic hydrocarbons (PAH) and their metabolites within living cells and tissues in real time using fluorescence methods is complicated due to overlaping excitation and/or emission spectra of metabolites. In this study, simultaneous analysis of several metabolites of a prototype carcinogenic PAH, benzo[a]pyrene (BaP) in undifferentiated (MCF10A) and differentiated (MCF10CA1h) breast cancer cells was performed using single-cell multiphoton spectral analysis. The two cell types were selected for this study because they are known to have differences in BaP uptake and metabolism and induction of aryl hydrocarbon receptor-dependent ethoxyresorufin-O-deethylase (EROD) activity. Multiphoton microscopy spectral analysis performed in cells exposed to BaP for 24 hr identified 5 major peaks of fluorescence that were monitored within spectral bands. A comparison of the fluorescence peaks within these bands to those of BaP metabolite standards indicated that a peak in the spectral range of 393–415 nm matched benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide(±),(anti) (BPDE), the ultimate carcinogenic BaP metabolite. In addition, the 426–447 nm band matched the major metabolites 3-hydroxybenzo[a]pyrene (3-OH BaP) and 9-hydroxybenzo[a]pyrene (9-OH BaP); the 458–479 nm band corresponded to the secondary metabolite benzo[a]pyrene-3,6-dione (3,6 BPQ); and a peak at 490–530 nm matched the parent compound, BaP. Multiphoton spectral analysis also revealed differences in fluorescence intensities between MCF10A and MCF10CA1h cells within three spectral bands: 393–415 nm, 426–447 nm and 458–479 nm which were partially reversed with cyclosporine A suggesting differences in efflux mechanisms between cell lines. These results demonstrate the feasibility of analyzing BaP metabolism in situ by multiphoton spectral analysis and also identifying cell-type differences in BaP accumulation and metabolism.

Barhoumi, Rola; Catania, Jeffrey M.; Parrish, Alan R.; Awooda, Igbal; Tiffany-Castiglioni, Evelyn; Safe, Stephen; Burghardt, Robert C.

2009-01-01

355

New perspectives in laser analytics: Resonance-enhanced multiphoton ionization in a Paul ion trap combined with a time-of-flight mass spectrometer  

NASA Astrophysics Data System (ADS)

A new laser analytical device has been developed that is based on resonance-enhanced multiphoton ionization in the very center of a radio-frequency quadrupole ion trap. Applications in speciation anlaysis of biological and enviromental samples and in materials science will all benefit from laser-optical selectivity in the resonance excitation process, combined with mass-spectropic sensivity which is further enhanced by the ion accumulation and storage capability.

Bisling, Peter; Heger, Hans Jörg; Michaelis, Walfried; Weitkamp, Claus; Zobel, Harald

1995-04-01

356

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

357

Multiphoton signatures of goldstini at the LHC  

NASA Astrophysics Data System (ADS)

We study models of gauge mediated SUSY breaking with more than one hidden sector. In these models the neutralino sector of the MSSM is supplemented with additional light neutral fermions, the nearly massless gravitino and the massive pseudo-goldstini. For the case where the Bino is the lightest ordinary SUSY particle, its preferred decay is to a photon and the heaviest pseudo-goldstino, which generically cascades down to lighter pseudo-goldstini, or to the gravitino, in association with photons. This gives rise to multiphoton plus missing energy signatures at the LHC. We investigate in detail simplified models where the SUSY spectrum consists of the right-handed sleptons, a Bino-like neutralino, the pseudo-goldstini and the gravitino. We compare against existing LHC searches and show that the sensitivity to our models could be significantly improved by relaxing the kinematic cuts and requiring additional final state particles. We propose inclusive searches in the final states (?3) ? + [InlineMediaObject not available: see fulltext.] T and ? + ? - + (?2) ? + [InlineMediaObject not available: see fulltext.] T , the former being sensitive to any production mode and the latter being optimized for slepton pair production. We show that they could lead to an observation (or strong constraints) already with the data set from LHC Run I, and present prospects for LHC Run II.

Ferretti, Gabriele; Mariotti, Alberto; Mawatari, Kentarou; Petersson, Christoffer

2014-04-01

358

A large area liquid scintillation multiphoton detector  

NASA Astrophysics Data System (ADS)

A 60 layer lead-liquid scintillator shower detector, which we call the SLIC, has been used for multiphoton detection in the Fermilab tagged photon spectrometer. The detector has an unimpeded active area which is 2.44 m by 4.88 m and is segmented, by means of teflon coated channels, into 3.17 cm wide strips. The 60 layers in depth are broken into three directions of alternating readouts so that three position coordinates are determined for each shower. At present the readouts are made by 334 photomultiplier tubes coupled to BBQ doped wavelength shifter bars which integrate the entire depth of the detector. It is relatively straightforward to increase the number of readouts to include longitudinal segmentation and to increase the segmentation of the outer region which are at present read out two strips to a readout. The energy and position resolutions of isolated showers are about {12%}/{?E} and 3 mm., respectively. The SLIC has been used to study the K-?+?0 decay of the D 0 [1], as well as for electron and muon identification in ? ? e +e - and ? ? ?+?- plus ?0 identification in ?p ? ?? [8].

Bharadwaj, V. K.; Cain, M. P.; Caldwell, D. O.; Denby, B. H.; Eisner, A. M.; Joshi, U. P.; Kennett, R. G.; Lu, A.; Morrison, R. J.; Pfost, D. R.; Stuber, H. R.; Summers, D. J.; Yellin, S. J.; Appel, J. A.

