Note: This page contains sample records for the topic infrared multiphoton excitation from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Photophysics of infrared multiphoton excitation in thiophosgene  

SciTech Connect

IR multiphoton absorption (IRMPA) in thiophosgene has been studied by IR-visible double resonance. In particular, the probability of absorption has been measured in both collision-free (molecular beam) and collision-perturbed environments by monitoring the depopulation of the ground state level (000000). Although no evidence for true multiphoton absorption is found, a number of important observations have been made. (1) No correlation exists between the IRMPA spectrum under collision-free conditions and the low energy IR absorption spectrum. (2) Homogeneous depletion of rotational populations occurs at all CO/sub 2/-laser frequencies. (3) Bottlenecks to absorption do not occur in the pumped-mode ladder. (4) The probability of absorption depends inversely on pressure and is affected dramatically by long-range collisions. These results are interpreted in the framework of an optical Bloch equation model.

Brenner, D.M.; Spencer, M.N.; Steinfeld, J.I.

1983-01-01

2

Multiphoton fluorescence excitation in continuous-wave infrared optical traps  

SciTech Connect

The multiphoton fluorescence excitation observed in a continuous-wave (cw) single-beam gradient force optical trap (optical tweezers) is reported for latex beads labeled with a yellow-green fluorescent dye (BODIPY). The fluorescence emission spectra of the yellow-green beads trapped and excited by the same 1064-nm laser light are identical to the spectra excited by the 365-nm UV light. The influence of the numerical aperture of the objective on the slope of the log{endash}log power-dependence has been demonstrated for BODIPY{endash}Oil solution under cw and pulsed-laser conditions. The possibility that three-photon excitation process occurs is discussed within the context of a dog-bone saturation model. Other possibilities for the observed fluorescence excitation have been discussed. {copyright} 1998 Optical Society of America

Zhang, Z.; Sonek, G.J.; Liang, H.; Berns, M.W.; Tromberg, B.J. [University of California, Irvine, Irvine, California 92717-0001 (United States)

1998-05-01

3

Multiphoton-Excited Serotonin Photochemistry  

Microsoft Academic Search

We report photochemical and photophysical studies of a multiphoton-excited reaction of serotonin that previously has been shown to generate a photoproduct capable of emitting broadly in the visible spectral region. The current studies demonstrate that absorption of near-infrared light by an intermediate state prepared via three-photon absorption enhances the photoproduct formation yield, with the largest action cross sections (?10?19 cm2)

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

2004-01-01

4

Multiphoton-Excited Serotonin Photochemistry  

PubMed Central

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

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

2004-01-01

5

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

6

Multi-photon excitation microscopy  

Microsoft Academic Search

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

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

2006-01-01

7

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

8

Multi-photon excitation microscopy.  

PubMed

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

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

2006-06-06

9

Infrared multiphoton dissociation of UF6  

Microsoft Academic Search

Infrared multiphoton dissociation of UF6 has been demonstrated with a 16mum CF4 laser. The process has been detected by Mie scattering from dissociated particulates and by infrared fluorescence from the HF produced in the exothermic reaction of one of the dissociation products, fluorine, with added hydrogen buffer gas. A threshold and dissociation yield similar to that reported for SF6 has

P. Rabinowitz; A. Stein; A. Kaldor

1978-01-01

10

Routes to multiphoton double ionization in combined extreme ultraviolet and infrared laser pulses  

SciTech Connect

Xenon multiphoton double ionization pathways are studied in a reaction microscope using a pump-probe arrangement of extreme ultraviolet high harmonic and infrared laser radiation. The momentum of photoelectrons is recorded in coincidence with singly or doubly charged ions. Among all possible routes to multiphoton double ionization, sequential processes using ionic excited states as intermediate steps are clearly identified.

Boettcher, M.; Rottke, H.; Zhavoronkov, N.; Sandner, W. [Max-Born-Institute, Max-Born-Strasse 2A, D-12489 Berlin (Germany); Agostini, P. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States); LIXAM (UMR 8624), Batiment 350, Centre d'Orsay, 91405 Orsay Cedex (France); Gisselbrecht, M.; Huetz, A. [LIXAM (UMR 8624), Batiment 350, Centre d'Orsay, 91405 Orsay Cedex (France)

2007-03-15

11

Infrared Multiphoton Dissociation of Three Nitrolkanes.  

National Technical Information Service (NTIS)

Infrared multiphoton dissociation in a molecular beam has been studied in order to elucidate the collision free, 'thermal' chemistry and dynamics of nitromethane, nitroethane and 2-nitropropane. The isomerization of CH3NO2 to CH3ONO was observed by detect...

A. M. Wodtke E. J. Hintsa Y. T. Lee

1986-01-01

12

Infrared multiphoton dissociation of three nitroalkanes  

SciTech Connect

Infrared multiphoton dissociation in a molecular beam has been studied in order to elucidate the collision-free thermal chemistry and dynamics of nitromethane, nitroethane, and 2-nitropropane. The isomerization of CH/sub 3/NO/sub 2/ to CH/sub 3/ONO was observed by detecting the CH/sub 3/O and NO products from the dissociation of the internally very hot, isomerized nitromethane. A novel application of RRKM theory was used to estimate the barrier height to isomerization at 55.5 kcal/mol. This method for determining barrier heights shows how a microscopic molecular beam experiment, using infrared multiphoton dissociation where the concept of temperature has no place, can be quantitatively related to pyrolysis experiments which are conducted under collisional, thermal conditions and measure phenomenological quantities such as activation energies.

Wodtke, A.M.; Hintsa, E.J.; Lee, Y.T.

1986-07-31

13

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

14

The infrared multiphoton dissociation of three nitrolkanes  

NASA Astrophysics Data System (ADS)

Infrared multiphoton dissociation in a molecular beam has been studied in order to elucidate the collision free, 'thermal' chemistry and dynamics of nitromethane, nitroethane and 2-nitropropane. The isomerization of CH3NO2 to CH3ONO was observed by detecting the CH3O and NO products from the dissociation of the very internally hot, isomerized nitromethane. A novel application of RRKM theory was used to estimate the barrier height to isomerization at 55.5 kcal/mol. The barrier height determination method was tested and found to give excellent results by applying it to the determintaion of the barrier height to HONO elimination from nitroethane, a value which is well known from activation energy measurements. The method was then applied to the case of HONO elimination from 2-nitropropane and it appears that there is good to believe that the barrier height is 3-5 kcal/mol lower in 2-nitropropane than in nitroethane. The success of this method for determining barrier heights shows how a microscopic molecular beam experiment, using infrared multiphoton dissociation where the concept of temperature has no place, can be quantitatively related to pyrolysis experiments which are conducted under collisional, thermal conditions and measure phenomenological quantities such as activation energies.

Wodtke, A. M.; Hintsa, E. J.; Lee, Y. T.

1986-01-01

15

Infrared multiphoton dissociation of unsubstituted metal carbonyls at 5 ?m  

NASA Astrophysics Data System (ADS)

A frequency-doubled carbon dioxide laser of modest output energy (1 mJ) has been used to study, for the first time, the infrared multiphoton absorption by, and dissociation of, the unsubstituted carbonyls of vanadium, chromium, iron, nickel, molybdenum, and tungsten. The multiphoton absorption cross-sections measured for Ni(CO)4, Fe(CO)5, Cr(CO)6, Mo(CO)6, and V(CO)6 are high (?𩛵0-17) and ensure facile multiphoton dissociation. In focussed beams a pressure independent reaction yield proportional to the 1.5 power of the beam energy is observed for Fe(CO)5, Cr(CO)6, and Mo(CO)6 implying threshold fluences of only 32, 25, and 26 mJ cm-2, respectively. The stoichiometry of the reaction, observed by a pressure measurement technique, is consistent with production of metal atoms and carbon monoxide as final products for Ni(CO)4, Fe(CO)5, Cr(CO)6, and Mo(CO)6. This extensive decarbonylation along the ground state surface is consistent with recent studies of the photochemistry of these molecules from excited electronic states.

Au, Mei-Kuen; Hackett, P. A.; Humphries, M.; John, P.

1984-01-01

16

Infrared multiphoton decomposition of monosilane sensitized by silicon tetrafluoride  

SciTech Connect

The decomposition of SiH/sub 4/ sensitized by the multiphoton absorption of unfocussed infrared laser radiation by SiF/sub 4/, has been studied at a fluence of 0.31 J/cm/sup 2/ and over a total pressure range of 3-16 torr. In contrast to the direct infrared multiphoton induced decomposition, the only volatile products observed are H/sub 2/ and Si/sub 2/H/sub 6/ which, within experimental error, are formed in equal amounts, It is proposed that collisional energy transfer from vibrationally excited SiF/sub 4/ produces internally excited SiH/sub 4/ to form Si/sub 2/H/sub 6/. The absence of Si/sub 3/H/sub 8/ and higher silanes in the volatile products, which is characteristic of other silane decomposition studies, is attributed to the absence of SiH/sub 3/ radicals and the fact that the SiH/sub 4/ molecules attacked by SiH/sub 2/ contain only that excess vibrational energy characteristic of thermal equilibrium at 300 K.

Longeway, P.A.; Lampe, F.W.

1983-01-20

17

Infrared Multiphoton Ignition and Enhancement of Combustion; Final Report,  

National Technical Information Service (NTIS)

The research demonstrated the feasibility of obtaining reliable ignition and enhancement of combustion by a novel concept, Infrared Multiphoton Absorption/Dissociation (IRMPA/IRMPD). A methanol-oxygen system was chosen to test this concept because methano...

M. Lavid A. T. Poulos

1986-01-01

18

Experimental Studies of Population Distributions Produced by Infrared Multiphoton Absorption.  

National Technical Information Service (NTIS)

Populations of vibrationally excited 1,1,2-trifluoroethane molecules have been prepared using a CO2 laser. The characteristics of the populations are being investigated through the use of three experimental techniques: collision-free multiphoton dissociat...

T. C. Brown K. D. King J. M. Zellweger J. R. Barker

1984-01-01

19

Photoionization of excited molecular states using multiphoton excitation techniques  

SciTech Connect

Photoelectron spectra are reported for three photon resonant, four photon ionization of H/sub 2/ via the B /sup 1/..sigma../sub u//sup +/, v = 7 (J = 2,4) and C /sup 1/..pi../sub u'/, v = 0-4 (J = 1) levels and of N/sub 2/ via the o/sub 3//sup 1/..pi../sub u'/, v = 1,2, b /sup 1/..pi../sub u'/, v = 3-5, and c /sup 1/..pi../sub u'/, v = 0 levels. The results reflect both the spectroscopy and the dynamics of photoionization of excited molecular states and are discussed in terms of the selection rules for photoionization and the relative probabilities of photoionization from Rydberg and valence states. In some cases, in accordance with the Franck-Condon principle, the results demonstrate that resonant multiphoton ionization through Rydberg states may be a powerful technique for the production of electronic, vibrational, and rotational state selected ions. However, in other cases, systematic departures from Franck-Condon factors are observed, which reflect the more subtle dynamics of excited state photoionization. 23 references, 6 figures, 2 tables.

Dehmer, P.M.; Pratt, S.T.; Dehmer, J.L.

1984-01-01

20

Multiphoton excitation as a probe for biological fractionations  

Microsoft Academic Search

In this review of our work, we describe the application of multiphoton-excited fluorescence as a detection strategy for biological molecules fractionated in micrometer-diameter electrophoresis channels. By tightly focusing a modelocked titanium:sapphire laser beam at the outlet of such channels, spectroscopically similar components can be differentiated in analysis times that range from milliseconds to minutes. Moreover, the ability to excite different

Jason B. Shear; Michael L. Gostkowski; Mary J. Gordon; Eric Okerberg; Theodore E. Curey; J. B. McDoniel; Tai-Jong Kang; David A. Vanden Bout

2001-01-01

21

Infrared multiphoton ignition and enhancement of combustion. Final report  

SciTech Connect

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

Lavid, M.; Poulos, A.T.

1986-08-01

22

Confocal multipoint multiphoton excitation microscope with microlens and pinhole arrays  

Microsoft Academic Search

We show the first experimental results with a confocal multipoint multiphoton excitation microscope, where a confocal pinhole-array is used to enhance the three-dimensional spatial resolution and the depth-penetration property. Comparisons of images obtained with and without the pinhole-array show the enhancement of the contrast of fluorescence images and the sharper depth-discrimination property in the confocal system. In the experimental result,

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

2000-01-01

23

Excitation-wavelength dependence of multiphoton excitation of fluorophores of human skin in vivo  

NASA Astrophysics Data System (ADS)

We present in vivo measurements of the excitation-wavelength dependence of the autofluorescence of major endogenous fluorophores of human skin with a multiphoton tomograph. For the investigation high-resolution multiphoton images at different depths inside the skin were recorded and the main fluorophores identified. In particular, for the autofluorescence of the fluorophores keratin, NAD(P)H, elastin and for the second-harmonic-generation light induced by collagen fibers clear trends are shown.

Breunig, Hans Georg; Studier, Hauke; K鰊ig, Karsten

2010-02-01

24

Individual bioaerosol particle discrimination by multi-photon excited fluorescence.  

PubMed

Femtosecond laser induced multi-photon excited fluorescence (MPEF) from individual airborne particles is tested for the first time for discriminating bioaerosols. The fluorescence spectra, analysed in 32 channels, exhibit a composite character originating from simultaneous two-photon and three-photon excitation at 790 nm. Simulants of bacteria aggregates (clusters of dyed polystyrene microspheres) and different pollen particles (Ragweed, Pecan, Mulberry) are clearly discriminated by their MPEF spectra. This demonstration experiment opens the way to more sophisticated spectroscopic schemes like pump-probe and coherent control. PMID:22109478

Kiselev, Denis; Bonacina, Luigi; Wolf, Jean-Pierre

2011-11-21

25

Multi-photon optical excitation of positronium  

SciTech Connect

We have performed the first resonant excitation of high n states of positronium using two resonantly excited transitions 1S to 2P and 2P to nL. Magnetic and electric fields in the chamber mixed the high n states so that all 1 sublevels were populated in the high n state. Values for the line centroid and widths were quantitatively determined and compared well with calculated predictions. Qualitative reproduction of the n{sub {minus}3} scaling of the relative transition rates was also observed.

Howell, R.H.; Ziock, K.P.; Magnotta, F.; Dermer, C.D.; Failor, R.A. (Lawrence Livermore National Lab., CA (United States)); Jones, K.M. (Williams Coll., Williamstown, MA (United States))

1991-08-20

26

vuv fluorescence from selective high-order multiphoton excitation of N{sub 2}  

SciTech Connect

Recent fluorescence studies suggest that ultrashort pulse laser excitation may be highly selective. Selective high-intensity laser excitation holds important consequences for the physics of multiphoton processes. To establish the extent of this selectivity, we performed a detailed comparative study of the vacuum ultraviolet fluorescence resulting from the interaction of N{sub 2} and Ar with high-intensity infrared ultrashort laser pulses. Both N{sub 2} and Ar reveal two classes of transitions, inner-valence ns <- np and Rydberg np <- n{sup '}l{sup '}. From their pressure dependence, we associate each transition with either plasma or direct laser excitation. Furthermore, we qualitatively confirm such associations with the time dependence of the fluorescence signal. Remarkably, only N{sub 2} presents evidence of direct laser excitation. This direct excitation produces ionic nitrogen fragments with inner-valence (2s) holes, two unidentified transitions, and one molecular transition, the N{sub 2}{sup +}:X {sup 2}{sigma}{sub g}{sup +} <- C {sup 2}{sigma}{sub u}{sup +}. We discuss these results in the light of a recently proposed model for multiphoton excitation.

Coffee, Ryan N.; Gibson, George N. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

2004-05-01

27

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

28

All-solid-state ultrafast lasers facilitate multiphoton excitation fluorescence imaging  

Microsoft Academic Search

Improvements in ultrafast laser technology have enabled a new excitation mode for optical sectioning fluorescence microscopy: multiphoton excitation fluorescence imaging. The primary advantages of this technique over laser scanning confocal imaging derive from the localized excitation volume; additional advantages accrue from the longer wavelength of the excitation source. Recent advances in all-solid-state, ultrafast (subpicosecond) laser technology should allow the technique

David L. Wokosin; Victoria Centonze; John G. White; David Armstrong; Gordon Robertson; Allister I. Ferguson

1996-01-01

29

Multiphoton excitation in a ?-type three-level system with generally nondegenerate excited states  

NASA Astrophysics Data System (ADS)

A study of multiphoton excitation in ?-type three level system with generally non-degenerate excited states is presented. Such systems are formed by the three lowest states in, e.g., hydrogen atom or evenly charged homonuclear diatomic molecular ions under moderate laser intensities. A unitary transformation is introduced for such system and the transformed Hamiltonian is simplified using Fourier-Bessel expansion. Specifically we considered the case of one dimensional model of evenly charged homonuclear diatomic molecular ion A24+ (A = nitrogen, oxygen or iodine). The obtained results indicate that such approximation is in a good agreement with exact numerical results.

Popovi?, Du歬a B.; Menda, Istok P.

2012-05-01

30

Multiphoton fluorescence excitation: new spectral windows for biological nonlinear microscopy.  

PubMed Central

Intrinsic, three-dimensionally resolved, microscopic imaging of dynamical structures and biochemical processes in living preparations has been realized by nonlinear laser scanning fluorescence microscopy. The search for useful two-photon and three-photon excitation spectra, motivated by the emergence of nonlinear microscopy as a powerful biophysical instrument, has now discovered a virtual artist's palette of chemical indicators, fluorescent markers, and native biological fluorophores, including NADH, flavins, and green fluorescent proteins, that are applicable to living biological preparations. More than 25 two-photon excitation spectra of ultraviolet and visible absorbing molecules reveal useful cross sections, some conveniently blue-shifted, for near-infrared absorption. Measurements of three-photon fluorophore excitation spectra now define alternative windows at relatively benign wavelengths to excite deeper ultraviolet fluorophores. The inherent optical sectioning capability of nonlinear excitation provides three-dimensional resolution for imaging and avoids out-of-focus background and photodamage. Here, the measured nonlinear excitation spectra and their photophysical characteristics that empower nonlinear laser microscopy for biological imaging are described. Images Fig. 1 Fig. 5 Fig. 7

Xu, C; Zipfel, W; Shear, J B; Williams, R M; Webb, W W

1996-01-01

31

Competing pathways in the infrared multiphoton dissociation of hexafluoropropene  

SciTech Connect

The infrared multiphoton dissociation of hexafluoropropene was studied by photofragment translational spectroscopy. Two primary channels and one secondary channel were identified. The predominant primary channel produces CF{sub 3}CF or C{sub 2}F{sub 4} and CF{sub 2}, with the heavier species undergoing further dissociation to two CF{sub 2} fragments. A number of dissociation mechanisms are proposed for the elimination of CF{sub 2}, including direct cleavage of the carbon-carbon double bond. In the second primary channel, a simple bond rupture reaction produces CF{sub 3} and C{sub 2}F{sub 3}. As expected, the translational energy distribution for this channel peaks near zero, indicating no exit barrier is present. The activation energy for this simple bond rupture is estimated to be 100-105 kcal/mol. The branching ratio, [CF{sub 2}]/[CF{sub 3}], between the two primary pathways is 4.0 {+-} 1.0. 38 refs., 7 figs., 1 tab.

Longfellow, C.A.; Smoliar, L.A.; Lee, Y.T. [Lawrence Berkeley Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States); Lee, Y.R.; Yeh, C.Y.; Lin, S.M. [Inst. of Atomic and Molecular Sciences, Taipei (Taiwan, Province of China)

1997-01-23

32

Infrared multiphoton decomposition of phosphine sensitized by silicon tetrafluoride  

SciTech Connect

The decomposition of PH/sub 3/, sensitized by the multiphoton absorption of unfocussed infrared laser radiation by SiF/sub 4/, has been studied in the fluence range of 0.2-0.6 J/cm/sup 2/ and over a total pressure range of 1-16 torr. Absorption of radiation at 1025.3 cm/sup -1/ results in the formation of H/sub 2/ and a solid deposit which is probably composed of polymeric phosphorus hydrides of formula (PH)/sub x/. No significant amount of gaseous phosphorus compounds were detected, although it is possible that trace amounts of P/sub 2/(g) were formed. The effects of initial composition, pressure, fluence, and presence of foreign gases (He, N/sub 2/) on the yields of PH/sub 3/ decomposition and H/sub 2/ formation were examined. A mechanism is proposed which involves absorption of laser energy by SiF/sub 4/, followed by collisional energy transfer to PH/sub 3/ and subsequent unimolecular decomposition of PH/sub 3/ to PH and H/sub 2/. The mechanism is shown to be in reasonable accord with the experimental data.

Blazejowski, J.; Lampe, F.W.

1984-04-12

33

Infrared multiphoton dissociation with a hollow fiber waveguide.  

PubMed

A novel scheme for performing infrared multiphoton dissociation (IRMPD) is presented in which a hollow fiber waveguide (HFWG) is used to transmit IR radiation into the ion storage region of a mass spectrometer. Efficient dissociation of oligonucleotide and protein ions is demonstrated on an ESI-FTICR instrument in which IRMPD is performed in the external ion reservoir and on a quadrupole ion trap. Using a simple optical scheme consisting of a single focusing lens and an x, y translator, the 10.6-microm IR laser beam, initially 3.5 mm in diameter, is focused into the vacuum-sealed HFWG. The small internal diameter and the high transfer efficiency of the waveguide allow IR radiation of high power density to be employed for IRMPD. In studies performed on a quadrupole ion trap, a 500-microm-i.d. waveguide was used as a medium to transmit IR radiation directly through a 700-microm orifice in the ring electrode. Efficient IRMPD of both a 12-mer oligonucleotide and the protein melittin were performed at laser powers of 0.5 and 3.2 W, respectively. PMID:14572028

Drader, Jared J; Hannis, James C; Hofstadler, Steven A

2003-08-01

34

Rotational state distribution of HCl formed in the infrared multiphoton dissociation of trichloroethene  

Microsoft Academic Search

The rotational state distributions of HCl(v = 0 and 1) formed in the infrared multiphoton dissociation of trichloroethene have been measured by employing the (2+1) resonantly enhanced multiphoton ionization technique combined with time-of-flight mass spectrometry. The distributions could be well reproduced by Boltzmann distributions. The rotational temperatures were determined to be 910100 and 490160 K for v = 0 and

Kei Sato; Shigeru Tsunashima; Toshiyuki Takayanagi; Ginji Fujisawa; Atsushi Yokoyama

1995-01-01

35

Lie algebraic approach to multiphoton excitation of diatomic molecules in intense laser fields  

SciTech Connect

The quadratic anharmonic oscillator Lie algebraic model is used to study the multiphoton transition of the diatomic molecule placed in intense laser fields. The multiphoton excitation of vibration and vibration-rotation of diatomic molecules in intense laser fields are discussed. In the pure vibration transition they calculate the transition probability versus the frequency of the laser fields for the CO molecule. They also investigate the roles of rotational motion in multiphoton processes and compare with pure vibration for the LiH molecule. The influences of the angular quantum number l and the molecular orientations in laser fields on the multiphoton processes are discussed. The averaged absorb energy changing with the laser field`s frequency is calculated.

Dai, Y.; Ding, S.L. [Shandong Univ., Jinan (China). Dept. of Chemistry

1999-01-20

36

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

37

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

38

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

39

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杤on 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

40

Enhancement of the selectivity and yield in infrared multiphoton dissociation of molecules in multifrequency infrared laser fields  

SciTech Connect

Methods of increasing the yield and selectivity of infrared multiphoton dissociation of molecules in multifrequency infrared laser fields are examined. A simple method of obtaining multifrequency lasing using a single CO/sub 2/ laser is proposed and implemented. The multifrequency radiation obtained is used for separation of /sup 13/C//sup 12/C isotopes by multiphoton dissociation of CF/sub 2/HCl molecules. A selectivity Sapprox.10/sup 4/ and a dissociation yield of /sup 13/CF/sub 2/HCl molecules /sup 13/..beta..roughly-equal1% were achieved. For S = 10/sup 2/ the yield was /sup 13/..beta..roughly-equal45%. The total laser energy densities required were reduced.

Evseev, A.V.; Puretskii, A.A.

1985-05-01

41

Photodissociation and photoionization of pyrrole following the multiphoton excitation at 243 and 364.7 nm.  

PubMed

Photoelectron imaging and time of flight mass spectrometry are used to study the multiphoton ionization and dissociation of pyrrole and its cation following excitation at 243 nm and at 364.7 nm. Our results confirm the 8.2 eV ionization potential of pyrrole and the 9.2 eV ionization threshold for forming the 2B1 first excited state of the cation. Prompt photolysis of the N-H bond in neutral pyrrole following one-photon excitation to its 1 1A2 neutral excited state is inferred from analysis of the two-photon photoelectron spectrum recorded at 243 nm, confirming the findings of recent translational spectroscopy studies. Facile dissociation of the pyrrole cation is also observed following excitation at 243 nm; analysis of the fragment cations indicates the operation of a complex dissociation mechanism involving dual bond fission and possible migration of the H atom originally bonded to the nitrogen heteroatom. PMID:19791378

van den Brom, Alrik J; Kapelios, Makis; Kitsopoulos, Theofanis N; Nahler, N Hendrik; Cronin, Br韉; Ashfold, Michael N R

2005-03-01

42

Effect of laser pulse shape on multiphoton excitation of a polyatomic molecule  

NASA Astrophysics Data System (ADS)

The influence of the laser pulse shape on the multiple photon excitation dynamics of a large molecule like 0953-4075/29/23/016/img1 has been studied numerically in the pico- and nanosecond scale. In the theoretical model used multiphoton excitations are described in terms of the optical Bloch equations for the density matrix of four anharmonically shifted discrete vibrational levels coupled by the laser field and undergoing irreversible loss from the topmost level to the quasicontinuum (QC). The excitation in the QC is described by rate equations with loss from the discrete region as input. These equations are solved using the Monte Carlo technique suitably modified for a sharply varying laser intensity profile. The results show that the excitation of the QC and absorption due to a shaped laser pulse is greater than the corresponding quantities for a constant-intensity pulse of the same frequency, fluence and duration around the fundamental. The differences are small when the discrete-level bottleneck is very low (e.g. at the three-photon resonance frequency) or very high (e.g. when the frequency is blue shifted from the fundamental). The time dependence of multiphoton absorption (MPA) and temporal distribution of excited populations, is modified greatly by the pulse shape. The energy distributions of populations in the QC at different times, however, are not affected very much.

Mitra, S. S.; Bhattacharyya, S. S.

1996-12-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2002-04-01

44

Functional patterned multiphoton excitation deep inside scattering tissue  

NASA Astrophysics Data System (ADS)

Stochastic distortion of light beams in scattering samples makes in-depth photoexcitation in brain tissue a major challenge. A common solution for overcoming scattering involves adaptive pre-compensation of the unknown distortion. However, this requires long iterative searches for sample-specific optimized corrections, which is a problem when applied to optical neurostimulation where typical timescales in the system are in the millisecond range. Thus, photoexcitation in scattering media that is independent of the properties of a specific sample would be an ideal solution. Here, we show that temporally focused two-photon excitation with generalized phase contrast enables photoexcitation of arbitrary spatial patterns within turbid tissues with remarkable robustness to scattering. We demonstrate three-dimensional confinement of tailored photoexcitation patterns >200 祄 in depth, both in numerical simulations and through brain slices combined with patch-clamp recording of photoactivated channelrhodopsin-2.

Papagiakoumou, Eirini; B鑗ue, Aur閘ien; Leshem, Ben; Schwartz, Osip; Stell, Brandon M.; Bradley, Jonathan; Oron, Dan; Emiliani, Valentina

2013-04-01

45

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

46

Multi-photon excitation microscopy in intact animals  

PubMed Central

Two-photon excitation fluorescence microscopy (TPEFM) and backscattered-second harmonic generation (B-SHG) microscopy permit the investigation of the subcellular events within living animals, but numerous aspects of these experiments need to be optimized to overcome the traditional microscope geometry, motion, and optical coupling to the subject. This report describes a stable system for supporting a living instrumented mouse or rabbit during endogenous reduced nicotinamide adenine dinucleotide (NAD(P)H) and exogenous dye TPEFM measurements and B-SHG microscopy measurements. The system was a modified inverted Zeiss LSM510 microscope with a rotating periscope that converted the inverted scope in to an upright format, with the objective approximately 15 cm displaced from the center of the microscope base, allowing the easy placement of an instrumented animal. An Olympus 20x water immersion objective was optically coupled to the tissue, with out a cover glass, via a saline bath or custom hydrated transparent gel. The instrumented animals were held on a specially designed holder that poised the animal under the objective as well as permitted different ventilation schemes to minimize motion. Using this approach, quality images were routinely collected in living animals from both the peripheral and body cavity organs. The remaining most significant issue for physiological studies using this approach is motion on the micron scale. Several strategies for motion compensation are described and discussed.

Rothstein, Emily C.; Nauman, Michael; Chesnick, Scott; Balaban, Robert S.

2006-01-01

47

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

2008-12-05

48

The ultrafast nonlinear optical response and multi-photon absorption of a new metal complex in the near-infrared spectral range  

NASA Astrophysics Data System (ADS)

A new coordination compound, chloro(1,10-phenanthroline-N, N')(triphenylphosphine)copper(I) dichloromethane, incorporated in poly(methyl methacrylate) exhibits superior nonlinear optical properties in the near-infrared spectral region. Its nonlinear response time and third-order nonlinear optical susceptibility at 800 nm are <= 90 fs and 1.8 10 - 10 esu, respectively. Considerable nonlinear absorption is observed with this sample, near 800 and 1250 nm. The contribution of the excited states to the total nonlinear absorption process is discussed. The results reveal the potential of this newly designed compound for multi-photon absorption-based photonic applications.

Kiran, A. J.; Lee, H. W.; Sampath Kumar, H. C.; Rudresha, B. J.; Bhat, B. R.; Yeom, D.-I.; Kim, K.; Rotermund, F.

2010-03-01

49

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

PubMed Central

Background Multiphoton microscopy (MPM) offers many advantages over conventional wide-field and confocal laser scanning microscopy (CLSM) for imaging biological samples such as 3D resolution of excitation, reduced phototoxicity, and deeper tissue imaging. However, adapting MPM for critical multi-color measurements presents a challenge because of the largely overlapping two-photon absorption (TPA) peaks of common biological fluorophores. Currently, most multi-color MPM relies on the absorbance at one intermediate wavelength of multiple dyes, which introduces problems such as decreased and unequal excitation efficiency across the set of dyes. Results Here we describe an MPM system incorporating two, independently controlled sources of two-photon excitation whose wavelengths are adjusted to maximally excite one dye while minimally exciting the other. We report increased signal-to-noise ratios and decreased false positive emission bleed-through using this novel multiple-excitation MPM (ME-MPM) compared to conventional single-excitation MPM (SE-MPM) in a variety of multi-color imaging applications. Conclusions Similar to the tremendous gain in popularity of CLSM after the introduction of multi-color imaging, we anticipate that the ME-MPM system will further increase the popularity of MPM. In addition, ME-MPM provides an excellent tool to more rapidly design and optimize pairs of fluorescence probes for multi-color two-photon imaging, such as CFP/YFP or GFP/DsRed for CLSM.

2011-01-01

50

Exceptionally strong multiphoton-excited blue photoluminescence and lasing from ladder-type oligo(p-phenylene)s.  

PubMed

We report the synthesis and investigation of multiphoton absorption properties of a novel series of diphenylamino-end-capped ladder-type oligo(p-phenylene)s which exhibit greatly enhanced and efficient multiphoton (from two- to five-photon) upconverted blue photoluminescence with which the record-high intrinsic three-photon absorption cross-section of 4.56 10(-76) cm(6) s(2) in the femtosecond regime has been obtained. Exceptionally efficient two- to five-photon-excited lasing in the blue region has also been demonstrated in which the highest two-photon-excited lasing efficiency of 0.34% has been achieved. PMID:22519510

Fan, Hai Hua; Guo, Lei; Li, King Fai; Wong, Man Shing; Cheah, Kok Wai

2012-04-24

51

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

NASA Astrophysics Data System (ADS)

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

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

2002-06-01

52

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

53

Multiphoton excitation and photodynamic activity of macromolecular derivatized mTHPC  

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

54

Multiphoton endoscopy  

NASA Astrophysics Data System (ADS)

Despite widespread use of multiphoton fluorescence microscopy, development of endoscopes for nonlinear optical imaging has been stymied by the degradation of ultrashort excitation pulses that occurs within optical fiber as a result of the combined effects of group-velocity dispersion and self-phase modulation. We introduce microendoscopes (350-1000 ?m in diameter) based on gradient-index microlenses that effectively eliminate self-phase modulation within the endoscope. Laser-scanning multiphoton fluorescence endoscopy exhibits micrometer-scale resolution. We used multiphoton endoscopes to image fluorescently labeled neurons and dendrites.

Jung, Juergen C.; Schnitzer, Mark J.

2003-06-01

55

Attenuation of molecular function by multiphoton excitation-evoked chromophore-assisted laser inactivation (MP-CALI) using green fluorescent protein  

NASA Astrophysics Data System (ADS)

Noninvasive and straightforward methods to inactivate selected proteins in the living cell with high spatiotemporal resolution are eagerly sought for elucidation of protein function in the post-genome-mapping era. Chromophore-assisted laser inactivation (CALI) facilitates inactivation of proteins by photochemically generated reactive oxygen species (ROS), but CALI using single-photon excitation thus far has presented several drawbacks, including its complex procedure, low efficiencies of inactivation with a certain chromophore, and photodamage effects. We here show that by application of multiphoton excitation to CALI using near-infrared femtosecond laser, enhanced green fluorescent protein (EGFP) can work as an effective chromophore for inactivation of a protein's function without nonspecific photodamage in the living cell.

Takamatsu, Tetsuro

2007-03-01

56

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

57

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

PubMed

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

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

2013-10-21

58

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

59

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 祄 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

60

REVIEW ARTICLE: Multi-photon high-excitation-energy approach to fibre grating inscription  

NASA Astrophysics Data System (ADS)

Amongst the most important and frequently used fibre devices, fibre Bragg and long-period gratings are conventionally fabricated by low-intensity (I < 107 W cm-2) UV quanta with an energy of about 5 eV, which coincides with the maximum of the absorption band of defects in germanosilicate glass (the usual material of a fibre core). Such a single-quantum photochemical technique produces refractive index changes in the fibre core and not in the fibre cladding. The use of single-quantum excitation with high-energy vacuum UV photons with 157 nm wavelength or two-quantum 193 nm excitation through the real intermediate state results in a higher excitation energy (7.9 and 12.8 eV, respectively) and significantly increases the efficiency of grating inscription. However, neither of these high-energy approaches is free of disadvantages: the 157 nm radiation is strongly absorbed by practically all optical materials and even by air; the application of the second approach is based on the existence of an intermediate state, i.e. presence of absorption at the irradiation wavelength. The new multi-photon high-excitation-energy approach to fibre grating fabrication is based on refractive index change modification by high-intensity (I ~ 1011-1013 W cm-2) femtosecond UV, near-UV or IR laser radiation applied to fibre, which acquires a total excitation energy of about 8-12 eV via two-, three- or even five-photon (through the intermediate virtual state/states) absorption processes. Such a high value of excitation energy exceeds the band-gap energy values for both the fibre core and the cladding, which could result in asymmetric light energy deposition inside the fibre and even inside the fibre core. We will consider the advantages of this novel technique such as grating fabrication in fibres of any content, including photonic crystal ones; the writing of extremely stable gratings with erasing temperatures above 1000 癈 the point-by-point inscription of Bragg gratings, including non-uniform 'chirped' ones; the creation of fibre gratings with high polarization properties; etc.

Nikogosyan, David N.

2007-01-01

61

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

62

Molecular activation with low-intensity cw infrared laser radiation. Multiphoton dissociation of ions derived from Diethyl ether  

Microsoft Academic Search

Multiphoton dissociation of gas-phase ions derived from (C釮)釵, (C釪)釵, and C釮釵C釪 using low-intensity infrared CO laser radiation is reported. Techniques of ion cyclotron resonance (ICR) spectroscopy are used to store ions, allowing irradiation for up to 2 s with intensities of 1-100 W cm-虏. Reasonably uniform irradiation of the stored ions is achieved with an unfocused laser beam facilitating studies

D. S. Bomse; R. L. Woodin; J. L. Beauchamp

1979-01-01

63

Structural and dynamical aspects of skin studied by multiphoton excitation fluorescence microscopy-based methods.  

PubMed

This mini-review reports on applications of particular multiphoton excitation microscopy-based methodologies employed in our laboratory to study skin. These approaches allow in-depth optical sectioning of the tissue, providing spatially resolved information on specific fluorescence probes' parameters. Specifically, by applying these methods, spatially resolved maps of water dipolar relaxation (generalized polarization function using the 6-lauroyl-2-(N,N-dimethylamino)naphthale probe), activity of protons (fluorescence lifetime imaging using a proton sensitive fluorescence probe - 2,7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein) and diffusion coefficients of distinct fluorescence probes (raster imaging correlation spectroscopy) can be obtained from different regions of the tissue. Comparative studies of different tissue strata, but also between equivalent regions of normal and abnormal excised skin, including applications of fluctuation correlation spectroscopy on transdermal penetration of liposomes are presented and discussed. The data from the different studies reported reveal the intrinsic heterogeneity of skin and also prove these strategies to be powerful noninvasive tools to explore structural and dynamical aspects of the tissue. PMID:23608611

Bloksgaard, Maria; Brewer, Jonathan; Bagatolli, Luis A

2013-04-19

64

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

65

High-resolution fluorescence microscopy employing a cyclic sequential multiphoton excitation  

Microsoft Academic Search

We demonstrate high-resolution fluorescence microscopy based on a cyclic sequential multiphoton process, which gives rise to fluorescence emission following a sequence of cyclic transitions between the bright and dark states of a fluorophore.

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

2010-01-01

66

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation  

NASA Astrophysics Data System (ADS)

We report wavelength- and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt free-electron laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 ?m. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multiphoton absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free-carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two- and three-photon absorption coefficients (? and ?) as fitting parameters. Using newly measured values of the low-intensity FCA cross sections, we find a best fit to the data at 2.8 ?m that is in agreement with theory and previous measurements. We report a ratio of 175 for ? across the direct-to-indirect transition, and a ratio of 5 across the same transition for ?. These ratios are independent of systematic variations in free-carrier cross sections and beam diameter.

Seo, D.; Gregory, J. M.; Feldman, L. C.; Tolk, N. H.; Cohen, P. I.

2011-05-01

67

Electron detachment dissociation and negative ion infrared multiphoton dissociation of electrosprayed intact proteins.  

PubMed

In top-down proteomics, intact gaseous proteins are fragmented in a mass spectrometer by, e.g., electron capture dissociation (ECD) to obtain structural information. By far, most top-down approaches involve dissociation of protein cations. However, in electrospray ionization of phosphoproteins, the high acidity of phosphate may contribute to the formation of intramolecular hydrogen bonds or salt bridges, which influence subsequent fragmentation behavior. Other acidic proteins or proteins with regions containing multiple acidic residues may also be affected similarly. Negative ion mode, on the other hand, may enhance deprotonation and unfolding of multiply phosphorylated or highly acidic protein regions. Here, activated ion electron detachment dissociation (AI-EDD) and negative ion infrared multiphoton dissociation (IRMPD) were employed to investigate the fragmentation of intact proteins, including multiply phosphorylated ?-casein, calmodulin, and glycosylated ribonuclease B. Compared to AI-ECD and positive ion IRMPD, AI-EDD and negative ion IRMPD provide complementary protein sequence information, particularly in regions with high acidity, including the multiply phosphorylated region of ?-casein. PMID:22175525

Song, Hangtian; H錵ansson, Kristina

2011-12-29

68

Infrared Multiphoton Dissociation of Peptide Cations in a Dual Pressure Linear Ion Trap Mass Spectrometer  

PubMed Central

A dual pressure linear ion trap mass spectrometer was modified to permit infrared multiphoton dissociation (IRMPD) in each of the two cells - the first a high pressure cell operated at nominally 5 10-3 Torr and the second a low pressure cell operated at nominally 3 10-4 Torr. When IRMPD was performed in the high pressure cell, most peptide ions did not undergo significant photodissociation; however, in the low pressure cell peptide cations were efficiently dissociated with less than 25 ms of IR irradiation regardless of charge state. IRMPD of peptide cations allowed the detection of low m/z product ions including the y1 fragments and immonium ions which are not typically observed by ion trap collision induced dissociation (CID). Photodissociation efficiencies of ~100% and MS/MS (tandem mass spectrometry) efficiencies of greater than 60% were observed for both multiply and singly protonated peptides. In general, higher sequence coverage of peptides was obtained using IRMPD over CID. Further, greater than 90% of the product ion current in the IRMPD mass spectra of doubly charged peptide ions was composed of singly charged product ions compared to the CID mass spectra in which the abundances of the multiply and singly charged product ions were equally divided. Highly charged primary product ions also underwent efficient photodissociation to yield singly charged secondary product ions, thus simplifying the IRMPD product ion mass spectra.

Gardner, Myles W.; Smith, Suncerae I.; Ledvina, Aaron R.; Madsen, James A.; Coon, Joshua J.; Schwartz, Jae C.; Stafford, George C.; Brodbelt, Jennifer S.

2009-01-01

69

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; K鰊ig, Karsten

2012-02-01

70

Isotopically selective multiphoton dissociation of CF/sub 2/HCl in collision conditions of excitation  

SciTech Connect

The effect of the energy density, laser radiation frequency, and resonance and buffer gas pressure on the process of multiphoton dissociation of CF/sub 2/HCl molecules was experimentally studied. The dependence of the threshold value of the energy density on the resonance gas pressure in long-wave tuning of the radiation frequency on the maxima of the spectra of linear and multiphoton absorption of /sup 13/CF/sub 2/HCl molecules was studied. A model which qualitatively explains the threshold character of dissociation and the increase in selectivity with an increase in the gas pressure and radiation pulse duration was proposed.

Avatkov, O.N.; Vetsko, V.M.; Dzneladze, D.I.; Esadze, G.G.; Kaminskii, A.V.; Kudziev, A.G.; Kudziev, T.A.

1988-09-01

71

Pressure and Power Dependence in the Infrared Laser Photolysis of 1-Chloro-1-Fluoroethylene: Experiment and Modeling Calculations.  

National Technical Information Service (NTIS)

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, pre...

N. S. Nogar W. A. Jalenak

1981-01-01

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

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.