1985-01-01

359

Unconditionally secure key distillation from multiphotons  

SciTech Connect

In this paper, we prove that the unconditionally secure key can be surprisingly extracted from multiphoton emission part in the photon polarization-based quantum key distribution. One example is shown by explicitly proving that one can indeed generate an unconditionally secure key from Alice's two-photon emission part proposed by Scarani [et al. Phys. Rev. Lett. 92, 057901 (2004)]. Which is called the Scarani-Acin-Ribordy-Gisin (SARG04) protocol. This protocol uses the same four states as in Bennett-Brassard 1984 (BB84) and differs only in the classical postprocessing protocol. It is, thus, interesting to see how the classical postprocessing of quantum key distribution might qualitatively change its security. We also show that one can generate an unconditionally secure key from the single to the four-photon part in a generalized SARG04 protocol that uses six states. Finally, we also compare the bit error rate threshold of these protocols with the one in the BB84 protocol and the original six-state protocol assuming a depolarizing channel.

Tamaki, Kiyoshi; Lo, Hoi-Kwong [Center for Quantum Information and Quantum Control, Department of Electrical and Computer Engineering and Department of Physics, University of Toronto, Toronto, Ontario, M5S 3G4 (Canada)

2006-01-15

360

Dichroism in short-pulse two-color XUV plus IR multiphoton ionization of atoms  

NASA Astrophysics Data System (ADS)

Circular and linear dichroism in the angular distributions of photoelectrons in multiphoton ionization of unpolarized atoms by a combination of two short pulses in the extreme ultraviolet (XUV) and infrared (IR) range is theoretically considered. A noticeable circular dichroism is predicted in the case when both XUV and IR pulses are circularly polarized. Here the dichroism may be observed not only in angle-resolved but also in angle-integrated experiments. When the XUV photons are linearly polarized while the IR pulses are circularly polarized, the circular dichroism can be observed only in angle-resolved experiments. In this case the dichroism averaged over a spectral line is small. When both pulses are linearly polarized, the photoelectron yield strongly depends on the angle between the polarizations, which leads to the considerable linear dichroism.

Kazansky, A. K.; Grigorieva, A. V.; Kabachnik, N. M.

2012-05-01

361

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

362

Multiphoton photoconductivity and optical nonlinearities in ZnSe and CdSe direct band gap crystals  

NASA Astrophysics Data System (ADS)

The multiphoton photoconductivity properties of ZnSe and CdSe direct band gap crystals have been studied using frequency-doubled Nd:YAG laser excitation. Two-photon absorption in both crystals has been observed. The photoconductivity measurements and nonlinearity in Z-scan traces confirms the existence of a lower valence band, from where one-photon transitions are forbidden but two-photon transitions are allowed. The value of the two-photon absorption cross section ?2 in both crystals has been calculated by using second-order time-dependent perturbation theory.

Gaur, Arun; Sharma, D. K.; Ahlawat, D. S.; Singh, Nageshwar

2007-03-01

363

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

PubMed

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 ? 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. PMID:23145725

Zhang, Shian; Lu, Chenhui; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

2012-11-01

364

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

NASA Astrophysics Data System (ADS)

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

Wang, Jingyan

365

Excitation efficiency and saturation dynamics of near-infrared emission from Si nanocrystals embedded in a SiO2-matrix  

NASA Astrophysics Data System (ADS)

We have investigated photoluminescence (PL) and linear and induced absorption of Si nanocrystals (NCs) in a SiO2 matrix. By measuring PL intensity dependence on the excitation photon fluence, we conclude that (i) the excitation wavelength independent saturation level is reached when on average a single photon is absorbed per NC, and (ii) excitation cross-section is proportional to the linear absorption only in the low-energy range; for higher energy it increases faster than absorption, thus indicating more efficient excitation which appears due to space-separated quantum cutting (SSQC). In order to shed more light on the mechanism behind the SSQC, we have compared spectral and temporal characteristics of induced absorption for excitation wavelengths below and above the SSQC threshold. These were found to be very similar, thus indicating that the SSQC process is most likely very fast, possibly taking place already during photon absorption by NCs.

Timmerman, D.; de Boer, W. D. A. M.; Gregorkiewicz, T.

2009-05-01

366

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

367

Multiphoton photochemical and collisional effects during oxygen-atom flame detection.  

PubMed

A Nd:YAG-pumped dye-laser system was used to two-photon excite oxygen atoms at 225.6 nm in an atmosphericpressure CH(4)-N(2)O-N(2) flame. Subsequent emission at 844.7 nm from the directly populated state as well as a stronger emission at 777.5 nm that was due to the O(3p(3)P ? 3p(5)P) collisional-energy transfer process was monitored. Two-photon-resonant oxygen-atom and hydrogen-atom (656.3-nm) emissions were also observed in the absence of a flame. Closer examination revealed that the tightly focused probe beam was producing these atoms by promoting multiphoton photolysis of the oxidizer as well as of the fuel molecules. Thus this type of laser-diagnostic probe is potentially quite intrusive, depending on the combustion region that is probed as well as on the laser energies used. PMID:19721609

Miziolek, A W; Dewilde, M A

1984-09-01

368

Enhanced ionization of hydrogen molecular ions in an intense laser field via a multiphoton resonance  

SciTech Connect

Multiphoton ionization of hydrogen molecular ions in a 480-nm intense laser field is investigated by solving the time-dependent Schroedinger equation numerically in prolate spheroidal coordinates. We discretize space on a generalized pseudospectral grid and propagate the electronic wave function using a second-order split-operator method. By including and excluding the 2psigma{sub u} state in the basis expansion, we confirm that the observed 10-eV peak in a recent experiment [Litvinyuk et al., New J. Phys. 10, 083011 (2008)] comes from the enhanced ionization via three-photon resonant excitation of the molecular ions. By folding the calculated ionization rates with the vibrational density distribution, the kinetic energy release spectra are obtained, which are in reasonable agreement with the experimental measurement. Furthermore, using this enhanced ionization, a pump-probe experiment is suggested to trace the vibrational wave packet.

Jin Yingjun; Toshima, Nobuyuki [Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Tong Xiaomin [Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

2010-01-15

369

Multiphoton microscopy using frequency-doubled compact femtosecond erbium-doped fiber laser  

NASA Astrophysics Data System (ADS)

We report on the development of a compact multiphoton microscopy (MPM) system based on a frequency-doubled, femtosecond erbium-doped fiber laser source at 1.58 ?m. By use of periodically poled MgO:LiNbO3, frequency-doubled pulses at 790 nm with average power of 75 mW and pulse width of 130 fs are applied as the excitation source. The fiber laser is optimized for its parameters along with the dispersive properties of the delivery fiber such that the MPM signal is maximized at the sample location. Micro-electro-mechanical system (MEMS) scanner, miniature objective, and multimode fiber are further used to make the MPM system compact. MPM images are obtained from unstained biological samples. The MPM system with a compact, portable, low-cost fiber laser has a great potential to transform the bench-top MPM system to a portable system for in vivo MPM imaging.

Huang, Lin; Chong, Shau Poh; Mills, Arthur; Jones, David; Tang, Shuo

2014-02-01

370

Photoelectron imaging and (2 + 1) resonance enhanced multiphoton ionization spectroscopy study of 2-butanone photoionization dynamics.  

PubMed

(2 + 1) Resonance enhanced multiphoton ionization (REMPI) spectra were recorded for 2-butanone to study its photoionization dynamics. Two-photon excitation (53,200-55,000 cm(-1) and 57,000-59,500 cm(-1)) was used to prepare the molecule in the 3s and 3p Rydberg states, respectively. Vibrational transitions in the spectrum were assigned with the aid of ab initio calculations as well as photoelectron imaging results. Photoelectron imaging data in the 3s Rydberg region exhibits a vibrational progression in the CCOC deformation mode in the ionic state superimposed on an otherwise diagonal (delta v = 0) ionization. Photoelectron imaging data in the 3p Rydberg region shows 3p-3s Rydberg-Rydberg mixing. The ionization energy obtained directly from the 3p photoelectron imaging is 9.541 eV. PMID:20078050

Shen, Lei; Zhang, Bailin; Suits, Arthur G

2010-03-11

371

Signal enhancement in multiphoton TIRF microscopy by shaping of broadband femtosecond pulses.  

PubMed

We demonstrate that pulse shaping of a broadband Ti:sapphire laser can result in almost an order of magnitude increase in the sensitivity and signal to background ratio (SBR) of multiphoton total internal reflection fluorescence (TIRF) microscopy. We produced transform-limited pulses of 15 fs duration at the sample, and observed a 8-fold enhancement in the fluorescence of CdSe/ZnS quantum dots via two-photon objective-type TIRF excitation. There was a concomitant 6-fold increase of the SBR upon compression of the pulse duration. Enhancement of non-linear evanescent imaging has recently been demonstrated using surface-plasmons [Opt. Express 17, 5987 (2009)] and structured substrates [Opt. Express 18, 23218 (2010)]. Our approach of ultrafast pulse shaping could be used alone or combined with these new methods to offer significant gains in image quality. PMID:23187410

Lane, Richard S K; Macpherson, Alisdair N; Magennis, Steven W

2012-11-01

372

Remote focusing for programmable multi-layer differential multiphoton microscopy  

PubMed Central

We present the application of remote focusing to multiphoton laser scanning microscopy and utilize this technology to demonstrate simultaneous, programmable multi-layer imaging. Remote focusing is used to independently control the axial location of multiple focal planes that can be simultaneously imaged with single element detection. This facilitates volumetric multiphoton imaging in scattering specimens and can be practically scaled to a large number of focal planes. Further, it is demonstrated that the remote focusing control can be synchronized with the lateral scan directions, enabling imaging in orthogonal scan planes.

Hoover, Erich E.; Young, Michael D.; Chandler, Eric V.; Luo, Anding; Field, Jeffrey J.; Sheetz, Kraig E.; Sylvester, Anne W.; Squier, Jeff A.

2010-01-01

373

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

374

Rotational multiphoton endoscopy with a 1 ?m fiber laser system  

PubMed Central

We present multiphoton microendoscopy with a rotational probe and a 1 ?m fiber-based femtosecond laser. The rotational probe is based on a double-clad photonic crystal fiber, a gradient index lens, a microprism, and a rotational microelectronicmechanical system (MEMS) motor. The MEMS motor has a diameter of 2.2 mm and can provide 360° full-view rotation. The fiber laser provides ultrashort pulses with a central wavelength at 1.034 ?m and a repetition rate of 50 MHz. Second-harmonic-generation images of rat-tail tendon and fish scale are demonstrated with the rotational probe-based multiphoton system.