K鰊ig, Karsten; Weinigel, Martin; Breunig, Hans Georg; Gregory, Axel; Fischer, Peter; Kellner-H鰂er, Marcel; B點kle, Rainer

2010-02-01

74

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

PubMed Central

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

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

2013-01-01

75

Multiphoton microscopy for cell surgery  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy is a very promising method for 3D imaging of living cells. The fluorochromes are solely excited at the laser focus by multiphoton absorption using near-infrared femtosecond laser pulses. The arising fluorescence serves for a pixel-to-pixel imaging with a resolution in the submicron range. At higher laser powers, the multiphoton absorption creates a micro plasma which induces an outwardly propagating shock wave. The rapidly expanding cavitation bubble causes disruption of the material, with hardly any interaction with the surrounding tissue as the optical breakdown proceeds faster than the thermal conduction. This combination offers the possibility of simultaneous manipulation and analysis of living cells or cell organelles. Manipulation is achieved using laser pulses with an energy of a few nanojoules while imaging is done at less than 1 nJ. The obtained resolution allows the precise cutting of single cell organelles without compromising the cells` viability. Thus, the implementation is excellently suited for cell surgery. We conducted ablation of different subcellular structures, like mitochondria, at different pulse energies within living cells while studying cell viability.

Baumgart, J.; Heisterkamp, A.; Ngezahayo, A.; Ertmer, W.; Lubatschowski, H.

2006-03-01

76

VIBRATIONALLY EXCITED HCN IN THE LUMINOUS INFRARED GALAXY NGC 4418  

SciTech Connect

Infrared pumping and its effect on the excitation of HCN molecules can be important when using rotational lines of HCN to probe dense molecular gas in galaxy nuclei. We report the first extragalactic detection of (sub)millimeter rotational lines of vibrationally excited HCN, in the dust-enshrouded nucleus of the luminous infrared galaxy NGC 4418. We estimate the excitation temperature of T{sub vib} {approx} 230 K between the vibrational ground and excited (v{sub 2} = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v{sub 2} = 1 state must have a strong impact on the rotational excitation in the vibrational ground level, although it may not be dominant for all rotational levels. Our observations also revealed nearly confusion-limited lines of CO, HCN, HCO{sup +}, H{sup 13}CN, HC{sup 15}N, CS, N{sub 2}H{sup +}, and HC{sub 3}N at {lambda} {approx} 1 mm. Their relative intensities may also be affected by the infrared pumping.

Sakamoto, Kazushi [Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan (China); Aalto, Susanne [Onsala Space Observatory, Onsala (Sweden); Evans, Aaron S. [Department of Astronomy, University of Virginia, Charlottesville, VA (United States); Wiedner, Martina C. [Observatoire de Paris, Paris (France); Wilner, David J., E-mail: ksakamoto@asiaa.sinica.edu.t [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

2010-12-20

77

Infrared multiphoton dissociation of MC釮鈡sup +} [M = Fe, Co, or Ni; C釮 = 1,3-butadiene or (C釮)(C釮)  

Microsoft Academic Search

The infrared multiphoton dissociation (IRMPD) of the two isomers, M(1,3-butadiene){sup +} and M(C釮)-(C釮){sup +} (M = Fe, Co, or Ni), was investigated. For the butadiene system, FeC釩鈡sup +} was observed to give three products, CoC釮鈡sup +} four products, and NiC釮鈡sup +} only one product. The observation of four products has not been previously seen in IRMPD studies of ions and

P. I. Surya; D. R. A. Ranatunga; B. S. Freiser

1997-01-01

78

Structural characterization of the GM1 ganglioside by infrared multiphoton dissociation, electron capture dissociation, and electron detachment dissociation electrospray ionization FT-ICR MS\\/MS  

Microsoft Academic Search

Gangliosides play important biological roles and structural characterization of both the carbohydrate and the lipid moieties\\u000a is important. The FT-ICR MS\\/MS techniques of electron capture dissociation (ECD), electron detachment dissociation (EDD),\\u000a and infrared multiphoton dissociation (IRMPD) provide extensive fragmentation of the protonated and deprotonated GM1 ganglioside.\\u000a ECD provides extensive structural information, including identification of both halves of the ceramide and

Melinda A. McFarland; Alan G. Marshall; Christopher L. Hendrickson; Carol L. Nilsson; Pam Fredman; Jan-Eric M錸sson

2005-01-01

79

Generation of electronically excited products in the multiphoton dissociation of phosgene at 193 nm  

NASA Astrophysics Data System (ADS)

Observation of electronically excited Cl2 upon dissociation of phosgene is reported. Evidence for the formation of neutral fragments arising from states embedded in the ionization continuum is discussed.

Wilson, M. W.; Rothschild, M.; Rhodes, C. K.

1983-07-01

80

Chaos in a Semiclassical Model of Multiphoton Excitation of Spherical Top Molecules.  

National Technical Information Service (NTIS)

We study the dynamical effects of vibration-rotation coupling in multiple photon excitation at lowest order. Our molecular model is the simplest possible: that of an oscillator (triply degenerate) and uncoupled rigid rotor. The molecule-field interactions...

H. W. Galbraith J. R. Ackerhalt P. W. Milonni

1983-01-01

81

Infrared light excites cells by changing their electrical capacitance  

PubMed Central

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

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

2012-01-01

82

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

2012-03-13

83

IR multiphoton excitation of SF{sub 6} molecules subliming from the surface of (CO{sub 2}){sub N} nanoparticles in a cluster beam  

SciTech Connect

This work examines IR multiphoton excitation of SF{sub 6} molecules subliming from the surface of (CO{sub 2}){sub N} van der Waals clusters (nanoparticles) in a cluster beam (the number of monomers per cluster, N{>=}10{sup 2}). The SF{sub 6} molecules are captured by clusters when a cluster beam intersects a molecular beam and sublime from the cluster surface after a certain time, carrying information about the velocity and temperature (internal energy) of the clusters. The multiphoton absorption spectra of the SF{sub 6} molecules subliming from the cluster surface are markedly narrower than those of the SF{sub 6} molecules in the parent, gas-dynamically cooled molecular beam, indicating that the vibrational temperature of the molecules subliming from the cluster surface is lower. Therefore, the proposed technique can be used to produce strongly vibrationally cooled molecules, which are of interest for a number of applications, in particular for achieving high-selectivity IR multiphoton excitation and isotopically selective dissociation of molecules. (nonlinear optical phenomena)

Makarov, Grigorii N; Petin, A N [Institute for Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow region (Russian Federation)

2009-11-30

84

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

Microsoft Academic Search

Multicolor nonlinear microscopy of living tissue using two- and three-photon-excited intrinsic fluorescence combined with second harmonic generation by supermolecular structures produces im- ages with the resolution and detail of standard histology without the use of exogenous stains. Imaging of intrinsic indicators within tissue, such as nicotinamide adenine dinucleotide, retinol, in- doleamines, and collagen provides crucial information for physi- ology and

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

2003-01-01

85

Infrared laser induced multiphoton dissociation of decafluorocyclopentane in a concerted pathway: time resolved evidence of :CF/sub 2/ formation  

SciTech Connect

The infrared multiphoton dissociation (IRMPD) of decafluorocyclopentane (DFCP) generates tetrafluoroethylene and difluorocarbene as the primary products. The :CF/sub 2/ dimerizes to form C/sub 2/F/sub 4/; the kinetics of the reaction is followed by monitoring the disappearance of :CF/sub 2/ absorption at 249 nm in real time after the CO/sub 2/ laser pulse, with a rate constant k/sub 2/ = 4.35 x 10/sup 7/ M/sup -1/ s/sup -1/. The vibrational temperature associated with the nascent :CF/sub 2/ is found to be 1100 K. The MPD yield of DFCP shows a strong fluence dependence, with a threshold of approx. 0.5 J/cm/sup 2/ for the 10 R(40) CO/sub 2/ laser line. The MPD spectra reveal two peaks, one 22 cm/sup -1/ red-shifted from the 989 cm/sup -1/ strong IR absorption band. Addition of SF/sub 6/ decreases the MPD yield.

Chowdhury, P.K.; Rama Rao, K.V.S.; Mittal, J.P.

1988-01-14

86

Chaos in semiclassical model of multiphoton excitation of spherical top molecules  

Microsoft Academic Search

The dynamical effects of vibration-rotation coupling in multiple photon excitation at lowest order using the simplest molecular model possible: that of an oscillator (triply degenerate) and uncoupled rigid rotor. The molecule-field interactions introduce a vibration-rotation nonlinearity which gives rise to nonconservation of the molecular angular momentum and in some instances consequent chaotic dynamics. The chaos leads to incoherence (widely seen

H. W. Galbraith; J. B. Ackerhalt; P. W. Milonni

1983-01-01

87

Effect of the odd-photon destructive interference on laser-induced transparency and multiphoton excitation and ionization in rubidium  

Microsoft Academic Search

We report experimental results on two-color multiphoton ionization and four-wave-mixing production under conditions where one form of laser-induced transparency (LIT) occurs. Under the conditions of LIT, multiphoton-ionization line shapes obtained by tuning one laser through a two-photon resonance exhibit a pronounced Autler-Townes splitting at low concentrations, when a second laser couples the two-photon state to a third level. In this

Lu Deng; W. R. Garrett; M. G. Payne; D. Z. Lee

1996-01-01

88

Infrared imaging results of an excited planar jet  

NASA Astrophysics Data System (ADS)

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

Farrington, R. B.

1991-12-01

89

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

90

Water splitting by infrared femtosecond laser excitation of surface plasmon  

NASA Astrophysics Data System (ADS)

Gold nanoparticles supported on soda-lime glass exhibit a photochemical water splitting activity under infrared femtosecond laser excitation. Both H2 and hydroxyl radicals productions were characterized. The hydroxyl radicals production mechanism was identified by comparison with three prototypal mechanisms, photoionization of organic compound in the UV, VUV dissociation of water and water gamma radiolysis. The mechanisms involved in the case of laser femtosecond seem to be water ionization events occurring at distance from the gold particles.

Klett, Charles; Mirica, Jean-Philippe; Hergott, Jean-Fran鏾is; Lepetit, Fabien; Renault, Jean-Philippe

2013-02-01

91

Separation and identification of structural isomers by quadrupole collision-induced dissociation-hydrogen\\/deuterium exchange-infrared multiphoton dissociation (QCID-HDX-IRMPD)  

Microsoft Academic Search

A new approach that uses a hybrid Q-FTICR instrument and combines quadrupole collision-induced dissociation, hydrogen-deuterium\\u000a exchange, and infrared multiphoton dissociation (QCID-HDX-IRMPD) has been shown to effectively separate and differentiate\\u000a isomeric fragment ion structures present at the same m\\/z. This method was used to study protonated YAGFL-OH (free acid), YAGFL-NH2 (amide), cyclic YAGFL, and YAGFL-OCH3 (methyl ester). QCID-HDX of m\\/z 552.28

Ashley C. Gucinski; 羠p醖 Somogyi; Julia Chamot-Rooke; Vicki H. Wysocki

2010-01-01

92

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. K鰊ig; A. Ehlers; F. Stracke; I. Riemann

2006-01-01

93

Versatile Photosensitizers for Photodynamic Therapy at Infrared Excitation  

PubMed Central

A new type of photosensitizers used in photodynamic therapy, which is based on photon upconverting nanoparticles, is reported. These photosensitizers are excitable with infrared irradiation, which has several times larger tissue penetration depth than the currently available ones. They are brought close to the target cancer cells through antigen-antibody interaction with good specificity and versatility. The design is also flexible in that various photosensitive molecules can be potentially adopted into the design. Results from in vitro experiments demonstrate their promise of becoming the next generation photodynamic therapy drugs.

Zhang, Peng; Steelant, Wim; Kumar, Manoj; Scholfield, Matthew

2008-01-01

94

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

PubMed Central

We present a new convenient method for quantitative three-dimensionally resolved diffusion measurements based on the photobleaching (FRAP) or photoactivation (FRAPa) of a disk-shaped area by the scanning laser beam of a multiphoton microscope. Contrary to previously reported spot-photobleaching protocols, this method has the advantage of full scalability of the size of the photobleached area and thus the range of diffusion coefficients, which can be measured conveniently. The method is compatible with low as well as high numerical aperture objective lenses, allowing us to perform quantitative diffusion measurements in three-dimensional extended samples as well as in very small volumes, such as cell nuclei. Furthermore, by photobleaching/photoactivating a large area, diffusion along the optical axis can be measured separately, which is convenient when studying anisotropic diffusion. First, we show the rigorous mathematical derivation of the model, leading to a closed-form formula describing the fluorescence recovery/redistribution phase. Next, the ability of the multiphoton FRAP method to correctly measure absolute diffusion coefficients is tested thoroughly on many test solutions of FITC-dextrans covering a wide range of diffusion coefficients. The same is done for the FRAPa method on a series of photoactivatable green fluorescent protein solutions with different viscosities. Finally, we apply the method to photoactivatable green fluorescent protein diffusing freely in the nucleus of living NIH-3T3 mouse embryo fibroblasts.

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

2008-01-01

95

Preferential cleavage of SS and CS bonds in electron detachment dissociation and infrared multiphoton dissociation of disulfide-linked peptide anions  

NASA Astrophysics Data System (ADS)

Disulfide bonds generally show only limited cleavage in positive ion mode collision activated dissociation (CAD). However, it has been demonstrated that a reverse situation exists in negative ion mode in which preferential SS and CS bond cleavage occurs. Here, we show that electron detachment dissociation (EDD) and infrared multiphoton dissociation (IRMPD) of peptide anions containing disulfide linkages also result in preferential cleavage of SS and CS bonds. Resulting products are mainly radical ions in EDD whereas IRMPD produces even-electron product ions, as expected, thereby supporting different disulfide cleavage mechanisms for these two fragmentation processes. We also show that, in EDD, the presence of tryptophan can result in abundant side chain loss (129 Da), which effectively can compete with disulfide bond cleavage.

Kalli, Anastasia; H錵ansson, Kristina

2007-05-01

96

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

Microsoft Academic Search

We present a theory for two- and three-photon excitation, optical shifting, and four-wave mixing when a first laser is tuned onto, or near, a two-photon resonance and a second much more intense laser is tuned near or on resonance between the two-photon resonance and a second excited state. When the second excited state has a dipole-allowed transition back to the

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

1998-01-01

97

New infrared photon absorption processes  

SciTech Connect

The fast ionization of atoms by very short laser pulses, and its possible suppression at extreme pulse intensities, is an active new field of investigation at present. Described is an investigation of whether past techniques for infrared laser multiphoton ionization of excited hydrogen atoms and of one-dimensional microwave ionization of highly excited hydrogen atoms can be combined and extended to address the new issues. Although technically difficult and requiring further improvement of apparatus, intense-field infrared laser experiments on excited hydrogen atoms are possible and can directly test theoretical and numerical results.

Bayfield, J.E.

1993-05-01

98

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朇ID) and infrared multiphoton dissociation (IRMPD), for large biomolecule fragmentation. A metal nanoESI emitter was used due to its resistance to heating above 250癈. This novel method for the dissociation of large biomolecular ions is termed 揾eat-assisted NS朇ID

Naoyuki Yamada; Ei-ichiro Suzuki; Kazuo Hirayama

2006-01-01

99

Highly efficient multiphoton-absorbing quadrupolar oligomers for frequency upconversion.  

PubMed

Two series of quadrupolar diphenylamino-endcapped oligofluorenes, PhN-OF(n)-NPh (n=2-5) and PhN-OF(n)-TAZ-OF(n)-NPh (n=1-4), which have an electron-withdrawing 1,2,4-triazole (TAZ) moiety as central core, with D-?-A-?-D structural motif (D=donor, A=acceptor), have been synthesized by palladium-catalyzed Suzuki cross-coupling of 9,9-dibutyl-7-(diphenylamino)-2-fluorenylboronic acid and the corresponding (1,2,4-triazole-based) aryl halide as key step. On pumping with infrared femtosecond lasers, these oligomers showed very strong multiphoton-excited blue photoluminescence. These D-?-D and D-?-A-?-D quadrupolar oligofluorenes exhibit superior three-photon absorption properties compared to the respective D-?-A counterparts with a highest three-photon absorption cross-section (?(3)) of up to 2.7210(-77) cm(6) s(2) . Despite the comparable linear and multiphoton absorption properties of the two types of quadrupolar oligomers PhN-OF(n)-NPh and PhN-OF(n)-TAZ-OF(n)-NPh, only the former exhibit remarkably intense and highly efficient multiphoton-excited frequency-upconverted deep blue lasing, which gives rise to record high lasing efficiency of 0.097% and very narrow of full width at half-maximum of the lasing spectra. Our findings suggest that quadrupolar-type molecules/oligomers are superior for multiphoton excited frequency upconverted lasing to their dipolar counterparts and also provide important guidelines to design highly efficient three-photon absorption molecules for photoluminescence and lasing applications. PMID:21264964

Feng, Xin Jiang; Wu, Po Lam; Li, King Fai; Wong, Man Shing; Cheah, Kok Wai

2011-01-24

100

The combination of multiphoton and reflected confocal microscopy for cornea imaging  

NASA Astrophysics Data System (ADS)

The purpose of this work is to demonstrate the combination of reflective confocal microscopy and multiphoton microscopy and its application in imaging cornea. The difficulty of optically imaging the highly translucent cornea has prevented the development of an effective non-invasive system for the clinical monitoring of the physiological or pathological states of corneas. In this work, we combine reflective confocal microscopy with multiphoton microscopy to demonstrate the potential of our methodology in the minimally invasive imaging of the cornea. The visible reflection signals from cornea can provide structural information of interfaces of different refractive indices while the multiphoton signals generated from the use of near infrared excitation allows deep tissue penetration and reduced photo-damage. In multiphoton imaging, the second harmonic generation (SHG) signal is used to detect collagen in the stroma of the cornea, and the reflective confocal imaging allows detection of the cellular components located in the epithelium. The combination of reflective and multiphoton imaging can be used to reveal complementary structural information of the corneal architecture.. The system is first tested on porcine eye cornea. Assessment of the result on the porcine eye will be used to evaluate the potential of the system as a technique for in vivo clinical applications.

Chen, Wei-Liang; Lo, Wen; Sun, Yen; Lin, Sung-Jan; Tan, Hsin-Yuan; Dong, Chen-Yuan

2006-03-01

101

Multiphoton microspectroscopy of biological specimens  

NASA Astrophysics Data System (ADS)

The non-linear nature of multi-photon fluorescence excitation restricts the fluorescing volume to the vicinity of the focal point. As a result, the technology has the capacity for micro- spectroscopy of biological specimen at high spatial resolution. Chloroplasts in mesophyll protoplast of Arabidopsis thaliana and maize stem sections were used to demonstrate the feasibility of multi-photon fluorescence micro-spectroscopy at subcellular compartments. Time-lapse spectral recording provides a means for studying the response of cell organelles to high intensity illumination.

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

2000-07-01

102

Multi-Photon Fluorescence Spectroscopy of Fluorescent Bio-Probes and Bio-Molecules.  

National Technical Information Service (NTIS)

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 ...

B. Lin C. Sun F. Kao P. Cheng Y. Wang

2000-01-01

103

Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics  

Microsoft Academic Search

This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing. Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration. Applicability of the proposed scheme has been experimentally validated on a carbon fiber

Ravibabu Mulaveesala; Subbarao Venkata Ghali

2011-01-01

104

Rotational Structure of a Super-Excited State of the NO Molecule Revealed by OODR-Multiphoton Laser Spectroscopy  

PubMed Central

The optical杘ptical double resonance time of flight (OODR-TOF) spectroscopy technique was employed to examine the 65 00066 500 cm1 region of the nitric oxide spectrum. In this region, we detected the following three electronic states: E 2?+ (? = 2) (Rydberg state), B 2? (? = 23) (valence state), and L 2? (? = 4) (valence state). The rotational structure analysis of an unexpected band in the red part of the spectra revealed the presence of a new super-excited 2?+ Rydberg state at ~13.3 eV, which was populated through a three-photon transition from the intermediate A 2?+ (? = 0) state. This super-excited state converges to the NO (a3?+) ionic state with electronic configuration (1?)2(2?)2(3?)2(4?)2(5?)2(1?)3(2?)1(3s?)1.

Lin, Yong-Ge; Colon-Garcia, Jorge E.; Cabrera, Carlos R.; Quinones, Edwin

2009-01-01

105

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.; Sudb, Aa. S.; Grant, E. R.; Shen, Y. R.; Lee, Y. T.

1980-05-01

106

Multiphoton molecular spectroscopy and excited-state dynamics of enhanced green fluorescent protein (EGFP): acid base specificity  

NASA Astrophysics Data System (ADS)

Green fluorescent protein (GFP), isolated from Aequorea victoria jellyfish, has been used extensively as a noninvasive intracellular pH indicator and site-specific fluorescent marker in biochemistry, cell biology, and molecular genetics. Numerous mutations, aimed at optimizing spectroscopic and thermodynamic properties of GFP, have been created for different applications. Fluorescence correlation spectroscopy (FCS) reveals that the enhanced green fluorescent protein mutant (EGFP; S65T/F64L) undergoes external proton exchange with the buffer on 45-300 ?s time scale with p Ka=5.80.1 [Proc. Natl. Acad. Sci. USA 95 (1998) 13573]. This contribution represents a comprehensive characterization of pH and excitation mode (wavelength, one and two photon (2P)) effects on the spectroscopy, excited-state dynamics, and rotational mobility of EGFP aiming at elucidating the significant electronic states of this molecular system. EGFP exhibits a large 2P action cross-section and, therefore, is well suited for intracellular imaging using 2P fluorescence microscopy.

Heikal, Ahmed A.; Hess, Samuel T.; Webb, Watt W.

2001-12-01

107

Assessment of epidermal cell viability by near infrared multi-photon microscopy following ballistic delivery of gold micro-particles  

Microsoft Academic Search

The use of gene guns in ballistically delivering DNA vaccine coated gold micro-particles to skin can potentially damage targeted cells, therefore influencing transfection efficiencies. In this paper, we assess cell death in the viable epidermis by non-invasive near infrared two-photon microscopy following micro-particle bombardment of murine skin. We show that the ballistic delivery of micro-particles to the viable epidermis can

Paul A. Raju; Nicholas McSloy; Nicholas K. Truong; Mark A. F. Kendall

2006-01-01

108

Investigating the 3.3 micron infrared fluorescence from naphthalene following ultraviolet excitation  

NASA Astrophysics Data System (ADS)

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

Williams, Richard M.; Leone, Stephen R.