Liu, Gangjun; Xie, Tuqiang; Tomov, Ivan V.; Su, Jianping; Yu, Lingfeng; Zhang, Jun; Tromberg, Bruce J.; Chen, Zhongping

2009-01-01

375

One- and multi-photon cycloreversion reaction dynamics of diarylethene derivative with asymmetrical structure, as revealed by ultrafast laser spectroscopy.  

PubMed

A cycloreversion reaction of a photochromic diarylethene derivative, 1-(2-methyl-3-benzothienyl)-2-(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene, with asymmetrical structure, in n-hexane solution, was investigated by means of picosecond and femtosecond laser spectroscopic methods. Femtosecond laser spectroscopy revealed that the excited state (S(1)) of the closed form with a lifetime of 1.3 ps undergoes the cycloreversion reaction in competition with the internal conversion and the apparent reaction yield was independent of the excitation intensity. On the other hand, picosecond laser excitation at 532 nm led to the drastic enhancement of the cycloreversion reaction yield by a successive two-photon absorption process via the S(1) state, leading to higher excited states with a large cycloreversion yield of 0.60 +/- 0.1. For the multiphoton-enhanced cycloreversion reaction, we reported that the efficient cycloreversion reaction of a diarylethene derivative with C(2v) symmetry could occur by stepwise, visible two-photon excitation but did not take place by UV one-photon absorption to a higher excited state. In the present asymmetrical system, both UV one-photon and visible two-photon absorption opened the efficient cycloreversion reaction. Similarities and differences of the reaction profiles in higher excited states between diarylethene derivatives with symmetrical and asymmetrical structures are discussed from the viewpoint of the selection rule of optical transition and its dependence on molecular structures. PMID:19421520

Ishibashi, Yukihide; Mukaida, Masayuki; Falkenström, Magnus; Miyasaka, Hiroshi; Kobatake, Seiya; Irie, Masahiro

2009-04-21

376

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

377

Landau-Dykhne approximation for multiphoton dipole-forbidden transitions  

NASA Astrophysics Data System (ADS)

A two-level system in a monochromatic laser field is considered in the Landau-Dykhne approximation under the violation of dipole selection rules. An analytic expression is obtained for the rate of transitions. The multiphoton and tunneling limits are found.

Zon, B. A.; Kornev, A. S.

2007-06-01

378

Laser-induced multiphoton dissociation of n-butyl ether  

NASA Astrophysics Data System (ADS)

The pulsed CO 2-laser-induced multiphoton dissociation of n-butyl vinyl ether is studied. Comprehensive measurements have been performed for 9.6.?m and 10.6 ?m irradiation. The corresponding dissociation product distributions show distinct differences for the two irradiation wavelengths, the most important finding being that acetylene is only produced at 9.6 ?m.

Hofmann, Hubert; Kl?ffer, Waiter; Sch?fer, Gerhard; Gloor, Jean

1981-04-01

379

Coherent population transfer by multiphoton adiabatic rapid pasasage  

Microsoft Academic Search

Coherent population transfer in an atom through a range of states using a sequence of adiabatic rapid passage by single-photon resonances is well known, and it requires the frequency sweep match the changing the frequencies of the atomic transition [1]. The same population transfer can be effected via single multiphoton adiabatic rapid passage, which requires only a small frequency sweep

H. Maeda; J. H. Gurian; D. V. L. Norum; T. F. Gallagher

2006-01-01

380

Laser-induced multiphoton processes in living cells.  

PubMed Central

It is shown that specific light-induced subcellular alterations, usually referred to as phase "paling," result from multiphoton absorption processes. For green light (532 nm), four photons are required to induce paling in chromosomes and nucleoli; a two-photon process is observed for UV light (266 nm).

Calmettes, P P; Berns, M W

1983-01-01

381

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

382

Basics of multiphoton effects in coherent radiation spectra  

NASA Astrophysics Data System (ADS)

Differences between classically calculated radiation spectra of coherent radiation sources and their calorimetrically measured counterparts are discussed in a nutshell. Properties of photon multiplicity spectra are highlighted. The high-intensity limit is analyzed. A simple model for quick estimates of multiphoton effects in coherent radiation spectra is given.

Bondarenco, M. V.

2014-05-01

383

Improvement of depth resolution on photoacoustic imaging using multiphoton absorption  

Microsoft Academic Search

Commercial imaging systems, such as computed tomography and magnetic resonance imaging, are frequently used powerful tools for observing structures deep within the human body. However, they cannot precisely visualized several-tens micrometer-sized structures for lack of spatial resolution. In this presentation, we propose photoacoustic imaging using multiphoton absorption technique to generate ultrasonic waves as a means of improving depth resolution. Since

Yoshihisa Yamaoka; Katsuji Fujiwara; Tetsuro Takamatsu

2007-01-01

384

Excitation with Effective Subcycle Laser Pulses  

NASA Astrophysics Data System (ADS)

We have used laser pulses with a temporally shaped polarization to demonstrate the multiphoton excitation of the xenon 5g state within a subcycle of a laser pulse. Our polarization gated laser pulses are composed of circularly polarized sections at the leading and trailing edges of the pulse and of an experimentally defined linearly polarized central part. Only the linear part (the gate) of the pulse can excite neutral xenon in the 5g state. The transition cannot be driven with circularly polarized light because the number of photons needed would cause a violation of selection rules for the change of the magnetic quantum number. We show that the linearly polarized central part can be reduced to a subcycle pulse. This allows us to study excitation with an effective pulse as short as 2.3 fs at 800 nm. Electron imaging spectroscopy has been used to visualize the presence of excited states as a function of the pulse duration of the gate.