1994-05-01

109

Resonant structure of the formation of doubly charged ions in multiphoton ionization of Sr atoms in the infrared spectral region  

Microsoft Academic Search

The process of forming doubly charged ions in ionization of Sr atoms by laser radiation in the frequency region of 82009100\\u000a cm?1 is studied experimentally. The resonant structure of the yield of these ions as a function of the radiation frequency is\\u000a found to be determined by the excitation of strongly perturbed states of Sr atoms.

I. I. Bondar; V. V. Suran

2000-01-01

110

Bleed-through and photobleaching correction in multiphoton FRET microscopy  

NASA Astrophysics Data System (ADS)

Fluorescence resonance energy transfer (FRET) microscopy provides a tool to visualize the protein with high spatial and temporal resolution. In multi-photon FRET microscopy one experiences considerably less photobleaching compared to one-photon excitation since the illumination is the diffraction limited spot and the excitation is infrared-pulsed laser light. Because of the spectral overlap involved in the selection of the fluorophore pair for FRET imaging, the spectral bleed-through signal in the FRET channel is unavoidable. We describe in this paper the development of dedicated software to correct the bleed-through signal due to donor and acceptor fluorophore molecules. We used living cells expressed with BFP-RFP (DsRed)-C/EBP(alpha) proteins in the nucleus. We acquired images of different combinations like donor alone, acceptor alone, and both acceptor and donor under similar conditions. We statistically evaluated the percentage of bleed-through signal from one channel to the other based on the overlap areas of the spectra. We then reconstructed the images after applying the correction. Characterization of multi-photon FRET imaging system taking into account the intensity, dwell time, concentration of fluorophore pairs, objective lens and the excitation wavelength are described in this paper.

Elangovan, Masilamani; Periasamy, Ammasi

2001-04-01

111

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

112

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

113

Near-infrared two-photon excitation of protoporphyrin IX: photodynamics and photoproduct generation.  

PubMed

The spectroscopy and photochemistry of protoporphyrin IX in ethanol and in Triton X-100 micelle solution have been examined using near-infrared two-photon excitation (TPE). TPE will allow photodynamic therapy with highly localized light dosage. We have determined that the photochemistry subsequent to TPE is very similar to that found for one-photon excitation. Moreover, the photoproducts observed possess very intense TPE fluorescence spectra, which allows their detection at low relative concentrations. PMID:11140272

Goyan, R L; Cramb, D T

2000-12-01

114

Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics.  

PubMed

This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing. Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration. Applicability of the proposed scheme has been experimentally validated on a carbon fiber reinforced plastic specimen containing flat bottom holes located at different depths. PMID:21639531

Mulaveesala, Ravibabu; Venkata Ghali, Subbarao

2011-05-01

115

Far-Infrared Emission Spectroscopy of Rovibrationaly Excited Water Vapor  

NASA Astrophysics Data System (ADS)

Water vapor transitions involving excited rov|ibrational levels have been identified in many high temperature space sources. Extensive experimental and theoretical efforts are still needed to provide more accurate databases concerning highly excited rovibrational levels. In this context, the high resolution emission spectrum of water vapor has been recorded between 50 and 600 cm-1 using a Bruker IFS 125HR Fourier transform interferometer and a continuous flow of water vapor rovibrationaly excited by an electrodless radio-frequency discharge. More than 1500 pure rotational lines were assigned within the fundamental (000) and first excited (010) vibrational states up to J=35. Rotational as well as rovibrational lines were identified for the higher lying states up to the first hexad. About 1000 pure rotational transitions within the vibrational states of the first hexad were assigned for the first time. The new data, along with a large body of high-resolution data, was fitted using the bending-rotation theoretical approach to compute line positions. In a preliminary analysis, the wavenumbers of 1511 new transitions involving the ground and (010) states were accounted for up to J=27 with a root mean square value of 0.8 10-3 cm-1. Work is still in progress and we are hoping to account for the new data at least up to the second triad. In the paper the new data will be presented and the results of the line position analysis will be given. Pirali and Vervloet, Chem. Phys. Letters 423 (2006) 376. Coudert, Wagner, Birk, Baranov, Lafferty, and Flaud, J. Mol. Spec. 251 (2008) 339. Coudert, J. Mol. Spec. 181 (1997) 246.

Martin, M.-A.; Pirali, O.; Balcon, D.; Vervloet, M.; Coudert, L. H.

2010-06-01

116

Microbeam-integrated multiphoton imaging system.  

PubMed

Multiphoton microscopy has been added to the array of imaging techniques at the endstation for the Microbeam II cell irradiator at Columbia University's Radiological Research Accelerator Facility (RARAF). This three-dimensional (3D), laser-scanning microscope functions through multiphoton excitation, providing an enhanced imaging routine during radiation experiments with tissuelike samples, such as small living animals and organisms. Studies at RARAF focus on radiation effects; hence, this multiphoton microscope was designed to observe postirradiation cellular dynamics. This multiphoton microscope was custom designed into an existing Nikon Eclipse E600-FN research fluorescence microscope on the irradiation platform. Design details and biology applications using this enhanced 3D-imaging technique at RARAF are reviewed. PMID:19123569

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

2008-12-01

117

Multiphoton spectroscopy of Rydberg states of small molecules  

SciTech Connect

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

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

1990-01-01

118

Control of molecular vibrational excitation and dissociation by chirped intense infrared laser pulses. Rotational effects  

Microsoft Academic Search

We extend our previous studies on control of dissociation and vibrational excitation of a diatomic molecule using chirped, intense, infrared laser pulses [Phys. Rev. Lett. 65, 2355 (1990)]. The present model includes molecular rotations and a realistic molecular dipole function. The results obtained from numerical integration of the time-dependent Schro╠inger equation show a considerable sensitivity of dissociation probabilities to the

Szczepan Chelkowski; Andr D. Bandrauk

1993-01-01

119

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癈 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癈. 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

120

[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

121

Resonant infrared laser materials processing at high vibrational excitation density: applications and mechanisms  

NASA Astrophysics Data System (ADS)

As laser micromachining is applied to ever smaller structures and more complex materials, the demand for greater control of the laser energy budget, in space and time, grows commensurately. Here we describe materials modification using picosecond resonant laser excitation in the mid-infrared spectral region to create spatially and temporally dense vibrational, rather than electronic, excitation. Examples include ablation of fused silica and machining of crystalline quartz; deposition of functionalized polymers on microstructures, and laser-directed transfer of proteins and nucleotides from a matrix of water ice. The experiments demonstrate that high spatial and temporal density of vibrational excitation can be achieved by ultrafast resonant infrared excitation of selected vibrational modes of these materials. In some cases, resonant infrared materials modification is far more successful than techniques based on ultraviolet excimer lasers. The laser used for most of the experiments was a tunable, high pulse-repetition frequency free-electron laser. However, a comparison of polymer deposition using a conventional nanosecond laser at a wavelength of 2.94 ?m shows that the possibility exists for transferring the concept to conventional table-top devices. Mechanistic considerations nevertheless suggest that utlrashort pulses are likely to be more useful than longer pulses for many applications. A figure of merit is proposed for self-consistent comparisons of processing efficiency among different lasers.

Haglund, Richard F., Jr.; Bubb, Daniel M.; Ermer, David R.; Hubler, G. K.; Houser, Eric J.; Horwitz, James S.; Ivanov, Borislav L.; Papantonakis, Michael R.; Ringeisen, Bradley R.; Schriver, Kenneth E.

2003-11-01

122

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

123

Studies of atmospheric molecules by multiphoton spectroscopy  

Microsoft Academic Search

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

Johnson

1991-01-01

124

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

125

Ultrafast excited state dynamics of Pt(II) chromophores bearing multiple infrared absorbers.  

PubMed

The paper reports the synthesis, structural characterization, electrochemistry, ultrafast time-resolved infrared (TRIR) and transient absorption (TA) spectroscopy associated with two independent d (8) square planar Pt(II) diimine chromophores, Pt(dnpebpy)Cl 2 ( 1) and Pt(dnpebpy)(C[triple bond]Cnaph) 2 ( 2), where dnpebpy = 4,4'-(CO 2CH 2- (t) Bu) 2-2,2'-bipyridine and CCnaph = naphthylacetylide. The neopentyl ester substitutions provided markedly improved complex solubility relative to the corresponding ethyl ester which facilitates synthetic elaboration as well as spectroscopic investigations. Following 400 nm pulsed laser excitation in CH 2Cl 2, the 23 cm (-1) red shift in the nu C=O vibrations in 1 are representative of a complex displaying a lowest charge-transfer-to-diimine (CT) excited state. The decay kinetics in 1 are composed of two time constants assigned to vibrational cooling of the (3)CT excited-state concomitant with its decay to the ground state (tau = 2.2 +/- 0.4 ps), and to cooling of the formed vibrationally hot ground electronic state (tau = 15.5 +/- 4.0 ps); we note that an assignment of the latter to a ligand field state cannot be excluded. Ultrafast TA data quantitatively support these assignments yielding an excited-state lifetime of 2.7 +/- 0.4 ps for the (3)CT excited-state of 1 and could not detect any longer-lived species. The primary intention of this study was to develop a Pt (II) complex ( 2) bearing dual infrared spectroscopic tags (C[triple bond]C attached to the metal and CO (ester) attached to the diimine ligand) to independently track the movement of charge density in different segments of the molecule following pulsed light excitation. Femtosecond laser excitation of 2 in CH 2Cl 2 at 400 nm simultaneously induces a red-shift in both the nu C=O (-30 cm (-1)) and the nu C[triple bond]C (-61 cm (-1)) vibrations. The TRIR data in 2 are consistent with a charge transfer assignment, and the significant decrease of the energy of the nu C[triple bond]C vibration suggests a considerable contribution from the acetylide ligands in the highest occupied molecular orbital. Therefore, we assign the lowest energy optical transitions in 2 as a combination of metal-to-ligand and ligand-to-ligand charge transfers. The excited-state of 2 is emissive at RT, with an emission maximum at 715 nm, quantum yield of 0.0012, and lifetime of 23 ns. PMID:18597448

Glik, Elena A; Kinayyigit, Solen; Ronayne, Kate L; Towrie, Michael; Sazanovich, Igor V; Weinstein, Julia A; Castellano, Felix N

2008-07-03

126

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

127

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

Microsoft Academic Search

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 S1 state of the dihydrogen-bonded phenol-BTMA complex is a locally excited state, in which only the phenol moiety is electronically excited. The infrared

Guang-Jiu Zhao; Ke-Li Han

2007-01-01

128

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

129

Far-infrared stimulated emission from optically excited bismuth donors in silicon  

NASA Astrophysics Data System (ADS)

Far-infrared stimulated emission from optically pumped neutral Bi donors in silicon has been obtained. Lasing with wavelengths of 52.2 and 48.6 mum from the intra-center 2pplus-or-minus[right arrow]1s(E:Gamma]8),1s(T2:[Gamma8) transitions has been realized under CO2 laser pumping. The population inversion mechanism is based on fast optical-phonon-assisted relaxation from the 2p0 and 2s excited states directly to the ground 1s(A) state leading to relatively small population in the intermediate 1s(E), 1s(T2) excited states.

Pavlov, S. G.; Hubers, H.-W.; Rummeli, M. H.; Zhukavin, R. Kh.; Orlova, E. E.; Shastin, V. N.; Riemann, H.

2002-06-01

130

Excited OH 4.7-GHz masers associated with IRAS far-infrared sources  

NASA Astrophysics Data System (ADS)

A sample of 44 sources has been searched for maser emission from excited OH in the 2Pi1/2J = 1/2 state, in the three lines at 4765, 4750 and 4660 MHz. Most of the objects searched were taken from the large sample of powerful far-infrared sources previously searched for OH 18-cm emission by Cohen, Baart and Jonas. Nine sources were detected at 4765 MHz, including two new discoveries. Three of these sources were detected at 4750 MHz, including the first strong 4750-MHz maser, and two of the sources were detected at 4660 MHz. Strong variations were observed in four previously known 4765-MHz maser sources. The implication of these results for the excitation of OH and the pumping of OH masers is briefly discussed.

Cohen, R. J.; Masheder, M. R. W.; Walker, R. N. F.

1991-06-01

131

In vitro characterization of corneal wound healing using multiphoton autofluorescence and second harmonic generation (SHG) microscopy  

NASA Astrophysics Data System (ADS)

The purpose of this investigation is to characterize corneal wound healing under in vitro conditions. Multiphoton autofluorescence and second harmonic generation (SHG) microscopy will be used to visualize cells and collagen fibers associated with corneal wound healing. Using the near-infrared excitation source from a titanium-sapphire laser pumped by a diode-pumped, solid state (DPSS) laser system, we can induce and simultaneously acquire multiphoton autofluorescence and SHG signals from the cornea specimens. A home-modified commercial microscope system with specified optical components is used for optimal signal detection. To acquire both high resolution and tissue-level information of the specimen, a sample positioning stage is used in conjunction with the beam scanning system. Finally, the organ level image can be assembled from individual area scans. The in vitro samples we used are cornea buttons acquired from porcine eyes. Localized wounds will be induced by #11 blade and imaged using multiphoton microscopy. Based on these results, we envision the in vitro imaging chamber to be able to follow the wound healing process without damaging histological procedures. We envision this approach will enable us to further understand wound healing process associated with corneal scar and can lead to in vivo methodology for diagnosing cornea damage.

Sun, Yen; Lo, Wen; Chen, Wei-Liang; Teng, Shu-Wen; Tan, Hsin-Yuan; Dong, Chen-Yuan

2006-03-01

132

New infrared photon absorption processes. Final technical progress report, August 1, 1988--February 1, 1993  

SciTech Connect

The fast ionization of atoms by very short laser pulses, and its possible suppression at extreme pulse intensities, is an active new field of investigation at present. Described is an investigation of whether past techniques for infrared laser multiphoton ionization of excited hydrogen atoms and of one-dimensional microwave ionization of highly excited hydrogen atoms can be combined and extended to address the new issues. Although technically difficult and requiring further improvement of apparatus, intense-field infrared laser experiments on excited hydrogen atoms are possible and can directly test theoretical and numerical results.

Bayfield, J.E.

1993-05-01

133

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.; K鰊ig, K.

2012-02-01

134

Energy partitioning in the collision-free multiphoton dissociation of molecules: Energy of ? CF2 from CF2HCl, CF2Br2, and CF2Cl2  

Microsoft Academic Search

We have developed a simple laser-excited fluorescence method to determine the translational energy of the nascent products of infrared multiphoton dissociations, and have applied this method to the measurement of the average translational energy ET of the ? 1A1 CF2 radicals formed from the collision-free dissociation of CF2HCl, CF2Br2, and CF2Cl2 by CO2 TEA laser pulses. The initially formed CF2

John C. Stephenson; David S. King

1978-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

136

Multi-photon ionization of lithium  

Microsoft Academic Search

A systematic study of multi-photon ionization (MPI) of atomic lithium in ultra-short and intense near-infrared laser pulses has been conducted both experimentally and theoretically. The cross section was measured for intensities spanning across the transition from MPI to over-the-barrier ionization (OBI). It turns out that this transition manifests itself in a substantial change in the photo-electron angular distributions. In a

Michael Schuricke; Ganjun Zhu; Jochen Steinmann; Igor Ivanov; Anatoli Kheifets; Alexei Grum-Grzhimailo; Klaus Bartschat; Alexander Dorn; Joachim Ullrich

2009-01-01

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爊m 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燾m?1, showing partial ground-state recovery, and in the excited electronic state at 1625燾m?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

An atomic jet in a heat pipe for multiphoton spectroscopy.  

PubMed

A conventional heat pipe is modified to operate as a novel atomic jet setup with unprecedented advantages for multiphoton spectroscopy of alkaline-earth atoms especially to study the effect of external electric field, controlled excitation of forbidden transitions and for the study of collisional broadening and shift of excited states, and time evolution of Rydberg atoms. PMID:18052459

Philip, G

2007-11-01

139

Multiphoton Microwave Ionization of Rydberg Atoms  

NASA Astrophysics Data System (ADS)

This thesis describes a series of multiphoton microwave experiments on Rydberg atoms when the microwave frequency is much greater than the classical Kepler frequency of the excited atoms. A new kHz pulse repetition frequency dye laser system was constructed for Rydberg lithium excitation with a linewidth as narrow as 3 GHz. This new laser system is used for first experiments of multiphoton microwave ionization of Rydberg lithium approaching the photoionization limit using 17 and 36 GHz microwave pulses. A multi-channel quantum defect model is presented that well describes the experimental results, indicating that these results are due to the coherent coupling of many atomic levels both above and below the classical ionization limit. Finally, preliminary results of measuring the final-state distributions of high lying Rydberg states after 17 GHz microwave pulses are presented.

Gurian, Joshua Houston

140

Multiphoton excitation and ionization by elliptically polarized, intense short laser pulses: Recognizing multielectron dynamics and doorway states in C60 vs Xe  

NASA Astrophysics Data System (ADS)

Ionization and fragmentation of C60 fullerenes are studied by time-of-flight mass spectrometry, in elliptically polarized femtosecond laser fields at 797 nm of intensities I0=(0.5-4.3)1014Wcm-2 . Xe atoms serve as a test case. We derive a qualitative theory describing such polarization studies. It turns out that polarization dependence can very sensitively distinguish single active electron (SAE) and multiple active electrons dynamics. In the case of Xe a clear signature of SAE dynamics is observed, with very pronounced changes in the ion yield as a function of ellipticity, indicative of N=5-8 and 18-22 photon processes for Xe+ and Xe2+ , respectively. In contrast, only a moderate polarization dependence is observed in the C60 case, although at least 5 h? photons at 797 nm are needed to generate C60+ and additional 11 for C602+ . At lower intensities, a moderate reduction in the ion yield for circular polarization establishes a two-photon SAE absorption process, connected with the key role of the lowest unoccupied molecular orbital (LUMO)+1(t1g) as 揹oorway state. The absence of any polarization effect at 399 nm corroborates this finding. At high intensities enhanced fragmentation is observed, which is tentatively attributed to returning loops of electron trajectories by the combined action of the C60+ field and the circularly polarized laser field梚n contrast to conventional wisdom that linear polarization should lead to an enhanced recolliding electron yield. No sign of a pronounced multiphoton polarization signature with five and more photons is seen for C60 which would be predicted by the SAE picture梐lthough the slopes of the ion yield as a function of intensity are given by the corresponding power laws ?I0N . This is taken as clear evidence of multielectron dynamics after reaching the doorway state.

Shchatsinin, I.; Ritze, H.-H.; Schulz, C. P.; Hertel, I. V.

2009-05-01

141

Multiphoton Processes in Homopolar Diatomic Molecules  

Microsoft Academic Search

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

F. V. Bunkin; I. I. Tugov

1973-01-01

142

Proton formation in 2+1 resonance enhanced multiphoton excitation of HCl and HBr via (Omega=0) Rydberg and ion-pair states  

Microsoft Academic Search

Molecular beam cooled HCl was state selected by two-photon excitation of the V 1?(0+) [v=9,11-13,15], E 1?(0+) [v=0], and g 3?-(0+) [v=0] states through either the Q(0) or Q(1) lines of the respective 1,3?(0+)<--<--X 1?(0+) transition. Similarly, HBr was excited to the V 1?(0+) [v=m+3, m+5-m+8], E 1?(0+) [v=0], and H 1?(0+) [v=0] states through the Q(0) or Q(1) lines.

Constantin Romanescu; Hans-Peter Loock

2007-01-01

143

Design of an infrared laser pulse to control the multiphoton dissociation of the Fe-CO bond in CO-heme compounds  

NASA Astrophysics Data System (ADS)

Optimal control theory is used to design a laser pulse for the multiphoton dissociation of the Fe-CO bond in the CO-heme compounds. The study uses a hexacoordinated iron-porphyrin-imidazole-CO complex in its ground electronic state as a model for CO liganded to the heme group. The potential energy and dipole moment surfaces for the interaction of the CO ligand with the heme group are calculated using density functional theory. Optimal control theory, combined with a time-dependent quantum dynamical treatment of the laser-molecule interaction, is then used to design a laser pulse capable of efficiently dissociating the CO-heme complex model. The genetic algorithm method is used within the mathematical framework of optimal control theory to perform the optimization process. This method provides good control over the parameters of the laser pulse, allowing optimized pulses with simple time and frequency structures to be designed. The dependence of photodissociation yield on the choice of initial vibrational state and of initial laser field parameters is also investigated. The current work uses a reduced dimensionality model in which only the Fe-C and C-O stretching coordinates are explicitly taken into account in the time-dependent quantum dynamical calculations. The limitations arising from this are discussed in Sec. IV.

Sharma, Sitansh; Singh, Harjinder; Harvey, Jeremy N.; Balint-Kurti, Gabriel G.

2010-11-01

144

Multiphoton excitation and ionization by elliptically polarized, intense short laser pulses: Recognizing multielectron dynamics and doorway states in C{sub 60} vs Xe  

SciTech Connect

Ionization and fragmentation of C{sub 60} fullerenes are studied by time-of-flight mass spectrometry, in elliptically polarized femtosecond laser fields at 797 nm of intensities I{sub 0}=(0.5-4.3)x10{sup 14} W cm{sup -2}. Xe atoms serve as a test case. We derive a qualitative theory describing such polarization studies. It turns out that polarization dependence can very sensitively distinguish single active electron (SAE) and multiple active electrons dynamics. In the case of Xe a clear signature of SAE dynamics is observed, with very pronounced changes in the ion yield as a function of ellipticity, indicative of N=5-8 and 18-22 photon processes for Xe{sup +} and Xe{sup 2+}, respectively. In contrast, only a moderate polarization dependence is observed in the C{sub 60} case, although at least 5 h{nu} photons at 797 nm are needed to generate C{sub 60}{sup +} and additional 11 for C{sub 60}{sup 2+}. At lower intensities, a moderate reduction in the ion yield for circular polarization establishes a two-photon SAE absorption process, connected with the key role of the lowest unoccupied molecular orbital (LUMO)+1(t{sub 1g}) as 'doorway state'. The absence of any polarization effect at 399 nm corroborates this finding. At high intensities enhanced fragmentation is observed, which is tentatively attributed to returning loops of electron trajectories by the combined action of the C{sub 60}{sup +} field and the circularly polarized laser field - in contrast to conventional wisdom that linear polarization should lead to an enhanced recolliding electron yield. No sign of a pronounced multiphoton polarization signature with five and more photons is seen for C{sub 60} which would be predicted by the SAE picture - although the slopes of the ion yield as a function of intensity are given by the corresponding power laws {proportional_to}I{sub 0}{sup N}. This is taken as clear evidence of multielectron dynamics after reaching the doorway state.

Shchatsinin, I.; Ritze, H.-H.; Schulz, C. P.; Hertel, I. V. [Max Born Institute, Max-Born-Str. 2a, D-12489 Berlin-Adlershof (Germany)

2009-05-15

145

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.  

PubMed

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 degrees C. This novel method for the dissociation of large biomolecular ions is termed "heat-assisted NS-CID" (HANS-CID) or "heat-assisted IRMPD" (HA-IRMPD). Multiple charged nonreduced protein ions (8.6 Da ubiquitin, 14 kDa lysozyme, and 67 kDa bovine serum albumin) were directly dissociated by HANS-CID and HA-IRMPD to effectively yield fragment ions that could be assigned. The fragment ions of ubiquitin by HANS-CID can be analyzed by tandem mass spectrometry (MS/MS) using sustained off-resonance irradiation CID (SORI-CID) and IRMPD. In addition, a native large protein, immunoglobulin G (IgG, 150 kDa), was efficiently dissociated by HA-IRMPD. The product ions that were obtained reflected the domain structure of IgG. However, these product ions of IgG and lysozyme were not dissociated by MS/MS using the same heating energetic methods such as IRMPD and SORI-CID. PMID:16298327

Yamada, Naoyuki; Suzuki, Ei-Ichiro; Hirayama, Kazuo

2005-11-02

146

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?礸/g, dw) and 4-hydroxyglucobrassicin (89??12?礸/g, dw). All other compounds were present at very low content ranging from 0.5 to 1.5?礸/g dw. PMID:22972784

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

2012-09-01

147

Proton formation in 2+1 resonance enhanced multiphoton excitation of HCl and HBr via (?=0) Rydberg and ion-pair states  

NASA Astrophysics Data System (ADS)

Molecular beam cooled HCl was state selected by two-photon excitation of the V 1?(0+) [v=9,11-13,15], E 1?(0+) [v=0], and g 3?-(0+) [v=0] states through either the Q(0) or Q(1) lines of the respective 1,3?(0+)<--<--X 1?(0+) transition. Similarly, HBr was excited to the V 1?(0+) [v=m+3, m+5-m+8], E 1?(0+) [v=0], and H 1?(0+) [v=0] states through the Q(0) or Q(1) lines. Following absorption of a third photon, protons were formed by three different mechanisms and detected using velocity map imaging. (1) H*(n=2) was formed in coincidence with 2Pi halogen atoms and subsequently ionized. For HCl, photodissociation into H*(n=2)+Cl(2P1/2) was dominant over the formation of Cl(2P3/2) and was attributed to parallel excitation of the repulsive [(2) 2?..4l?] superexcited (?=0) states. For HBr, the Br(2P3/2)/Br(2P1/2) ratio decreases with increasing excitation energy. This indicates that both the [(3) 2?1/2..5l?] and the [B 2?..5l?] superexcited (?=0) states contribute to the formation of H*(n=2). (2) For selected intermediate states HCl was found to dissociate into the H++Cl- ion pair with over 20% relative yield. A mechanism is proposed by which a bound [A 2?..nl?] 1?(0+) superexcited state acts as a gateway state to dissociation into the ion pair. (3) For all intermediate states, protons were formed by dissociation of HX+[v+] following a parallel, ??=0, excitation. The quantum yield for the dissociation process was obtained using previously reported photoionization efficiency data and was found to peak at v+=6-7 for HCl and v+=12 for HBr. This is consistent with excitation of the repulsive A2?1/2 and (2) 2? states of HCl+, and the (3) 2? state of HBr+. Rotational alignment of the ?=0+ intermediate states is evident from the angular distribution of the excited H*(n=2) photofragments. This effect has been observed previously and was used here to verify the reliability of the measured spatial anisotropy parameters.

Romanescu, Constantin; Loock, Hans-Peter

2007-09-01

148

White light excitation of the near infrared Er3+ emission in exchanged zeolite sensitised by oxygen vacancies.  

PubMed

A new material based on Er(3+)-exchanged zeolite L crystals, in which oxygen vacancies have been generated, is proposed as an efficient emitter in the near infrared third telecommunication window. The rare earth ions photoluminescence is efficiently generated by energy transfer from the excited oxygen vacancies, which act as wide range light harvesters. The proposed material can be excited in the whole Near UV-VIS-NIR spectral range from 355 to 700 nm, thus representing the first step toward versatile, zeolite based NIR sources that can be excited with white light. PMID:21298167

Mech, Agnieszka; Monguzzi, Angelo; Cucinotta, Fabio; Meinardi, Francesco; Mezyk, Jakub; De Cola, Luisa; Tubino, Riccardo

2011-02-07

149

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

150

A comparison of enhancement factors for surface-enhanced Raman scattering using visible and near-infrared excitations  

NASA Astrophysics Data System (ADS)

We investigated enhancement factors for surface-enhanced Raman scattering from p-aminobenzoic acid (PABA) on different silver and gold substrates using visible (632.8 nm) and near-infrared (NIR) (1064 nm) excitations. The results indicated that the use of NIR excitation provided larger enhancements (about 10 100 times) than those obtained using the visible excitation. The enhancement factors for the PABA on the silver coated alumina, silver island, gold-coated alumina, and gold island are 2.7106, 4.3105, 3.0104, and 6.0103, respectively, with the NIR excitation, and are 4.6104, 4.7103, 1.2103, and 6.0102, respectively, with the visible excitation.

Ibrahim, Amin; Oldham, Philip B.; Stokes, David L.; Vo-Dinh, Tuan; Loo, Boon H.

2005-02-01

151

Multiphoton excitation of autoionizing states of Mg: Line-shape studies of the 3p/sup 2/ /sup 1/S state  

SciTech Connect

We have observed ionization of Mg by both direct and stepwise two-photon excitation of the 3p/sup 2/ /sup 1/S state. The line shape of the single-color direct process is strongly modified by the resonance denominator associated with the intermediate virtual state. The measured energy and width of this resonance as determined by the stepwise two-color technique agree well with previous determinations.

Bonanno, R.E.; Clark, C.W.; Lucatorto, T.B.

1986-09-01

152

Gene inactivation by multiphoton-targeted photochemistry  

PubMed Central

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

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

2000-01-01

153

Free electron laser-Fourier transform ion cyclotron resonance mass spectrometry facility for obtaining infrared multiphoton dissociation spectra of gaseous ions  

SciTech Connect

A Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer has been installed at a free electron laser (FEL) facility to obtain infrared absorption spectra of gas phase ions by infrared multiple photon dissociation (IRMPD). The FEL provides continuously tunable infrared radiation over a broad range of the infrared spectrum, and the FT-ICR mass spectrometer, utilizing a 4.7 Tesla superconducting magnet, permits facile formation, isolation, trapping, and high-mass resolution detection of a wide range of ion classes. A description of the instrumentation and experimental parameters for these experiments is presented along with preliminary IRMPD spectra of the singly-charged chromium-bound dimer of diethyl ether (Cr(C{sub 4}H{sub 10}O){sub 2}{sup +}) and the fluorene molecular ion (C{sub 13}H{sub 10}{sup +}). Also presented is a brief comparison of the fluorene cation spectrum obtained by the FT-ICR-FEL with an earlier spectrum recorded using a quadrupole ion trap (QIT)

Valle, Jose J.; Eyler, John R.; Oomens, Jos; Moore, David T.; Meer, A.F.G. van der; Helden, Gert von; Meijer, Gerard; Hendrickson, Christopher L.; Marshall, Alan G.; Blakney, Gregory T. [Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200 (United States); FOM-Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, NL-3439 MN Nieuwegein (Netherlands); FOM-Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, NL-3439 MN Nieuwegein (Netherlands); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310-4005 (United States); Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306 (United States); National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310-4005 (United States)

2005-02-01

154

Coherent Control in Multiphoton Fluorescence Imaging  

PubMed Central

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

De, Arijit Kumar; Goswami, Debabrata

2013-01-01

155

Clinical multiphoton endoscopy with FLIM capability  

NASA Astrophysics Data System (ADS)

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

Weinigel, Martin; Breunig, Hans Georg; Fischer, Peter; Kellner-H鰂er, Marcel; B點kle, Rainer; K鰊ig, Karsten

2013-02-01

156

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.

K鰊ig, Karsten

2012-02-01

157

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

158

Characterizing lamina propria of human gastric mucosa by multiphoton microscopy  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

159

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

SciTech Connect

The infrared multiple-photon dissociation (IRMPD) spectra of protonated acenaphthene ([ACN+H]{sup +}) and 9,10-dihydrophenanthrene ([DHP+H]{sup +}) have been recorded using an infrared free electron laser after the compounds were protonated by electrospray ionization and trapped in a Fourier transform ion cyclotron mass spectrometer. In both compounds, the loss of two mass units is predominant. Density functional calculations (B3LYP/6-311++G(d,p)) of the infrared spectra of all possible protonated isomers of each species showed that the observed IRMPD spectra are best fit to the isomer with the largest proton affinity and lowest relative electronic energy. Potential energy surfaces of the most stable isomers of [ACN+H]{sup +} and [DHP+H]{sup +} have been calculated for H and H{sub 2} loss. The lowest energy barriers are for loss of H{sub 2}, with predicted energies 4.28 and 4.15 eV, respectively. After H{sub 2} ejection, the adjacent aliphatic hydrogens migrate to the bare ejection site and stabilize the remaining fragment. Single H loss may occur from [ACN+H]{sup +} but the energy required is higher. No single H loss is predicted from [DHP+H]{sup +}, only H migration around the carbon skeleton. The vibrational bands in the parent closed-shell protonated polycyclic aromatic hydrocarbons are compared to bands observed from the interstellar medium.

Szczepanski, Jan; Vala, Martin T. [Department of Chemistry and Center for Chemical Physics, P.O. Box 117200, University of Florida, Gainesville, FL 32611-7200 (United States); Oomens, Jos; Steill, Jeffrey D. [FOM Institute for Plasma Physics 'Rijnhuizen', Edisonbaan 14, NL-3439MN Nieuwegein (Netherlands)

2011-01-20

160

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

161

Red-emitting upconverting nanoparticles for photodynamic therapy in cancer cells under near-infrared excitation.  

PubMed

Upconverting nanoparticles (UCNPs) have attracted considerable attention as potential photosensitizer carriers for photodynamic therapy (PDT) in deep tissues. In this work, a new and efficient NIR photosensitizing nanoplatform for PDT based on red-emitting UCNPs is designed. The red emission band matches well with the efficient absorption bands of the widely used commercially available photosensitizers (Ps), benefiting the fluorescence resonance energy transfer (FRET) from UCNPs to the attached photosensitizers and thus efficiently activating them to generate cytotoxic singlet oxygen. Three commonly used photosensitizers, including chlorine e6 (Ce6), zinc phthalocyanine (ZnPc) and methylene blue (MB), are loaded onto the alpha-cyclodextrin-modified UCNPs to form Ps@UCNPs complexes that efficiently produce singlet oxygen to kill cancer cells under 980 nm near-infrared excitation. Moreover, two different kinds of drugs are co-loaded onto these nanoparticles: chemotherapy drug doxorubicin and PDT agent Ce6. The combinational therapy based on doxorubicin (DOX)-induced chemotherapy and Ce6-triggered PDT exhibits higher therapeutic efficacy relative to the individual means for cancer therapy in vitro. PMID:23239556

Tian, Gan; Ren, Wenlu; Yan, Liang; Jian, Shan; Gu, Zhanjun; Zhou, Liangjun; Jin, Shan; Yin, Wenyan; Li, Shoujian; Zhao, Yuliang

2012-12-13

162

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-H鰂er, Marcel; B點kle, Rainer; K鰊ig, Karsten

2010-02-01

163

Fourier transform infrared spectroscopy of electronic excitations to probe magnetic order and phase transitions in solid oxygen  

Microsoft Academic Search

Systematic Fourier transform infrared (FTIR) spectroscopic investigations of interaction-induced electronic transitions 3Sigma-g- 1Deltag (v=0,...,3) of solid and liquid oxygen were carried out in the temperature range 10-90 K at ambient pressure. We interpret these absorption bands as phonon sidebands to an electronic (or an electronic-vibrational) excitations plus (in alpha-O2) exciton (-vibron)-magnon bound states. A consistent description of electronic spectra in

S. A. Medvedev; A. P. Brodyanski; H. J. Jodl

2001-01-01

164

Multiphoton Assisted Recombination  

SciTech Connect

We have observed multiphoton assisted recombination in the presence of a 38.8 GHz microwave field. Stimulated emission of up to ten microwave photons results in energy transfer from continuum electrons, enabling recombination. The maximum electron energy loss is far greater than the 2U{sub p} predicted by the standard 'simpleman's' model. The data are well reproduced by both an approximate analytic expression and numerical simulations in which the combined Coulomb and radiation fields are taken into account.

Shuman, E. S.; Jones, R. R.; Gallagher, T. F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904-4714 (United States)

2008-12-31

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

2012-12-06

166

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

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

2013-03-03

168

Photonic near-field imaging in multiphoton photoemission electron microscopy  

NASA Astrophysics Data System (ADS)

We report the observation of optical near fields in a photonic waveguide of conductive indium tin oxide (ITO) using multiphoton photoemission electron microscopy (PEEM). Nonlinear two-photon photoelectron emission is enhanced at field maxima created by interference between incident 410-nm and coherently excited guided photonic waves, providing strong phase contrast. Guided modes are observed under both transverse magnetic field (TM) and transverse electric field (TE) polarized illuminations and are consistent with classical electromagnetic theory. Implications on the role of multiphoton PEEM in optical near-field imaging are discussed.

Fitzgerald, J. P. S.; Word, R. C.; Saliba, S. D.; K鰊enkamp, R.

2013-05-01

169

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

170

Efficient Nonlinear Light Emission of Single Gold Optical Antennas Driven by Few-Cycle Near-Infrared Pulses  

Microsoft Academic Search

Individual nanometer-sized plasmonic antennas are excited resonantly with few-cycle laser pulses in the near infrared. Intense third-harmonic emission of visible light prevails for fundamental photon energies below 1.1 eV. Interband luminescence and second harmonic generation occur solely at higher driving frequencies. We attribute these findings to multiphoton resonances with the d-band transitions of gold. The strong third-order signal allows direct

T. Hanke; G. Krauss; D. Tr鋟tlein; B. Wild; R. Bratschitsch; A. Leitenstorfer

2009-01-01

171

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

172

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.

K鰊ig, Karsten

2011-02-01

173

CO2 non-local thermodynamic equilibrium radiative excitation and infrared dayglow at 4.3 micron: Application to Spectral Infrared Rocket Experiment data  

NASA Astrophysics Data System (ADS)

Infrared radiative excitation in non-local thermodynamic equilibrium (non-LTE) regions of the Earth's atmosphere for the V(sub 3) mode vibrationally excited states of CO2 under sunlit conditions and the resulting 4.3-microns limb radiance are calculated using a line-by-line (LBL) radiative transfer model. Excited-state popluation densities and the corresponding vibrational temperature profiles are calculated for the important emitting states using a model which includes radiative absorption and emission as well as various collisional processes. The quenching of O(D(1)/by N2 has a greater impact on these population densities than has been previously reported in the literature. Integrated radiance in a limb view for the 4.3-microns bands is calculated from the model and compared with sunlit earthlimb measurements obtained by the Spectral Infrared Rocket Experiment (SPIRE). Solar pumping is the dominant excitation process for the 4.3-micron emitting states in the daytime. The major contribution to the total limb radiance for tangent heights of 55-95 km is made by the flourescent states at approximately 3600/cm which absorb sunlight at 2.7 microns and then emit preferentially at 4.3 microns. The predicted radiance is in good agreement with the SPIRE measurements for all tangent heights in the 50- to 130-km range. This is the first detailed comparison of results of a full line-by-line non-LTE radiative transfer calculation with 4.3-microns earthlimb radiance data.

Nebel, Henry; Wintersteiner, Peter P.; Picard, R. H.; Winick, Jeremy R.; Sharma, Ramesh D.

1994-05-01

174

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

175

Probing collective excitations in helium nanodroplets: Observation of phonon wings in the infrared spectrum of methane  

Microsoft Academic Search

The authors have recorded the nu3 infrared spectrum of methane in helium nanodroplets using our cw infrared optical parametric oscillator. In a previous paper, Nauta and Miller [Chem. Phys. Lett. 350, 225 (2001)] reported the observation of the monomer rovibrational transitions of methane in helium nanodroplets. Here, they report the observation of additional absorption bands in the frequency range between

S. Rudolph; G. Wollny; K. von Haeften; M. Havenith

2007-01-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

177

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

178

Detecting excited-state vibrational dynamics by broadband infrared or Raman probes; A unified picture based on loop diagrams  

NASA Astrophysics Data System (ADS)

Vibrational motions in electronically excited states can be probed either by time and frequency resolved infrared or by off resonant stimulated Raman techniques. Using loop diagrams, which represent forward and backward propagation of the wavefunction we derive similar multipoint correlation function expressions for both signals which are suitable for quantum microscopic simulations. The effective temporal (?t) and spectral (??) resolution of the techniques is not solely controlled by experimental knobs since it also depends on the system dynamics being probed. The Fourier uncertainty ???t 1 is never violated.

Dorfman, Konstantin E.; Fingerhut, Benjamin; Mukamel, Shaul

2013-03-01

179

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

180

Acousto-optic multiphoton laser scanning microscopy and multiphoton photon counting spectroscopy: Applications and implications for optical neurobiology  

NASA Astrophysics Data System (ADS)

Multiphoton excitation of molecular probes has become an important tool in experimental neurobiology owing to the intrinsic optical sectioning and low light scattering it affords. Using molecular functional indicators, multiphoton excitation allows physiological signals within single neurons to be observed from within living brain tissue. Ideally, it would be possible to record from multiple sites located throughout the elaborately branching dendritic arbors, in order to study the correlations of structure and function both within and across experiments. However, existing multiphoton microscope systems based on scanning mirrors do not allow optical recordings to be obtained from more than a handful of sites simultaneously at the high rates required to capture the fast physiological signals of interest (>100Hz for Ca2+ signals, >1kHz for membrane potential transients). In order to overcome this limitation, two-dimensional acousto-optic deflection was employed, to allow an ultrafast laser beam suited for multiphoton excitation to be rapidly repositioned with low latency (15mus). This supports a random-access scanning mode in which the beam can repeatedly visit a succession of user-selected sites of interest within the microscope's field-of-view at high rates, with minimal sacrifice of pixel dwell time. This technique of acousto-optic multiphoton laser scanning microscope (AO-MPLSM) was demonstrated to allow the spatial profile of signals arising in response to physiological stimulation to be rapidly mapped. Means to compensate or avoid problems of dispersion which have hampered AO-MPLSM in the past are presented, with the latter being implemented. Separately, the combination of photon counting detection with multiphoton excitation, termed generally multiphoton photon counting spectroscopy (MP-PCS), was also considered, with particular emphasis on the technique of fluorescence correlation spectroscopy (FCS). MP-PCS was shown to allow information about molecular numbers and mobility, as well as the focal volume itself, to be obtained. This capability may in the future be employed to study the number and transport of native neuronal signaling molecules. MP-PCS was also found to be a promising off-line tool which can allow the performance of AO-MPLSM to be optimized, with respect to both the instrument and the indicators employed.

Iyer, Vijay

181

The excitation of near-infrared H2 emission in NGC 253  

NASA Astrophysics Data System (ADS)

Context. Because of its large angular size and proximity to the Milky Way, NGC 253, an archetypal starburst galaxy, provides an excellent laboratory to study the intricacies of this intense episode of star formation. Aims: We aim to characterize the excitation mechanisms driving the emission in NGC 253. Specifically we aim to distinguish between shock excitation and ultraviolet (UV) excitation as the dominant driving mechanism, using Br?, H2 and [FeII] as diagnostic emission line tracers. Methods: Using SINFONI observations, we create linemaps of Br?, [FeII]1.64, and all detected H2 transitions. By using symmetry arguments of the gas and stellar gas velocity field, we find a kinematic center in agreement with previous determinations. The ratio of the 2-1 S(1) to 1-0 S(1) H2 transitions can be used as a diagnostic to discriminate between shock and fluorescent excitation. Results: Using the 1-0 S(1)/2-1 S(1) line ratio as well as several other H2 line ratios and the morphological comparison between H2 and Br? and [FeII], we find that excitation from UV photons is the dominant excitation mechanisms throughout NGC 253. We employ a diagnostic energy level diagram to quantitatively differentiate between mechanisms. We compare the observed energy level diagrams to photon-dominated region (PDR) and shock models and find that in most regions and over the galaxy as a whole, fluorescent excitation is the dominant mechanism exciting the H2 gas. We also place an upper limit of the percentage of shock excited H2 at 29%. Conclusions: We find that UV radiation is the dominant excitation mechanism for the H2 emission. The H2 emission does not correlate well with Br? but closely traces the polycyclic aromatic hydrocarbon emission, showing that not only is H2 fluorescently excited, but it is predominately excited by slightly lower mass stars than O stars which excite Br?, such as B stars. Reduced datacubes and extracted images for each line are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/550/A12

Rosenberg, M. J. F.; van der Werf, P. P.; Israel, F. P.