Marceau, C.; Gingras, G.; Witzel, B.

2013-11-01

385

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

386

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

387

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

388

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

PubMed

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

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

2013-07-01

389

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

390

Bandgap dependence in the multiphoton absorption coefficient of semiconductors  

NASA Astrophysics Data System (ADS)

Reports of two and three photon absorption coefficients in common semiconductors show a remarkably large lack of agreement and lack of scaling, indicating the need for more controlled experiments. We report nonlinear photon absorption in single-crystal Si, GaAs, and Ge carried out under identical conditions using an ultrafast high-power mid-IR laser. Wavelength- and bandgap-dependent multiphoton absorption coefficients were extracted and compared to current literature values, as well as the simpler scaling predictions for different bandgap materials. Our experimental data support the theoretical scaling law for the bandgap-dependent multiphoton absorption coefficients. Importantly, our coefficients are approximately 2 orders of magnitude smaller than current literature values.

Seo, Dongmin; Gregory, Justin; Feldman, Leonard; Tolk, Norman; Cohen, Philip

2010-03-01

391

Multiphoton intravital microscopy to study lymphocyte motility in lymph nodes.  

PubMed

Intravital microscopy (IVM) allows for the direct in vivo visualization of dynamic biological processes in their physiological context at high spatial and temporal resolution. Novel nonlinear optical imaging modalities, most prominently multiphoton microscopy, have extended the spectrum of cellular functions amenable to IVM investigation to include migration and cell-cell interactions occurring deep inside the highly light-scattering environments of solid tissues, which had so far been inaccessible to conventional microscopy techniques. This has led to important new insights into immune cell behavior at steady state, as well as their change in behavior during an immune response. Here, we describe in detail a technique that allows for the monitoring of lymphocyte motility in the lymph nodes of mice at the single cell level using multiphoton intravital microscopy (MP-IVM). PMID:21909917

Murooka, Thomas T; Mempel, Thorsten R

2012-01-01

392

Multiphoton core ionization dynamics of polyatomic molecules  

NASA Astrophysics Data System (ADS)

The two-photon core ionization dynamics of gas-phase methane, carbon monoxide and nitrogen have been studied with a recent implementation of the lowest order perturbation theory in the framework of density functional theory and a multicentric basis set expansion of bound and scattering states. Ionization cross sections and angular asymmetry parameters have been calculated for the case of a single radiation beam and for both linear and circular light polarizations in the fixed nuclei approximation. Expected resonances due to core valence excitations enhance the cross section by several orders of magnitude.

Toffoli, Daniele; Decleva, Piero

2013-07-01

393

Resonantly enhanced multiphoton ionization and zero kinetic energy photoelectron spectroscopy of chrysene: a comparison with tetracene.  

PubMed

We report the electronic and vibrational spectroscopy of chrysene using resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. As an isomer of tetracene, chrysene contains a kink in the middle of the four fused hexagonal rings, which complicates not just the symmetry but, more importantly, the molecular orbitals and hence vibronic transitions. Incidentally, the two nearby electronically excited states of chrysene have the same symmetry, and vibronic coupling introduces no out-of-plane vibrational modes. As a result, the REMPI spectrum of chrysene contains essentially only in-plane ring deformation modes, similar to that of tetracene. However, density functional calculations using gaussian even after the inclusion of vibronic coupling can only duplicate the observed REMPI spectrum in a qualitative sense, and the agreement is considerably worse than our recent work on a few pericondensed polycyclic aromatic hydrocarbons and on tetracene. The ZEKE spectrum of chrysene via the origin band of the intermediate electronic state S(1), however, can be qualitatively reproduced by a straightforward Franck-Condon calculation. The ZEKE spectra from vibrationally excited states of the S(1), on the other hand, demonstrate some degree of mode selectivity: the overall intensity of the ZEKE spectrum can vary by an order of magnitude depending on the vibrational mode of the intermediate state. A scaling factor in the theoretical vibrational frequency for the cation is also needed to compare with the experimental result, unlike tetracene and pentacene. PMID:22646822

Zhang, Jie; Harthcock, Colin; Kong, Wei

2012-07-01

394

Multiphoton multifocal microscopy exploiting a diffractive optical element.  

PubMed

Multiphoton multifocal microscopy (MMM) usually has been achieved through a combination of galvo scanners with microlens arrays, with rotating disks of microlens arrays, and cascaded beam splitters with asynchronous rastering of scanning mirrors. Here we describe the achievement of a neat and compact MMM by use of a high-diffraction-efficiency diffractive-optic element that generates a multiple-spot grid of uniform intensity to achieve higher fidelity in imaging of live cells at adequate speeds. PMID:14587775

Sacconi, L; Froner, E; Antolini, R; Taghizadeh, M R; Choudhury, A; Pavone, F S

2003-10-15

395

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

396

Collisionless Multiphoton Dissociation of SF6: A Statistical Thermodynamic Process  

Microsoft Academic Search

A calorimetric experiment, which combines picosecond CO2-laser pulses with acoustic detection techniques, proves that the collisionless multiphoton dissociation of SF6 is a statistical thermodynamic process. The standard Rice-Ramsberger-Kassel-Marcus theory of unimolecular reactions provides a quantitative explanation of the dissociation effect. The reaction rate is primarily limited by transitions in the quasicontinuum rather than by the anharmonicity of the first few

N. Bloembergen; Eli Yablonovitch; S. Mukamel

1977-01-01

397

Measurement-induced quantum operations on multiphoton states  

SciTech Connect

We investigate how multiphoton quantum states obtained through optical parametric amplification can be manipulated by performing a measurement on a small portion of the output light field. We study in detail how the macroqubit features are modified by varying the amount of extracted information and the strategy adopted at the final measurement stage. At last the obtained results are employed to investigate the possibility of performing a microscopic-macroscopic nonlocality test free from auxiliary assumptions.