2013-02-01

182

Transverse correlations in multiphoton entanglement  

SciTech Connect

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

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

2007-10-15

183

Transverse correlations in multiphoton entanglement  

Microsoft Academic Search

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

Jianming Wen; Morton H. Rubin; Yanhua Shih

2007-01-01

184

Transverse correlations in multiphoton entanglement  

NASA Astrophysics Data System (ADS)

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

Wen, Jianming; Rubin, Morton H.; Shih, Yanhua

2007-10-01

185

Transverse correlations in multiphoton entanglement  

Microsoft Academic Search

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

Wen Jianming; Morton H. Rubin; Shih Yanhua

2007-01-01

186

Study of crystal-field excitations and infrared active phonons in the multiferroic hexagonal燚yMnO3.  

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燢. Between TN=68燢 and T=10燢, 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燢, 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燢, 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

2013-10-31

187

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 20016045 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

188

Developing compact multiphoton systems using femtosecond fiber lasers  

NASA Astrophysics Data System (ADS)

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 20016045 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.

2009-05-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

190

Multiphoton processes in complex atoms and ions  

NASA Astrophysics Data System (ADS)

After setting the work within its historical context an outline of recent developments in the field of multiphoton processes is given. The first chapter concludes with a description of some of the alternative theoretical approaches. In the second chapter the R- matrix-Floquet theory is presented with two new components being introduced. The first of these involves solving linear equations instead of diagonalising a large matrix, while the second includes 'dressed' channel momenta which, although unphysical, enable fewer terms to be retained in the Floquet expansion. Chapter three takes up the discussion of the different linear equation approaches and compares timings for these as well as for the original diagonalisation. Some results are also presented for the parallelisation of the two methods. In chapter four multiphoton ionisation of helium is considered at frequencies where double resonances with a bound state and autoionising states are important. It is found that, in the three-state approximation used, an adiabatic transfer of population from the 1s2/ 1Se ground state to the 1s2p/ 1Po bound state via the (2s3p-2p3s)1Po autoionising state is possible at an intensity of 51012Wcm-2. Results for the two-photon detachment of Li/sp- at an intensity of 1010Wcm-2 are presented in chapter five. Agreement with other theoretical work is obtained at low frequencies where absorption of two photons is necessary for detachment to occur. At higher frequencies there is a great deal of resonance structure due to the possibility of exciting doubly-excited states. Other structure arises from the excitation of the core after detachment has taken place and from light induced continuum structure where the two photon rate is affected by structure in the three-photon rate. Finally, the work is summarised and future directions are indicated in chapter six.

Glass, David Herbert

1997-06-01

191

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

192

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

193

Optimization of the design of a multiple-photon excitation laser scanning fluorescence imaging system  

Microsoft Academic Search

Multi-photon (two or more photon) excitation imaging offers three significant advantages compared to laser-scanning confocal fluorescence microscopy for 3-D and 4-D fluorescence microscopy: considerable reduction in total sample excitation, increased depth penetration, and increased detection sensitivity. All-solid-state ultra-fast lasers offer tremendous potential for affordable, reliable, 'turn-key' multi-photon excitation sources. We have been developing a multi-photon system that utilizes an all-solid-

David L. Wokosin; John G. White

1997-01-01

194

Multiphoton nanosurgery in cells and tissues  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

195

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

PubMed

Molecular beam investigations in combination with IR/UV spectroscopy offer the possibility to obtain structural information on isolated molecules and clusters. One of the demanding tasks is the discrimination of different isomers, e.g., by the use of isomer specific UV excitations. If this discrimination fails due to overlaying UV spectra of different isomers, IR/IR methods offer another possibility. Here, we present a new IR/UV/IR/UV quadruple resonance technique to distinguish between different isomers especially in the electronically excited state. Due to the IR spectra, structural changes and photochemical pathways in excited states can be assigned and identified. The method is applied to the dihydrated cluster of 3-hydroxyflavone which has been investigated as photochemically relevant system and proton wire model in the S(1) state. By applying the new IR/UV/IR/UV technique, we are able to show experimentally that both in the electronic ground (S(0)) and the electronically excited state (S(1)) two isomers have to be assigned. PMID:22443757

Weiler, M; Bartl, K; Gerhards, M

2012-03-21

196

Luminescence and infrared absorption from laser excitation of trapped electrons in aqueous glasses  

Microsoft Academic Search

When samples of trapped electrons in 9.5M LiCl and 3.1M MgCl2 aqueous glasses at 77 K were bleached by single pulses of 694 nm light from a Q-switched ruby laser, infrared absorption was produced, and luminescence observed in the near ultraviolet and visible. The luminescence had a spectrum centered at 400420 nm and its intensity was measured over eight decades

Hugh A. Gillis; David C. Walker

1976-01-01

197

Infrared laser emission from a helium-xenon mixture using fission fragment excitation  

Microsoft Academic Search

An experiment which proves the feasibility of directly converting nuclear reaction energy into laser light is reported. A two-section, 1-meter-long laser device was placed next to the Los Alamos Godiva IV fast burst nuclear reactor. One section of the laser cavity was lined with a 0.05-mm-thick, 93% enriched uranium foil. An infrared laser pulse was generated from a fission fragment

J. L. Fuller

1975-01-01

198

Excitation of the inner pc of the Galactic Center: Results from near-infrared spectroscopy  

Microsoft Academic Search

We present near-infrared spectroscopy and line imaging of the central 0.5 pc of the Galaxy. The ``mini-cavity'' region south-west of SgrA* is a source of bright 2.217 mum emission now identified as due to [Fe III]. We infer that iron is released from grains in shocks triggered by fast wind blowing into the Galactic Center gas streamers. After cooling the

D. Lutz; R. Genzel; A. Krabbe; M. Blietz; S. Drapatz; P. P. van der Werf; F. Najarro; D. J. Hillier

1994-01-01

199

Near-infrared excitation of the Q band in free base and zinc tetratolyl-porphyrins.  

PubMed

The photophysics of 5,10,15,20-tetra-p-tolyl-21H,23H-porphyrin (TTP-H2) and 5,10,15,20-tetra-p-tolyl-porphyrinato zinc II (ZnTTP) have been investigated by means of pump-probe and transient anisotropy experiments. After excitation to the Q band, the molecules were probed by NIR pulses in the range between 950 and 1350 nm in order to study states of gerade symmetry in the vicinity of the Soret band. Examination of transient spectra and anisotropy delivered the first direct observation and the excitation energies of the two lowest so-called dark states. The experimental results were compared with predictions from theoretical calculations. PMID:18251524

Schalk, Oliver; Brands, Helge; Balaban, Teodor Silviu; Unterreiner, Andreas-Neil

2008-02-06

200

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

201

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

202

Resonance Raman spectroscopy of red blood cells using near-infrared laser excitation  

Microsoft Academic Search

Resonance Raman spectra of oxygenated and deoxygenated functional erythrocytes recorded using 785爊m laser excitation are\\u000a presented. The high-quality spectra show a mixture of enhanced A1g, A2g, B1g, B2g, Eu and vinyl modes. The high sensitivity of the Raman system enabled spectra from four oxygenation and deoxygenation cycles\\u000a to be recorded with only 18爉W of power at the sample over a

Bayden R. Wood; Peter Caspers; Gerwin J. Puppels; Shveta Pandiancherri; Don McNaughton

2007-01-01

203

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

NASA Astrophysics Data System (ADS)

We have mapped the warm molecular gas traced by the H2 S(0)-H2 S(5) pure rotational mid-infrared emission lines over a radial strip across the nucleus and disk of M51 (NGC 5194) using the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. The six H2 lines have markedly different emission distributions. We obtained the H2 temperature and surface density distributions by assuming a two-temperature model: a warm (T=100-300 K) phase traced by the low J [S(0)-S(2)] lines and a hot phase (T=400-1000 K) traced by the high J [S(2)-S(5)] lines. The lowest molecular gas temperatures are found within the spiral arms (T~155 K), while the highest temperatures are found in the inter-arm regions (T>700 K). The warm gas surface density reaches a maximum of 11 Msolar pc-2 in the northwest spiral arm, whereas the hot gas surface density peaks at 0.24 Msolar pc-2 at the nucleus. The spatial offset between the peaks in the different phases suggests that the warm phase is more efficiently heated by star formation activity and the hot phase is more efficiently heated by nuclear activity. The warm H2 is found in the dust lanes of M51 and is generally spatially coincident with the cold molecular gas traced by CO emission, consistent with excitation of the warm phase in dense photodissociation regions. The hot H2 is most prominent in the nuclear region. Here, the hot H2 coincides with [O IV] (25.89 ?m) and X-ray emission indicating that shocks and/or X-rays are responsible for exciting this phase.

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

2008-03-01

204

Singlet and triplet excitation management in a bichromophoric near-infrared-phosphorescent BODIPY-benzoporphyrin platinum complex.  

PubMed

Multichromophoric arrays provide one strategy for assembling molecules with intense absorptions across the visible spectrum but are generally focused on systems that efficiently produce and manipulate singlet excitations and therefore are burdened by the restrictions of (a) unidirectional energy transfer and (b) limited tunability of the lowest molecular excited state. In contrast, we present here a multichromophoric array based on four boron dipyrrins (BODIPY) bound to a platinum benzoporphyrin scaffold that exhibits intense panchromatic absorption and efficiently generates triplets. The spectral complementarity of the BODIPY and porphryin units allows the direct observation of fast bidirectional singlet and triplet energy transfer processes (k(ST)((1)BDP?(1)Por) = 7.8 10(11) s(-1), k(TT)((3)Por?(3)BDP) = 1.0 10(10) s(-1), k(TT)((3)BDP?(3)Por) = 1.6 10(10) s(-1)), leading to a long-lived equilibrated [(3)BDP][Por]?[BDP][(3)Por] state. This equilibrated state contains approximately isoenergetic porphyrin and BODIPY triplets and exhibits efficient near-infrared phosphorescence (?(em) = 772 nm, ? = 0.26). Taken together, these studies show that appropriately designed triplet-utilizing arrays may overcome fundamental limitations typically associated with core-shell chromophores by tunable redistribution of energy from the core back onto the antennae. PMID:21142032

Whited, Matthew T; Djurovich, Peter I; Roberts, Sean T; Durrell, Alec C; Schlenker, Cody W; Bradforth, Stephen E; Thompson, Mark E

2010-12-10

205

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

206

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

207

Advances in multiphoton microscopy technology  

NASA Astrophysics Data System (ADS)

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.

2013-02-01

208

Resonance Raman spectroscopy of red blood cells using near-infrared laser excitation.  

PubMed

Resonance Raman spectra of oxygenated and deoxygenated functional erythrocytes recorded using 785 nm laser excitation are presented. The high-quality spectra show a mixture of enhanced A(1g), A(2g), B(1g), B(2g), E(u) and vinyl modes. The high sensitivity of the Raman system enabled spectra from four oxygenation and deoxygenation cycles to be recorded with only 18 mW of power at the sample over a 60-minute period. This low power prevented photo-/thermal degradation and negated protein denaturation leading to heme aggregation. The large database consisting of 210 spectra from the four cycles was analyzed with principal components analysis (PCA). The PC1 loadings plot provided exquisite detail on bands associated with the oxygenated and deoxygenated states. The enhancement of a band at 567 cm(-1), observed in the spectra of oxygenated cells and the corresponding PC1 loadings plot, was assigned to the Fe-O(2) stretching mode, while a band appearing at 419 cm(-1) was assigned to the Fe-O-O bending mode based on previous studies. For deoxygenated cells, the enhancement of B(1g) modes at 785 nm excitation is consistent with vibronic coupling between band III and the Soret transition. In the case of oxygenated cells, the enhancement of iron-axial out-of-plane modes and non-totally symmetric modes is consistent with enhancement into the y,z-polarized transition a(iu)(pi)-->d(xz)+O(2)(pi(g)) centered at 785 nm. The enhancement of non-totally symmetric B(1g) modes in oxygenated cells suggests vibronic coupling between band IV and the Soret band. This study provides new insights into the vibrational dynamics, electronic structure and resonant enhancement of heme moieties within functional erythrocytes at near-IR excitation wavelengths. PMID:17151857

Wood, Bayden R; Caspers, Peter; Puppels, Gerwin J; Pandiancherri, Shveta; McNaughton, Don

2006-12-07

209

Multiphoton microscopy based cryo-imaging of inflated frozen human lung sections at -60癈 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癈 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癈 using a temperature controlled cold stage with a temperature resolution of 0.1癈. 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

210

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

211

Adiabatic passage on high-order multiphoton transitions  

SciTech Connect

Coherent interactions between light fields and simple quantum systems, such as {pi}-pulses and adiabatic passage through frequency chirps and stimulated Raman interactions, generally use one- or two-photon processes. This limits the use of such interactions to energy scales close to the photon energy of the control field. However, recent calculations have shown that a 3-level system, generic to ionized diatomic molecules, shows such a strong multiphoton coupling that {pi}-pulses are possible on at least 12-photon transitions. In this paper, we show that adiabatic transfer of population is also possible on such high-order multiphoton transitions. Full one-dimensional quantum mechanical two-electron calculations confirm this effect even in a system with many excited states and an ionization continuum.

Gibson, George N. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

2005-10-15

212

Differentiation of normal and cancerous lung tissues by multiphoton imaging  

NASA Astrophysics Data System (ADS)

We utilize multiphoton microscopy for the label-free diagnosis of noncancerous, lung adenocarcinoma (LAC), and lung squamous cell carcinoma (SCC) tissues from humans. Our results show that the combination of second-harmonic generation (SHG) and multiphoton excited autofluorescence (MAF) signals may be used to acquire morphological and quantitative information in discriminating cancerous from noncancerous lung tissues. Specifically, noncancerous 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) 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. Our study shows that nonlinear optical microscopy can assist in differentiating and diagnosing pulmonary cancer from noncancerous tissues.

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

2009-07-01

213

Adiabatic passage on high-order multiphoton transitions  

NASA Astrophysics Data System (ADS)

Coherent interactions between light fields and simple quantum systems, such as ? -pulses and adiabatic passage through frequency chirps and stimulated Raman interactions, generally use one- or two-photon processes. This limits the use of such interactions to energy scales close to the photon energy of the control field. However, recent calculations have shown that a 3-level system, generic to ionized diatomic molecules, shows such a strong multiphoton coupling that ? -pulses are possible on at least 12-photon transitions. In this paper, we show that adiabatic transfer of population is also possible on such high-order multiphoton transitions. Full one-dimensional quantum mechanical two-electron calculations confirm this effect even in a system with many excited states and an ionization continuum.

Gibson, George N.

2005-10-01

214

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

215

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 祄 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 祄 region, indicating a large elongation of the phenolic O-H bond (over 0.1 ) 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.

216

Three and four center elimination of HCl in the multiphoton dissociation of halogenated hydrocarbons  

Microsoft Academic Search

Three and four center unimolecular elimination reactions of HCl have been investigated for CHFCl, CHFCL, CHCCl, CHCFCl and in a molecular beam experiment using infrared multiphoton absorption to energize the molecule. The translational energy distributions obtained in this work show that the average translational energy released to the fragments is around 8-12 kcal\\/mole, except for the three center elimination reaction

Aa. S. Sudb; P. A. Schulz; Y. R. Shen; Y. T. Lee

1978-01-01

217

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

218

PROBING THE EXCITATION OF EXTREME STARBURSTS: HIGH-RESOLUTION MID-INFRARED SPECTROSCOPY OF BLUE COMPACT DWARFS  

SciTech Connect

We present an analysis of the mid-infrared emission lines for a sample of 12 low-metallicity blue compact dwarf (BCD) galaxies based on high-resolution observations obtained with Infrared Spectrograph on board the Spitzer Space Telescope. We compare our sample with a local sample of typical starburst galaxies and active galactic nuclei (AGNs) to study the ionization field of starbursts over a broad range of physical parameters and examine its difference from the one produced by the AGN. The high-ionization line [O IV]25.89 mum is detected in most of the BCDs, starbursts, and AGNs in our sample. We propose a diagnostic diagram of the line ratios [O IV]25.89 mum/[S III]33.48 mum as a function of [Ne III]15.56 mum/[Ne II]12.81 mum which can be useful in identifying the principal excitation mechanism in a galaxy. Galaxies in this diagram split naturally into two branches. Classic AGNs as well as starburst galaxies with an AGN component populate the upper branch, with stronger AGNs displaying higher [Ne III]/[Ne II] ratios. BCDs and pure starbursts are located in the lower branch. We find that overall the placement of galaxies on this diagram correlates well with their corresponding locations in the log([N II]/Halpha) versus log([O III]/Hbeta) diagnostic diagram, which has been widely used in the optical. The two diagrams provide consistent classifications of the excitation mechanism in a galaxy. On the other hand, the diagram of [Ne III]15.56 mum/[Ne II]12.81 mum versus [S IV]10.51 mum/[S III]18.71 mum is not as efficient in separating AGNs from BCDs and pure starbursts. Our analysis demonstrates that BCDs in general do display higher [Ne III]/[Ne II] and [S IV]/[S III] line ratios than starbursts, with some reaching values even higher than those found at the centers of AGNs. Despite their hard radiation field though, no [Ne V]14.32 mum emission has been detected in the BCDs of our sample.

Hao Lei [University of Texas at Austin, McDonald Observatory, 1 University Station, C1402, Austin, TX 78712-0259 (United States); Wu Yanling [Caltech, Infrared Processing and Analysis Center, MC 314-6, Pasadena, CA 91125 (United States); Charmandaris, V. [University of Crete, Department of Physics, P.O. Box 2208, GR-71003, Heraklion (Greece); Spoon, H. W. W.; Bernard-Salas, J.; Lebouteiller, V.; Houck, J. R. [Cornell University, Astronomy Department, Ithaca, NY 14853-6801 (United States); Devost, D., E-mail: haol@astro.as.utexas.ed [CFHT: Canada France Hawaii Telescope, Kamuela, HI, 96743 (United States)

2009-10-20

219

Probing the Excitation of Extreme Starbursts: High-Resolution Mid-Infrared Spectroscopy of Blue Compact Dwarfs  

NASA Astrophysics Data System (ADS)

We present an analysis of the mid-infrared emission lines for a sample of 12 low-metallicity blue compact dwarf (BCD) galaxies based on high-resolution observations obtained with Infrared Spectrograph on board the Spitzer Space Telescope. We compare our sample with a local sample of typical starburst galaxies and active galactic nuclei (AGNs) to study the ionization field of starbursts over a broad range of physical parameters and examine its difference from the one produced by the AGN. The high-ionization line [O IV]25.89 ?m is detected in most of the BCDs, starbursts, and AGNs in our sample. We propose a diagnostic diagram of the line ratios [O IV]25.89 ?m/[S III]33.48 ?m as a function of [Ne III]15.56 ?m/[Ne II]12.81 ?m which can be useful in identifying the principal excitation mechanism in a galaxy. Galaxies in this diagram split naturally into two branches. Classic AGNs as well as starburst galaxies with an AGN component populate the upper branch, with stronger AGNs displaying higher [Ne III]/[Ne II] ratios. BCDs and pure starbursts are located in the lower branch. We find that overall the placement of galaxies on this diagram correlates well with their corresponding locations in the log([N II]/H?) versus log([O III]/H?) diagnostic diagram, which has been widely used in the optical. The two diagrams provide consistent classifications of the excitation mechanism in a galaxy. On the other hand, the diagram of [Ne III]15.56 ?m/[Ne II]12.81 ?m versus [S IV]10.51 ?m/[S III]18.71 ?m is not as efficient in separating AGNs from BCDs and pure starbursts. Our analysis demonstrates that BCDs in general do display higher [Ne III]/[Ne II] and [S IV]/[S III] line ratios than starbursts, with some reaching values even higher than those found at the centers of AGNs. Despite their hard radiation field though, no [Ne V]14.32 ?m emission has been detected in the BCDs of our sample.

Hao, Lei; Wu, Yanling; Charmandaris, V.; Spoon, H. W. W.; Bernard-Salas, J.; Devost, D.; Lebouteiller, V.; Houck, J. R.