Vitelli, Chiara; Spagnolo, Nicolo [Dipartimento di Fisica, Sapienza Universita di Roma, piazzale Aldo Moro 5, 00185 Roma (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, piazzale Aldo Moro 5, 00185 Roma (Italy); Sciarrino, Fabio [Dipartimento di Fisica, Sapienza Universita di Roma, piazzale Aldo Moro 5, 00185 Roma (Italy); Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche (INO-CNR), largo E. Fermi 6, I-50125 Firenze (Italy); De Martini, Francesco [Dipartimento di Fisica, Sapienza Universita di Roma, piazzale Aldo Moro 5, 00185 Roma (Italy); Accademia Nazionale dei Lincei, via della Lungara 10, I-00165 Rome (Italy)

2010-12-15

398

Spectroscopic probes of vibrationally excited molecules at chemically significant energies. Progress report, August 15, 1991--August 14, 1992  

SciTech Connect

These experiments apply multiple-laser spectroscopic techniques to investigate the bond energies, potential surface topologies, and dissociation dynamics of highly vibrationally excited molecules. Infrared-optical double resonance pumping of light atom stretch vibrations in H{sub 2}O{sub 2} and HN{sub 3} prepares reactant molecules in single rovibrational states above the unimolecular dissociation threshold on the ground potential surface, and laser induced fluorescence detection of the OH or NH fragments monitors the partitioning of energy into individual product quantum states. Product energy partitioning data from H{sub 2}O{sub 2} dissociation provide a stringent test of statistical theories as well as potential energy surface calculations. Ongoing work on HN{sub 3} seeks to determine the height of the barrier to dissociation on the singlet potential energy surface. Our most recently developed spectroscopic scheme allows the measurement of high vibrational overtone spectra of jet-cooled molecules. This approach uses CO{sub 2} laser infrared multiphoton dissociation followed by laser induced fluorescence product detection to measure weak vibrational overtone transitions in low pressure environments. Application of this scheme to record the {Delta}V{sub OH}=4 and {Delta}V{sub OH}=5 transitions of CH{sub 3}OH cooled in a supersonic free-jet demonstrates both its feasibility and its utility for simplifying high vibrational overtone spectra.

Rizzo, T.R.

1992-03-01

399

Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water-dimer III: Mixed Jacobi-valence parametrization and benchmark results for the zero point energy, vibrationally excited states, and infrared spectrum  

NASA Astrophysics Data System (ADS)

Quantum dynamical calculations are reported for the zero point energy, several low-lying vibrational states, and the infrared spectrum of the H5O2+ cation. The calculations are performed by the multiconfiguration time-dependent Hartree (MCTDH) method. A new vector parametrization based on a mixed Jacobi-valence description of the system is presented. With this parametrization the potential energy surface coupling is reduced with respect to a full Jacobi description, providing a better convergence of the n-mode representation of the potential. However, new coupling terms appear in the kinetic energy operator. These terms are derived and discussed. A mode-combination scheme based on six combined coordinates is used, and the representation of the 15-dimensional potential in terms of a six-combined mode cluster expansion including up to some 7-dimensional grids is discussed. A statistical analysis of the accuracy of the n-mode representation of the potential at all orders is performed. Benchmark, fully converged results are reported for the zero point energy, which lie within the statistical uncertainty of the reference diffusion Monte Carlo result for this system. Some low-lying vibrationally excited eigenstates are computed by block improved relaxation, illustrating the applicability of the approach to large systems. Benchmark calculations of the linear infrared spectrum are provided, and convergence with increasing size of the time-dependent basis and as a function of the order of the n-mode representation is studied. The calculations presented here make use of recent developments in the parallel version of the MCTDH code, which are briefly discussed. We also show that the infrared spectrum can be computed, to a very good approximation, within D2d symmetry, instead of the G16 symmetry used before, in which the complete rotation of one water molecule with respect to the other is allowed, thus simplifying the dynamical problem.

Vendrell, Oriol; Brill, Michael; Gatti, Fabien; Lauvergnat, David; Meyer, Hans-Dieter

2009-06-01

400

Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water-dimer III: Mixed Jacobi-valence parametrization and benchmark results for the zero point energy, vibrationally excited states, and infrared spectrum.  