2009-10-01

220

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

221

Do the Infrared Emission Features Need UV Excitation? The PAH Model in UV-poor Reflection Nebulae  

NASA Astrophysics Data System (ADS)

One of the major challenges of identifying the 3.3, 6.2, 7.7, 8.6, and 11.3? m interstellar infrared emission bands with polycyclic aromatic hydrocarbon (PAH) molecules has been the recent detection of these bands in regions with little ultraviolet (UV) illumination since small, neutral PAH molecules have little or no absorption at visible wavelengths and thus are excited primarily by UV photons. The ``astronomical'' PAH model (Li & Draine 2001), incorporating the experimental result that the visual absorption edge shifts to longer wavelength upon ionization and/or as the PAH size increases (Allamandola, Hudgins, & Sandford 1999), is shown to be able to closely reproduce the observed infrared emission bands of vdB 133, a UV-poor reflection nebula (Uchida, Sellgren, & Werner 1998) as well as the 6.2, 7.7, and 11.3? m band ratios of the UV-deficient ring in the Andromeda galaxy M31 (Pagani et al. 1999). It is also shown that ``astronomical'' PAHs can be heated sufficiently by a T eff=3000 K black-body to emit at 6.2, 7.7, 8.6, and 11.3? m. Illustrative mid-IR emission spectra are calculated for reflection nebulae illuminated by cool stars with T eff=3600, 4500, 5000 K. These will allow comparison with future Space Infrared Telescope Facility (SIRTF) observations of vdB 135 (T eff=3600 K), vdB 47 (T eff=4500 K), and vdB 101 (T eff=5000 K) (Houck 2001). This research was supported in part by NASA grant NAG5-7030 and NSF grant AST-9619429. { References:} Allamandola, L.J., Hudgins, D.M., & Sandford, S.A. 1999, ApJ, 511, L115 Houck, J.R. 2001, SIRTF Observations of the Mid IR Features in Reflection Nebulae, {\\sf http://sirtf.caltech.edu/ROC/pid19} Li, A., & Draine, B.T. 2001, ApJ, 554, 778 Pagani, L., et al. 1999, A&A, 351, 447 Uchida, K.I., Sellgren, K., & Werner, M.W. 1998, ApJ, 493, L109

Li, A.; Draine, B. T.

2001-12-01

222

Zn2+-triggered excited-state intramolecular proton transfer: a sensitive probe with near-infrared emission from bis(benzoxazole) derivative.  

PubMed

Near-infrared (NIR) emission can offer distinct advantages for biological applications. A fluorescent sensor, Zinhbo-1, based on bis(benzoxazole) ligand with 2,2'-dipicolylamine (DPA) as receptor, was synthesized. In aqueous solution, Zinhbo-1 demonstrates high sensitivity and selectivity for sensing Zn(2+) with about 10-fold enhancement and nanomolar sensitivity (K(d) = 0.29 nM). Moreover, sensor Zinhbo-1 can detect Zn(2+) in near-infrared region (over 700 nm) with large Stokes shift (ca. 230 nm) attributing to the Zn(2+)-induced excited state intramolecular proton transfer (ESIPT). PMID:21243147

Xu, Yongqian; Pang, Yi

2011-01-18

223

MULTI-PHOTON PHOSPHOR FEASIBILITY RESEARCH  

Microsoft Academic Search

Development of multi-photon phosphor materials for discharge lamps represents a goal that would achieve up to a doubling of discharge (fluorescent) lamp efficacy. This report reviews the existing literature on multi-photon phosphors, identifies obstacles in developing such phosphors, and recommends directions for future research to address these obstacles. To critically examine issues involved in developing a multi-photon phosphor, the project

R. Graham; W. Chow

2003-01-01

224

Population transfer by multiphoton adiabatic rapid passage  

SciTech Connect

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 not all, of the observed phenomena.

Maeda, H.; Gurian, J. H.; Gallagher, T. F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904-0714 (United States) and PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012 (Japan); Department of Physics, University of Virginia, Charlottesville, Virginia 22904-0714 (United States)

2011-03-15

225

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

Microsoft Academic Search

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

Johnson

1991-01-01

226

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

227

Characterization of multiphoton laser scanning device optical parameters for image restoration  

Microsoft Academic Search

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

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

2004-01-01

228

In vivo multiphoton tomography of skin during wound healing and scar formation  

NASA Astrophysics Data System (ADS)

Multiphoton tomography based on femtosecond laser NIR (near infrared) pulses was used to perform non-invasive optical sectioning of skin with high spatial and intracellular resolution. Scar formation due to formation of collagen fibers is an important aspect during wound healing processes in skin and tissues and was monitored in vivo using the system DermaInspect. Multiphoton tomography was performed of a dermal wound after nevi extraction. The healing process and the aggregation of collagen fibers could be long term monitored due to the autofluorescence of endogenous fluorophores and SHG of collagen. The system DermaInspect might become a high resolution diagnostic tool for dermatological diagnostics and monitoring therapeutic effects.

Riemann, Iris; Ehlers, Alexander; LeHarzic, Ronan; Martin, Sven; Reif, Annette; K鰊ig, Karsten

2007-03-01

229

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

PubMed

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

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

2012-03-01

230

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

231

Femtosecond dynamics and multiphoton ionization driven with an intense high order harmonic source  

Microsoft Academic Search

We have constructed a high intensity high order harmonic source delivering ~ 109 extreme ultraviolet photons\\/shot on a gas target and used it to observe multiphoton ionization and conduct femtosecond EUV-pump IR-probe experiments. Following excitation by 20-25 eV photons, we observed that the excited ethylene cation (H2C-CH2)+ experienced isomerization to the ethylidene configuration (HC-CHs)+ in 5025 fs, followed by an

Jeroen van Tilborg; Tom Allison; Travis Wright; Marc Hertlein; Roger Falcone; Yanwei Liu; Hamed Merdji; Ali Belkacem

2009-01-01

232

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

233

Fluorescence lifetime imaging with near-infrared dyes  

NASA Astrophysics Data System (ADS)

Near-infrared (NIR) dyes are used as fluorescence markers in small-animal imaging and in diffuse optical tomography of the human brain. In these applications it is important to know whether the dyes bind to proteins or other tissue constituents, and whether their fluorescence lifetimes depend on the targets they are bound to. Unfortunately, neither the lasers nor the detectors of commonly used confocal and multiphoton laser scanning microscopes allow for excitation and detection of NIR fluorescence. We therefore upgraded existing confocal TCSPC FLIM systems with NIR lasers and NIR sensitive detectors. In multiphoton systems we used the Ti:Sa laser as a one-photon excitation source in combination with an NIR-sensitive detector in the confocal beam path. We tested a number of NIR dyes in biological tissue. Some of them showed clear lifetime changes depending on the tissue structures they are bound to. We therefore believe that NIR FLIM can deliver supplementary information on the tissue constitution and on local biochemical parameters.

Becker, Wolfgang; Shcheslavskiy, Vladislav

2013-02-01

234

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

235

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 (2P1/2) <-- 3s (2S1/2) and 5s (2S1/2) <-- 3p (2P1/2) 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 (2P1/2, 2P3/2) 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

236

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

PubMed Central

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

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

2012-01-01

237

Intermediate state polarization in multiphoton ionization of HCl  

SciTech Connect

The paper presents the detailed theoretical description of the intermediate state polarization and photofragment angular distribution in resonance enhanced multiphoton ionization (REMPI) of molecules and the experimental investigation of these effects in the E {sup 1}{sigma}{sup +} and V {sup 1}{sigma}{sup +} states of HCl populated by two-photon transitions. It is shown that the intermediate state polarization can be characterized by the universal parameter b which is in general a complex number containing information about the symmetry of the two-photon excitation and possible phase shifts. The photofragment angular distribution produced by one- or multiphoton excitation of the polarized intermediate state is presented as a product of the intermediate state axis spatial distribution and the angular distribution of the photofragments from an unpolarized intermediate state. Experiments have been carried out by two complementary methods: REMPI absorption spectroscopy of rotationally resolved (E,v{sup '}=0<-X,v{sup ''}=0) and (V,v{sup '}=12<-X,v{sup ''}=0) transitions and REMPI via the Q(0) and Q(1) rotational transitions followed by three-dimensional ion imaging detection. The values of the parameter b determined from experiment manifest the mostly perpendicular nature of the initial two-photon transition. The experimentally obtained H{sup +} -ion fragment angular distributions produced via the Q(1) rotational transition show good agreement with theoretical prediction.

Chichinin, A. I.; Shternin, P. S.; Goedecke, N.; Kauczok, S.; Maul, C.; Vasyutinskii, O. S.; Gericke, K.-H. [Institut fuer Physikalische und Theoretische Chemie, Technische Universitaet Braunschweig, 38106 Braunschweig (Germany) and Institute of Chemical Kinetics and Combustion, 630090 Novosibirsk (Russian Federation); Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Institut fuer Physikalische und Theoretische Chemie, Technische Universitaet Braunschweig, 38106 Braunschweig (Germany); Institut fuer Physikalische und Theoretische Chemie, Technische Universitaet Braunschweig, 38106 Braunschweig (Germany) and Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Institut fuer Physikalische und Theoretische Chemie, Technische Universitaet Braunschweig, 38106 Braunschweig (Germany)

2006-07-21

238

Superpenetration optical microscopy by iterative multiphoton adaptive compensation technique  

PubMed Central

Biological tissues are rarely transparent, presenting major challenges for deep tissue optical microscopy. The achievable imaging depth is fundamentally limited by wavefront distortions caused by aberration and random scattering. Here, we report an iterative wavefront compensation technique that takes advantage of the nonlinearity of multiphoton signals to determine and compensate for these distortions and to focus light inside deep tissues. Different from conventional adaptive optics methods, this technique can rapidly measure highly complicated wavefront distortions encountered in deep tissue imaging and provide compensations for not only aberration but random scattering. The technique is tested with a variety of highly heterogeneous biological samples including mouse brain tissue, skull, and lymph nodes. We show that high quality three-dimensional imaging can be realized at depths beyond the reach of conventional multiphoton microscopy and adaptive optics methods, albeit over restricted distances for a given correction. Moreover, the required laser excitation power can be greatly reduced in deep tissues, deviating from the power requirement of ballistic light excitation and thus significantly reducing photo damage to the biological tissue.

Tang, Jianyong; Germain, Ronald N.; Cui, Meng

2012-01-01

239

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

240

Determination of the activation energy for unimolecular dissociation of a non-covalent gas-phase peptide: Substrate complex by infrared multiphoton dissociation fourier transform ion cyclotron resonance mass spectrometry  

Microsoft Academic Search

The activation energy for the unimolecular dissociation of a non-covalent supramolecular complex between an Artificial Cationic\\u000a Receptor A ([Gua-Val-Val-Val-Amide]+, in which Gua is guanidiniocarbonyl pyrrole) and an Anionic Tetrapeptide B ([N-Acetyl-Val-Val-Ile-Ala]?) has been determined by measurement of the dissociation rate constant as a function of infrared CO2 laser power density. Singly-charged quasimolecular [A+B+H]+ ions are isolated, stored in a Fourier

Mathias Sch鋐er; Carsten Schmuck; Martin Heil; Helen J. Cooper; Christopher L. Hendrickson; Michael J. Chalmers; Alan G. Marshall

2003-01-01

241

Multiphoton Processes in Systems of Rydberg Atoms.  

National Technical Information Service (NTIS)

Multiphoton nonlinear effects and Raman processes of Rydberg systems (Rydberg atom gas or Rydberg matter) by intense laser fields are considered. Some experiments and basic elements of quantum theory of Rydberg matter are briefly reviewed. A correlation b...

E. A. Manykin

2002-01-01

242

Multiphoton ionization of the magnesium atom  

SciTech Connect

The author investigated the process of multiphoton ionization of the magnesium atom in the radiation field of a neodymium laser based on yttrium-aluminum garnet. The experiments were carried out at the fundamental frequency w = 9345 cm/sup -1/) and the second harmonic (w = 18,790 cm/sup -1/) of the laser radiation. A beam-crossing method involving atomic and laser beams was used and the laser was yttrium-aluminum-garnet operating in a Q-switching mode. The investigations show that both singly and doubly charged ions are formed in multiphoton ionization of the magnesium atom and both resonance and direct processes of multiphoton ionization can occur for single-electron multiphoton ionization in relation to the frequency.

Alimov, D.T.; Bel 'Kovskii, A.N.; Medvedeva, V.K.; Torsunova, M.A.

1986-08-01

243

Resonantly enhanced multiphoton ionization of molecules  

SciTech Connect

During the past two years, attention was focused on single-color and multicolor multiphoton processes in diatomic molecules (H/sub 2/, N/sub 2/). Products of photodissociation reactions were also studied. (DLC)

Dehmer, J.L.; Dehmer, P.M.; Pratt, S.T.

1984-01-01

244

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

245

Noninvasive multiphoton imaging of cardiovascular structures using NIR femtosecond laser scanning microscopy  

Microsoft Academic Search

Near infrared (NIR) femtosecond laser scanning microscopy represents a novel and very promising medical diagnostic imaging technology for non-invasive cross-sectional analysis of living biological tissues. In this study multiphoton imaging has been performed to analyze the structural features of extracellular matrix (ECM) components, e.g. collagen and elastin, of living pulmonary and aortic heart valves. High-resolution autofluorescence and second harmonic generation

Katja Schenke-Layland; Iris Riemann; Ulrich A. Stock; Karsten Konig

2004-01-01

246

Three and four center elimination of HCl in the multiphoton dissociation of halogenated hydrocarbons  

Microsoft Academic Search

Three and four center unimolecular elimination reactions of HCl have been investigated for CHF2Cl, CHFCl2, CH3CCl3, CH3CF2Cl, and CHClCF2 in a molecular beam experiment using infrared multiphoton absorption to energize the molecule. The translational energy distributions obtained in this work show that the average translational energy released to the fragments is around 812 kcal\\/mole, except for the three center elimination

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

1978-01-01

247

Fourier transform ion cyclotron resonance mass spectrometry for the characterisation of kavalactones in the kava plant: elemental formulae confirmation by dual spray accurate mass measurement and structural confirmation by infrared multiphoton dissociation and sustained off-resonance irradiation collision induced dissociation.  

PubMed

Roots and extracts of the kava plant have been used in herbal medicine to treat sleep disturbances, stress and anxiety, although reported cases of liver toxicity led to many countries restricting its sale. The detection of the presence of kava in many medicinal products requires the use of methods capable of identifying the kavalactones with high certainty. Here, we describe the use of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) for the characterisation of six kavalactones (kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin and desmethoxyyangonin) utilising accurate mass measurement for the determination of their elemental formulae and product ion MS (both sustained off-resonance irradiation collision-induced dissociation and infrared multiphoton dissociation (SORI-CID and IRMPD) for structural confirmation. High performance liquid chromatography/FT-ICR-MS with a dual spray system for internal calibration of mass spectra was employed for accurate mass measurement and the determination of elemental formulae of the kavalactones in both standards and a root extract to confirm the presence of the kavalactones in the root powder. Mass accuracy of < 1 ppm was achieved. For structural confirmation, the IRMPD and SORI-CID spectra of the kavalactones in standards and a kava root powder extract were compared. Accurate mass measurement of the product ions was also conducted by external calibration and the elemental formula determined to aid with structural confirmation. The presence of the same fragment ions detected in the standards as in the extract further confirmed the presence of the kavalactones in the kava root powder with high certainty. PMID:17057279

Warburton, Emma; Bristow, Tony

2006-01-01

248

ALMA Detection of the Vibrationally Excited HCN J = 4-3 Emission Line in the AGN-hosting Luminous Infrared Galaxy IRAS 205514250  

NASA Astrophysics Data System (ADS)

We present results from our ALMA Cycle 0 observations, at the frequencies around the HCN, HCO+, and HNC J = 4-3 transition lines, of the luminous infrared galaxy IRAS 205514250 at z = 0.043, which is known to host an energetically important obscured active galactic nucleus (AGN). In addition to the targeted HCN, HCO+, and HNC J = 4-3 emission lines, two additional strong emission lines are seen, which we attribute to H2S and CH3CN(+CCH). The HCN-to-HCO+ J = 4-3 flux ratio (~0.7) is higher than in the other starburst-dominated galaxy (~0.2) observed in our ALMA Cycle 0 program. We tentatively (~5?) detected the vibrationally excited (v 2 = 1) HCN J = 4-3 (l = 1f) emission line, which is important for testing an infrared radiative pumping scenario for HCN. This is the second detection of this molecular transition in external galaxies. The most likely reason for this detection is not only the high flux of this emission line, but also the small molecular line widths observed in this galaxy, suggesting that vibrational excitation of HCN may be relatively common in AGN-hosting galaxies.

Imanishi, Masatoshi; Nakanishi, Kouichiro

2013-10-01

249

Two-photon resonance enhanced multiphoton ionization photoelectron spectroscopy of the SH (SD) radical below and above the lowest ionization threshold  

Microsoft Academic Search

A two-photon resonance enhanced multiphoton ionization spectroscopic study on the mercapto radical is carried out in the one-photon energy region between 258 and 208 nm. Thirteen previously unobserved Rydberg states converging upon the a 1 or b 1 + excited ionic states are reported. Identification and characterization of several states with excitation energies below the lowest ionization limit are performed

J. B. Milan; W. J. Buma; C. A. de Lange

1996-01-01

250

Two-photon resonance enhanced multiphoton ionization photoelectron spectroscopy of the SH (SD) radical below and above the lowest ionization threshold  

Microsoft Academic Search

A two-photon resonance enhanced multiphoton ionization spectroscopic study on the mercapto radical is carried out in the one-photon energy region between 258 and 208 nm. Thirteen previously unobserved Rydberg states converging upon the a 1? or b 1?+ excited ionic states are reported. Identification and characterization of several states with excitation energies below the lowest ionization limit are performed by

J. B. Milan; W. J. Buma; C. A. de Lange

1996-01-01

251

DNA multiphoton absorption generates localized damage for studying repair dynamics in live cells.  

PubMed

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. PMID:22067170

Daddysman, Matthew K; Fecko, Christopher J

2011-11-01

252

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

NASA Astrophysics Data System (ADS)

In this work, we demonstrate the application of multiphoton polarization imaging in resolving the structures in surface stratum corneum and dermal layers of ex-vivo human skin. By varying the excitation and emission polarizations, we characterized the structural features in both Laurdan labeled stratum corneum and dermal fibers. The results presented here have important consequences in bioimaging applications of the skin. Both the mechanics of transdermal drug delivery across the skin and physiological significance of the structural changes of the dermis can be monitored. Our results show that the transition dipoles of Laurdan molecules are preferentially oriented normal to the membrane surface. Furthermore, polarization imaging shows that fibrous structures in the dermis generate emission aligned strongly along the excitation polarization. This work shows that multiphoton polarization imaging can be a powerful method in identifying structural orientations in the skin and other biological structures.

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

2003-12-01

253

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

254

Continuum generation in ultra high numerical aperture fiber with application to multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Nonlinear microscopy benefits from broadband laser sources, enabling efficient excitation of an array of fluorophores, for example. This work demonstrates broadening of a narrow band input pulse (6 nm to 40 nm) centered at 1040 nm with excellent shot-to-shot stability. In a preliminary demonstration, multiphoton imaging with pulses from the fiber is performed. In particular second harmonic imaging of corn starch is performed.

Sayler, Nicholas

255

Observation of the PF2 radical by resonance enhanced multiphoton ionization spectroscopy  

Microsoft Academic Search

We have observed nine new excited electronic states of the PF2 radical in the wave number range 50 00071 000 cm?1 via the two photon resonance enhancements they provide in mass resolved multiphoton ionization spectroscopy. We also report abinitio calculations which yield optimized energies, geometries, and vibrational frequencies for the ground states of PF2 and of the PF+2 ion. Energetic

J. D. Howe; M. N. R. Ashfold; J. W. Hudgens; R. D. Johnson

1994-01-01

256

Observation of the SCI radical by resonance enhanced multiphoton ionisation spectroscopy  

Microsoft Academic Search

We report the first observation of any excited electronic state of the SCI radical. SCI (X 2) radicals are produced by photolysis of SCl2 vapour at near-UV wavelengths around 343 nm, and detected by multiphoton ionisation spectroscopy, resonance enhanced at the two-photon energy by a Rydberg state of 2 electronic symmetry. We suggest that this state derives from an electronic

Jonathan D. Howe; Michael N. R. Ashfold; Ross A. Morgan; Wybren Jan Buma; Jolanda B. Milan; Lange de C. A

1995-01-01

257

Note: Dynamic point spread function for single and multiphoton fluorescence microscopy  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a dynamic point spread function (PSF) for single and multiphoton fluorescence microscopy. The goal is to generate a PSF whose shape and size can be maneuvered from highly localized to elongated one, thereby allowing shallow-to-depth excitation capability during active imaging. The PSF is obtained by utilizing specially designed spatial filter and dynamically altering the filter parameters. We predict potential applications in nanobioimaging and fluorescence microscopy.

Mondal, Partha Pratim; Mandal, Subhra; Diaspro, Alberto

2010-04-01

258

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

259

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

260

Multiphoton nanosurgery in cells and tissues  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) femtosecond laser microscopes enable the user to perform highly precise nanosurgery. Tissue components, cells and single organelles of cells inside tumor-sphaeroids and tissues can be precisely manipulated and optically knocked out without collateral damage. In addition, the monitoring effects of nanosurgery in situ using two photon excitation of auto fluorescence of endogenous fluorophores can be performed quite easily with a sub-cellular resolution. This method may become a useful instrument for nano manipulation and nano-surgery in several fields of life sciences.

Riemann, Iris; Stracke, Frank; Sauer, Daniel; Martin, Sven; K鰊ig, Karsten

2006-03-01

261

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

262

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

SciTech Connect

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

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

2009-10-15

263

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

264

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

PubMed

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

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

2013-09-17

265

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

PubMed Central

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

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

2013-01-01

266

Near-infrared Fourier transform photoluminescence spectrometer with tunable excitation for the study of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

A fast, sensitive, automated Fourier transform (FT) photoluminescence (PL) spectrometer with tunable excitation has been developed for analyzing carbon nanotube suspensions over a wide spectral range. A commercially available spectrometer was modified by the addition of a tunable excitation source, custom collection optics, and computer software to provide control and automated data collection. The apparatus enables excitation from 400 to 1100 nm and detection from 825 to 1700 nm, permitting the analysis of virtually all semiconducting single-walled nanotubes (SWNTs), including those produced by the high pressure carbon monoxide conversion and laser processes. The FT approach provides an excellent combination of high sensitivity and fast measurement. The speed advantage exists because the entire emission spectrum is collected simultaneously, while the sensitivity advantage stems from the high optical throughput. The high sensitivity is demonstrated in the measurement of very dilute SWNT suspensions and the observation of novel spectral features, and the speed is demonstrated by measuring the real-time changes in the SWNT PL during rebundling. This contribution describes the assembly of components, the methods for automating data collection, and the procedures for correcting the wavelength-dependent excitation intensity and the interferometer and detector responses.