PubMed

Quantum dynamical calculations are reported for the zero point energy, several low-lying vibrational states, and the infrared spectrum of the H(5)O(2)(+) cation. The calculations are performed by the multiconfiguration time-dependent Hartree (MCTDH) method. A new vector parametrization based on a mixed Jacobi-valence description of the system is presented. With this parametrization the potential energy surface coupling is reduced with respect to a full Jacobi description, providing a better convergence of the n-mode representation of the potential. However, new coupling terms appear in the kinetic energy operator. These terms are derived and discussed. A mode-combination scheme based on six combined coordinates is used, and the representation of the 15-dimensional potential in terms of a six-combined mode cluster expansion including up to some 7-dimensional grids is discussed. A statistical analysis of the accuracy of the n-mode representation of the potential at all orders is performed. Benchmark, fully converged results are reported for the zero point energy, which lie within the statistical uncertainty of the reference diffusion Monte Carlo result for this system. Some low-lying vibrationally excited eigenstates are computed by block improved relaxation, illustrating the applicability of the approach to large systems. Benchmark calculations of the linear infrared spectrum are provided, and convergence with increasing size of the time-dependent basis and as a function of the order of the n-mode representation is studied. The calculations presented here make use of recent developments in the parallel version of the MCTDH code, which are briefly discussed. We also show that the infrared spectrum can be computed, to a very good approximation, within D(2d) symmetry, instead of the G(16) symmetry used before, in which the complete rotation of one water molecule with respect to the other is allowed, thus simplifying the dynamical problem. PMID:19548725

Vendrell, Oriol; Brill, Michael; Gatti, Fabien; Lauvergnat, David; Meyer, Hans-Dieter

2009-06-21

401

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

402

The near-infrared structure and spectra of the bipolar nebulae M2-9 and AFGL 2688: The role of ultraviolet pumping and shocks in molecular hydrogen excitation  

NASA Technical Reports Server (NTRS)

High-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M2-9 and AFGL 2688. The ability to spatially and spectrally resolve the various components of the nebulae has proved to be important in determining their physical structure and characteristics. In M2-9, the lobes are found to have a double-shell structure. The inner shell is dominated by emission from hydrogen recombination lines, and the outer shell is primarily emission from H2 lines in teh 2-2.5 micron region. Analysis of H2 line ratios indicates that the H2 emission is radiatively excited. A well-resolved photodissociation region is observed in the lobes. The spectrum of the central source is dominated by H recombination lines and a strong continuum rising toward longer wavelengths consistent with a T = 795 K blackbody. Also present are lines of He I and Fe II. In contrast, the N knot and E lobe of M2-9 show little continuum emission. The N knot spectrum consists of lines of (Fe II) and hydrogen recombination lines. In AGFL 2688, the emission from the bright lobes is mainly continuum reflected from the central star. Several molecular features from C2 and CN are present. In the extreme end of the N lobe and in the E equatorial region, the emission is dominated by lines of H2 in the 2-2.5 region. The observed H2 line ratios indicate that the emission is collisionally excited, with an excitation temperature T(sub ex) approixmately = 1600 +/- 100 K.

Hora, Joseph L.; Latter, William B.

1994-01-01

403

Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction  

NASA Astrophysics Data System (ADS)

The effects of two nearly isoenergetic C-H stretching motions on the gas-phase reaction of atomic chlorine with methane are examined. First, a 1:4:9 mixture of Cl2, CH4, and He is coexpanded into a vacuum chamber. Then, either the antisymmetric stretch (?3=3019 cm-1) of CH4 is prepared by direct infrared absorption or the infrared-inactive symmetric stretch (?1=2917 cm-1) of CH4 is prepared by stimulated Raman pumping. Photolysis of Cl2 at 355 nm generates fast Cl atoms that initiate the reaction with a collision energy of 1290+/-175 cm-1 (0.16+/-0.02 eV). Finally, the nascent HCl or CH3 products are detected state-specifically via resonance enhanced multiphoton ionization and separated by mass in a time-of-flight spectrometer. We find that the rovibrational distributions and state-selected differential cross sections of the HCl and CH3 products from the two vibrationally excited reactions are nearly indistinguishable. Although Yoon et al. [J. Chem. Phys. 119, 9568 (2003)] report that the reactivities of these two different types of vibrational excitation are quite different, the present results indicate that the reactions of symmetric-stretch excited or antisymmetric-stretch excited methane with atomic chlorine follow closely related product pathways. Approximately 37% of the reaction products are formed in HCl(v=1,J) states with little rotational excitation. At low J states these products are sharply forward scattered, but become almost equally forward and backward scattered at higher J states. The remaining reaction products are formed in HCl(v=0,J) and have more rotational excitation. The HCl(v=0,J) products are predominantly back and side scattered. Measurements of the CH3 products indicate production of a non-negligible amount of umbrella bend excited methyl radicals primarily in coincidence with the HCl(v=0,J) products. The data are consistent with a model in which the impact parameter governs the scattering dynamics.

Bechtel, Hans A.; Camden, Jon P.; Brown, Davida J. Ankeny; Zare, Richard N.

2004-03-01

404

Multiphoton adiabatic population transfer in Rydberg atoms: Classical versus Quantum picture  

Microsoft Academic Search

Coherent population transfer in Rydberg atoms by multiphoton Adiabatic Rapid Passage (ARP) has recently been experimentally realized by Maeda et al [prl 96, 073002 (2006)]. In this process, only one single multiphoton transition is required to coherently transfer population, as opposed to many concurrent single photon transitions. We present results of our classical and fully three dimensional quantum mechanical simulations

Turker Topcu; Francis Robicheaux

2008-01-01

405

Strong Field Multiphoton Inversion of a Three-Level System Using Shaped Ultrafast Laser Pulses  

NASA Astrophysics Data System (ADS)

We demonstrate strong-field population inversion in a three-level system with single and multiphoton coupling between levels using a single shaped ultrafast laser pulse. Our interpretation of the pulse shape dependence illustrates the difference between sequential population transfer and adiabatic rapid passage in three-level systems with multiphoton coupling between levels.

Clow, Stephen D.; Trallero-Herrero, Carlos; Bergeman, Thomas; Weinacht, Thomas

2008-06-01

406

Endoscope lens with dual fields of view and resolutions for multiphoton imaging  

PubMed Central

We report the development of a miniaturized dual-optical-zone endoscope objective lens. The lens has two foci, with 0.18 and 0.50 NAs. We demonstrate multiphoton imaging with dual fields of view and resolutions using the new lens. A combination of multiphoton and single-photon microscopic imaging is also demonstrated.

Chen, Minghan; Xu, Chris; Webb, Watt W.

2011-01-01

407

Real-time Ca ion wave imaging in living rat cardiac muscle cells by a confocal multiphoton microscope with a microlens-pinhole array scanner  

NASA Astrophysics Data System (ADS)

A real-time confocal multiphoton fluorescence microscope was developed to observe Ca2+ dynamics in living rat- cardiac muscle cells. The real-time imaging was achieved by multifocus excitation of a specimen with a rotating microlens-array disk. A pinhole-array disk for confocal detection was introduced in the microscope to improve the spatial resolution and the contrast of fluorescence images. Ca2+ wave and Ca2+ transient in cultured rat- cardiac cells were successfully observed with the developed microscope.

Fujita, Katsumasa; Kaneko, Tomoyuki; Nakamura, Osamu; Oyamada, Masato; Takamatsu, Tetsuro; Kawata, Satoshi

2000-04-01

408

High-resolution infrared and microwave study of 10BF2OH and 11BF2OH: the 51, 61, 71, 81, 91 and 8191 vibrationally excited states  

NASA Astrophysics Data System (ADS)

High-resolution (?2.4×10-3 cm-1) Fourier transform infrared spectra of gas-phase 10B-enriched isotopic and natural samples of BF2OH (difluoroboric acid) were recorded in the 400-4000 cm-1 spectral range. Starting from the results of a previous study [COLLET, D., PERRIN, A., BÜRGER, H., and FLAUD, J.-M., 2002, J. Molec. Spectrosc. 212, 118], which involved the ?8 (BF2 out-of-plane bending) and ?9 (OH torsion) bands of 11BF2OH, it has been possible to perform the first rovibrational analysis of the ?5 (BF2 bending), ?8, ?9 and ?8+?9 bands of 10BF2OH, and of the ?7 (F2BO in-plane bending), ?5, and ?8+?9 bands of 11BF2OH up to very high rotational quantum numbers. In addition, microwave transitions within the 51, 61, 71 and 81 vibrational states of 11BF2OH were measured using predictions from ab initio calculations [BREIDUNG, J., DEMAISON, J., D'EU, J.-F., MARGULÈS, L., COLLET, D., MKADMI, E. B., PERRIN, A., and THIEL, W., 2004, J. Mol. Spectrosc. (in press)]. The ?5, ?8, ?9 and ?8+?9 bands of 10BF2OH and the ?8+?9 band of 11BF2OH are not significantly affected by perturbations, and the experimental 51, 81 and 91 of 10BF2OH and the 8191 energy levels of 10BF2OH and 11BF2OH could be reproduced using a simple Watson-type Hamiltonian. For the ?5 and ?7 bands of 11BF2OH, C-type Coriolis interactions coupling the 51 and 71 energy levels with those of the 72 and 61 dark states, respectively, were accounted for in the calculation. In addition, an updated set of rotational parameters was provided for the unperturbed 81 and 91 vibrational states of 11BF2OH using the data from our previous analysis. In all these cases, the upper state parameters derived in this work enabled the reproduction of both the infrared and microwave data to within experimental uncertainties.

Perrin, A.; Carvajal-Zaera, M.; Dutkiewicz, Z.; Flaud, J.-M.; Collet, D.; Bürger, H.; Demaison, J.; Willaert, F.; Mäder, H.; Larsen, N. W.

409

Integrated coherent anti-Stokes Raman scattering and multiphoton microscopy for biomolecular imaging using spectral filtering of a femtosecond laser  

NASA Astrophysics Data System (ADS)

We report on a unique implementation of a dual 4-f paired-gratings spectral filtering of a femtosecond (fs) laser to realize high contrast coherent anti-Stokes Raman scattering (CARS) microscopy and high quality multiphoton microscopy on the same platform for label-free biomolecular imaging. The 4-f gratings filtering enables readily conversion of the 100 fs laser pulse trains into transform-limited 1 picosecond (ps) pulses in the spectral range of 700-1600 nm for CARS imaging. Compared with fs-CARS microscopy, our ps-CARS imaging yields an approximately tenfold improvement in spectral resolution, while a twofold improvement in nonresonant background suppression. High quality second-harmonic generation and two-photon excitation fluorescence imaging can also be acquired in tandem when swapping the 4-f grating filtering from the ps mode to fs mode. We demonstrate this multimodal nonlinear optical microscopy technique by imaging 465 nm polystyrene beads in water and animal liver tissue.

Lu, Fake; Zheng, Wei; Lin, Jian; Huang, Zhiwei

2010-03-01

410

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

411

Snapshot coherence-gated direct wavefront sensing for multi-photon microscopy.  

PubMed

Deep imaging in turbid media such as biological tissue is chall