McDonald, Timothy J.; Jones, Marcus; Engtrakul, Chaiwat; Ellingson, Randy J.; Rumbles, Garry; Heben, Michael J.

2006-05-01

267

Simultaneous multilayer scanning and detection for multiphoton fluorescence microscopy  

PubMed Central

Fast three-(3D) imaging requires parallel optical slicing of a specimen with an efficient detection scheme. The generation of multiple localized dot-like excitation structures solves the problem of simultaneous slicing multiple specimen layers, but an efficient detection scheme is necessary. Confocal theta detection (detection at 90 to the optical axis) provides a suitable detection platform that is capable of cross-talk-free fluorescence detection from each nanodot (axial dimension ? 150?nm). Additionally, this technique has the unique feature of imaging a specimen at a large working distance with super-resolution capabilities. Polarization studies show distinct field structures for fixed and fluid samples, indicating a non-negligible field-dipole interaction. The realization of the proposed imaging technique will advance and diversify multiphoton fluorescence microscopy for numerous applications in nanobioimaging and optical engineering.

Mondal, Partha Pratim; Diaspro, Alberto

2011-01-01

268

Frequency-multiplexed in vivo multiphoton phosphorescence lifetime microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy (MPM) is widely used in vivo for optical sectioning deep inside scattering tissue. Phosphorescence lifetime imaging microscopy (PLIM) is a powerful technique for obtaining biologically relevant chemical information through F鰎ster resonance energy transfer and phosphorescence quenching. Point-measurement PLIM of phosphorescence quenching probes has recently provided oxygen partial pressure measurements in small rodent brain vasculature identified by high-resolution MPM. However, the maximum fluorescence generation rate, which is inversely proportional to the phosphorescence lifetime, fundamentally limits PLIM pixel rates. Here, we demonstrate experimentally a parallel-excitation/parallel-collection MPM-PLIM system that increases the pixel rate by a factor of 100 compared with conventional configurations, while simultaneously acquiring lifetime and intensity images at depth in vivo. Full-frame, three-dimensional, in vivo PLIM imaging of phosphorescent quenching dye is presented for the first time and defines a new platform for biological and medical imaging.

Howard, Scott S.; Straub, Adam; Horton, Nicholas G.; Kobat, Demirhan; Xu, Chris

2013-01-01

269

Suppression of multiphoton intrashell resonances in Li Rydberg atoms  

SciTech Connect

Multiphoton intrashell transitions in strongly driven Li (n=25) Rydberg atoms are studied experimentally. Orthogonal dc electric and magnetic fields lift the degeneracy of the n shell and define the eccentricity e of the initial coherent elliptic states, which are formed by laser excitation and subsequent adiabatic transformation. The intrashell transitions are driven by a time-harmonic electric field linearly polarized parallel to the major axis of the ellipse. N-photon resonances with N=1-9 are studied as a function of e. All resonances with N{>=}3 are suppressed at certain e values in between 0 and 1. A similar system was analyzed by Yabuzaki et al. [Phys. Rev. A 10, 1955 (1974)] who found a simple pattern of suppressions that applies also for the present experiments. The results of these experimentally confirm that each time N is increased by two, an additional suppression is observed.

Waheed, A. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Higher Education Commission of Pakistan, Islamabad (Pakistan); Fregenal, D. [Centro Atomico Bariloche and Consejo Nacional de Investigaciones Cienticas y Tecnicas. R8402AGP S.C. de Bariloche (Argentina); Frette, O.; Foerre, M.; Hjertaker, B. T.; Preclikova, J. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Horsdal, E. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Pilskog, I. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Laboratoire de Chimie Physique Matiere et Rayonnement, Universite Pierre et Marie Curie, Centre National de la Recherche Scientifique, UMR 7614, 75231 Paris Cedex 05 (France)

2011-06-15

270

Phase Sensitive Demodulation in Multiphoton Microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton laser scanning microscopy offers advantages in depth of penetration into intact samples over other optical sectioning techniques. To achieve these advantages it is necessary to detect the emitted light without spatial filtering. In this nondescanned (nonconfocal) approach, ambient room light can easily contaminate the signal, forcing experiments to be performed in absolute darkness. For multiphoton microscope systems employing mode-locked lasers, signal processing can be used to reduce such problems by taking advantage of the pulsed characteristics of such lasers. Specifically, by recovering fluorescence generated at the mode-locked frequency, interference from stray light and other ambient noise sources can be significantly reduced. This technology can be adapted to existing microscopes by inserting demodulation circuitry between the detector and data collection system. The improvement in signal-to-noise ratio afforded by this approach yields a more robust microscope system and opens the possibility of moving multiphoton microscopy from the research lab to more demanding settings, such as the clinic.

Fisher, Walt G.; Piston, David W.; Wachter, Eric A.

2002-06-01

271

Electronically excited molecules: Reaction kinetics and emission of light: Nanosecond infrared spectroscopy, electronic emission from chemical reactions  

Microsoft Academic Search

A time-resolved IR absorption spectrometer capable of detecting chemical transients on the nanosecond timescale was designed, constructed, and successfully implemented. The spectrometer was used to characterize the vibrational relaxation of an open shell radical species, CF3, produced with excess energy from the photolysis of the parent CF3I compound. The effects of vibrational excitation in the CF3 radical on the reaction

C. B. Moore

1992-01-01

272

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.

K鰊ig, Karsten

2011-02-01

273

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; Sch鋐fer, Eike; Quentin, Ulf; Alexeev, Ilya; Fardel, Romain; Arnold, Craig B.; Schmidt, Michael

2013-06-01

274

Space localization and bound-state population in short-pulse resonant multiphoton ionization  

NASA Astrophysics Data System (ADS)

A numerical analysis using the resolvent-operator method shows that the space and time localization of ionization is in fact the key needed to understand the residual population that is left in the excited state in Stark-induced resonant multiphoton ionization. The two viewpoints recently opposed in the literature [Optics and Photonics News 3, 22 (1992) G. N. Gibson, R. R. Freeman, and T. J. McIllrath] are therefore compatible. However, the excited-state population can easily be destroyed if the resonance intensity or the pulse duration is increased.

Agostini, P.; Dimauro, L. F.

1993-06-01

275

Vacuum ultraviolet and near-infrared excited luminescence properties of Ca3(PO4)2:RE3+, Na+ (RE=Tb, Yb, Er, Tm, and Ho)  

NASA Astrophysics Data System (ADS)

Tb3+, Yb3+, Tm3+, Er3+, and Ho3+ doped Ca3(PO4)2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb3+ content is comparable with that of the commercial Zn2SiO4:Mn2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb3+, Tm3+, Er3+, and Ho3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb3+-Ho3+, Yb3+-Er3+, and Yb3+-Tm3+ in Ca3(PO4)2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb3+-Tm3+-Er3+-Ho3+ in Ca3(PO4)2, in which the cross-relaxation process between Er3+ and Tm3+, producing the 1D2-3F4 transition of Tm3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.

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

2011-08-01

276

Studies on wide-field-of-view multiphoton imaging using the flexible clinical multiphoton tomograph MPTflex  

NASA Astrophysics Data System (ADS)

Multiphoton imaging systems are capable of high-resolution 3-D image acquisition of deep tissue. A first commercially available CE-certified biomedical system for subcelluar resolution of human skin has been launched by JenLab company with the DermaInspectR in 2002. The demand for more flexibility caused the development of the MPTflexR, which provides an increased flexibility and accessibility especially for clinical and cosmetic examinations. However the high resolution of clinical multiphoton tomographs are adherent with a small field-of-view (FOV) of about 360360?m2. Especially time-consuming is the relocation of areas of interest (AOI) like lesions, sweat glands or hair shafts during a multiphoton examination. This limitation can be be overcome by macroscopic large-area (wide-field-ofview) multiphoton tomography, which is tested first within this work.

Weinigel, Martin; Breunig, Hans Georg; Fischer, Peter; Kellner-H鰂er, Marcel; B點kle, Rainer; K鰊ig, Karsten

2012-02-01

277

Selective excitation of coupled CO vibrations on a dissipative Cu(100) surface by shaped infrared laser pulses  

SciTech Connect

In a previous paper [Beyvers et al., J. Chem. Phys. 124, 234706 (2006)], the possibility to mode and state selectively excite various vibrational modes of a CO molecule adsorbed on a dissipative Cu(100) surface by shaped IR pulses was examined. Reduced-dimensionality models with stretching-only coordinates were employed to do so. This model is now extended with the goal to include rotational modes. First, we present an analysis of the bound states of the adsorbed CO molecule in full dimension; i.e., six-dimensional eigenstates are obtained by diagonalizing the six-dimensional Hamiltonian containing the semiempirical potential of Tully et al. [J. Vac. Sci. Technol. A 11, 1914 (1993)]. This is achieved by using a contracted iterative eigensolver based on the coupled two-term Lanczos algorithm with full reorthogonalization. Reduced-dimension subsystem eigenvectors are also computed and then used to study the selective excitation of the molecule in the presence of dissipation within the density matrix formalism for open systems. In the density matrix propagations, up to four degrees of freedom were included, namely, r (the C-O distance), Z (the molecule-surface distance), and {phi} and {theta} (the azimuthal and polar angles of the molecular axis with respect to the surface). Short, intense laser pulses are rationally engineered and further refined with optimal control theory, again with the goal for mode and state selective excitation. Also, IR-laser induced desorption is studied. For the calculations, the previous two-mode (r,Z) dipole surface is extended to include the angular dependence and the model for the coupling of the molecule to the surface electronic degrees of freedom is refined.

Tremblay, Jean Christophe; Beyvers, Stephanie; Saalfrank, Peter [Institut fuer Chemie, Universitaet Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam-Golm (Germany)

2008-05-21

278

Electronically excited molecules: Reaction kinetics and emission of light: Nanosecond infrared spectroscopy, electronic emission from chemical reactions  

NASA Astrophysics Data System (ADS)

A time-resolved IR absorption spectrometer capable of detecting chemical transients on the nanosecond timescale was designed, constructed, and successfully implemented. The spectrometer was used to characterize the vibrational relaxation of an open shell radical species, CF3, produced with excess energy from the photolysis of the parent CF3I compound. The effects of vibrational excitation in the CF3 radical on the reaction CF3 + Br2 yields CF3Br + Br were measured. Broadband data collection techniques were used to monitor the reactive and relaxation pathways simultaneously. The energetic radicals react no faster than the thermalized CF3 and may actually have a lower cross section for reaction. The spectrometer was also used to detect the gas phase absorption spectra of the polyatomic radicals. A thorough investigation into ozone-olefin reactions in a cryogenic matrix environment was completed. It was possible to complex ozone with various olefinic partners through careful control of the matrix deposition process, despite the very low (1-5 kcal/mole) activation energies for the ozonolysis reactions. The ground state complexes were observed to form a charge-transfer (CT) complex upon excitation.

Moore, C. B.

1992-02-01

279

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

280

Laser-induced thermal detachment of hot, large molecular ions under multiphoton-absorption conditions  

NASA Astrophysics Data System (ADS)

We observed the delayed electron detachment induced by multiphoton absorption of hot, zinc phthalocyanine negative ions (C32H16N8Zn-) stored in an electrostatic ion storage ring. To examine the critical parameters and conditions that characterize the delayed processes, we performed a theoretical model simulation employing inferred values for molecular properties and experimentally controlled values of excitation laser energy and fluence. The thermal detachment rate was estimated by applying the detailed balance theory, and the internal energy distribution of the ions after multiphoton absorption was calculated as a function of the ion temperature immediately before laser irradiation. Our model simulation well reproduces the experimental results, and demonstrates that the experimental configuration determines the range of the observed detachment rate, namely the detectable energy window of the stored ions. The parameter dependence of the estimated ion temperature on the molecular properties was also obtained.

Goto, M.; Matsumoto, J.; Shiromaru, H.; Achiba, Y.; Majima, T.; Tanuma, H.; Azuma, T.

2013-03-01

281

Non-invasive evaluation of dermal elastosis by in vivo multiphoton tomography with autofluorescence lifetime measurements.  

PubMed

The non-invasive differentiation of dermal elastic fibres from solar elastosis in vivo is of great interest in dermatologic research, especially for efficacy testing of anti-ageing products. To date, no studies on multiphoton excited fluorescence lifetime characteristics of human elastic fibres and solar elastosis are reported. The goal of the present work was the identification of differential criteria for elastic fibres and solar elastosis by the analysis of fluorescence decay curves acquired by time-correlated single photon counting in vivo multiphoton tomography. For this purpose, fluorescence lifetime measurements (FLIM) were performed with 47 volunteers of different age groups at sun-protected and sun-exposed localizations. Bi-exponential curve fitting was applied to the FLIM data, and characteristic differences between age groups and localizations were found in both relevant fit parameters describing the decay slope. The FLIM analyses have shown that dermal autofluorescence has different lifetimes depending on age and in part on localization. PMID:22151391

Koehler, Martin J; Preller, Anja; Elsner, Peter; K鰊ig, Karsten; Hipler, Uta C; Kaatz, Martin

2012-01-01

282

Ultrafast laser-induced electron emission from multiphoton to optical tunneling  

NASA Astrophysics Data System (ADS)

Based on a time-dependent quantum model, a relation between the onset of the optical tunneling regime and the metal work function is determined. In the multiphoton regime, the number of photons required for absorption is reduced from n=3 (at pulse length ?>20 fs) to n=2 (at ?<8 fs) due to the energy uncertainty principle. The phase of the laser is important for optical tunneling, but is only manifest in the multiphoton regime when the number of laser cycles is close to or less than 1. The effect of the field gradient at the tip can be important when the radius of the tip is 40 nm or smaller. The extension of the model to include nonequilibrium electron distribution due to ultrafast laser excitation is discussed. Comparisons with other models and experimental findings are presented.

Pant, M.; Ang, L. K.

2012-07-01

283

Ab initio study of multiphoton absorption properties of formaldehyde, acetaldehyde, and acetone  

NASA Astrophysics Data System (ADS)

The low-lying Rydberg and intravalence excited states of formaldehyde, acetaldehyde, and acetone, accessed by multiphoton absorption, have been investigated at ab initio level according to quantum electrodynamical formalisms, by utilizing random-phase-approximation vertical transition energies and amplitudes. For all three carbonyls, two-photon spectroscopic properties which could be detected with various experimental arrangements have been reported. For formaldehyde, an exhaustive overview on spectroscopic observables associated with multiphoton absorption is presented. The transition probability coefficients and polarizations ratios for two-, three-, and four-photon single-color absorption from plane polarized, circularly polarized, and unpolarized light have been evaluated. The molecular response to concerted absorption of two and three photons from two laser beams under various polarization conditions has been investigated as a function of the photon energies. An attempt has also been made to estimate the magnitude and direction of the electrochromic changes in two-photon spectroscopic properties brought about by an external static electric field.

Galasso, V.

1990-02-01

284

Route to direct multiphoton multiple ionization  

SciTech Connect

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

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

2011-02-15

285

Nonlinear magic: multiphoton microscopy in the biosciences  

Microsoft Academic Search

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

Warren R Zipfel; Rebecca M Williams; Watt W Webb

2003-01-01

286

Multiphoton wave function after Kerr interaction  

Microsoft Academic Search

The multiphoton wave function after Kerr interaction is obtained analytically for an arbitrary photon number. The wave function is composed of two fundamental functions: the input mode function and the linear response function. The nonlinear effects appearing in this wave function are evaluated quantitatively, revealing the limitations of nonlinear quantum optics theories based on single-mode approximations.

Kazuki Koshino

2008-01-01

287

The Multiphoton Ionization Spectrum of Benzene.  

National Technical Information Service (NTIS)

A resonance seen in the multiphoton ionization spectrum of benzene at 391.4 nm is identified as a two-photon resonance with a bound state at 51,085/cm. This state has probable symmetry singlet E(1g) or singlet E(2g) as indicated by an active e(2g) vibrati...

P. M. Johnson

1976-01-01

288

Evidence for Multi-photon transitions between energy levels in a large Current-Biased Magnesium Diboride Josephson Heterojunction  

NASA Astrophysics Data System (ADS)

When photons are strongly coupled to a quantum system, multiphoton transitions can be observed between two energy levels when the quantum energy of the exciting radiation, multiplied by an integer, matches the level spacing. This phenomenon can be observed in Josephson junction qubits exposed to weak microwave radiation at very low temperatures. At microwave resonance, the transition probability of a junction from superconducting to normal state is enhanced and these are used to map multiphoton transitions. We report observation of single- and multi-photon transitions between ground and first excited states in current-biased MgB2 thin film junctions by applying RF with frequencies between 0.5 and 3 Ghz. These large (up to 0.2mm x 0.3 mm) junctions consist of an MgB2 electrode insulated by native oxide from a lead (Pb) or tin (Sn) counter-electrode, and have areas at least 600 times bigger than Nb junctions previously shown to exhibit multiphoton transitions. The data is consistent with theoretical models of junctions behaving in the quantum limit and show anharmonicity of the junction potential when biased near the critical current.

Ramos, Roberto; Carabello, Steven; Lambert, Joseph; Cunnane, Daniel; Dai, Wenqing; Chen, Ke; Li, Qi; Xi, Xiaoxing

2013-03-01

289

Optical temperature sensor through infrared excited blue upconversion emission in Tm3 +/Yb3 + codoped Y2O3  

NASA Astrophysics Data System (ADS)

An analysis of the intense blue upconversion emission at 476 and 488 nm in Tm3 +/Yb3 + codoped Y2O3 under excitation power density of 86.7 W/cm2 available from a diode laser emitting at 976 nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 476 and 488 nm in this material was recorded in the temperature range from 303 to 753 K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.0035 K- 1. The results imply that Tm3 +/Yb3 + codoped Y2O3 is a potential candidate for the optical temperature sensor.

Li, Dongyu; Wang, Yuxiao; Zhang, Xueru; Yang, Kun; Liu, Lu; Song, Yinglin

2012-04-01

290

Optical thermometry through infrared excited green upconversion emissions in Er3+-Yb3+ codoped Al2O3  

NASA Astrophysics Data System (ADS)

Fluorescence intensity ratio (FIR) variation of green upconversion emissions at 523 and 545 nm in the Er3+-Yb3+ codoped Al2O3 has been studied as a function of temperature using a 978 nm semiconductor laser diode as an excitation source. In the temperature range of 295-973 K, the maximum sensitivity and the temperature revolution derived from the FIR technique are approximately 0.0051 K-1 and 0.3 K, respectively. The Er3+-Yb3+ codoped Al2O3 material with the highest operating temperature up to 973 K, the higher temperature revolution, and the fluorescence efficiency indicated that it is promising for applications in optical high temperature sensor.

Dong, B.; Liu, D. P.; Wang, X. J.; Yang, T.; Miao, S. M.; Li, C. R.

2007-04-01

291

Photoionization of excited molecular states  

SciTech Connect

Rapid advances in laser and detector technologies are making it possible to investigate molecular photophysics and photochemistry in powerful new ways. For example, resonantly enhanced multiphoton ionization (REMPI) measurements, in which the total (or the mass selected) ion current is monitored as a function of laser wavelength, have yielded extensive and often novel information on the spectroscopy of the resonant intermediate states. With the addition of photoelectron spectrometry (PES) to analyze the kinetic energy of the ejected electrons, it is possible to determine the branching ratios into different electronic, vibrational, and rotational levels of the product ion and to focus directly on both the dynamics of the multiphoton ionization process and the photoionization of excited state species. In the present paper, we report several REMPI/PES studies of H/sub 2/ and N/sub 2/. The results reflect both the spectroscopy and the dynamics of photoionization of excited molecular states and are discussed in terms of the selection rules for photoionization and the relative probabilities of photoionization from Rydberg and valence states. In some cases, in accordance with the Franck-Condon principle, the results demonstrate that resonant multiphoton ionization through Rydberg states may be a powerful technique for the production of electronic, vibrational, and rotational state selected ions. However, in other cases, systematic departures from Franck-Condon behavior are observed, which reflect the more subtle dynamics of excited state photoionization.

Dehmer, P.M.; Dehmer, J.L.; Pratt, S.T.

1984-01-01

292

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

293

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

294

Excitation of vibrational mode in an adatom-substrate system under a resonant laser field  

SciTech Connect

We present a general discussion about the excitation of stretch mode and energy transfers in an adatom-substrate system under an infrared resonant laser field. Generally, there are two different mechanisms by which the adatom-substrate bond can be highly excited: the pooling process and the absorption of multi-photon. We find that if the frequency dispersion of the laser is much smaller than the anharmonicity of the selected mode, that is, the laser can be treated as monochromatic, the pooling process is dominant in exciting the stretch mode to high energy states. As the frequency dispersion of the laser increases, the excitation to high energy states by direct photon absorption becomes more and more important. We also find that the dependence of the two mechanisms on frequency are quite different: if the pooling dominates, there is only a single peak in excitation probability; if the photon-absorption dominates, there may be several peaks and the main peak may have a red shift. The hydrogen-covered Si(111) system is used as an example to illustrate our discussion and results. PACS numbers: 68.43.Tj,68.43.Pq,68.35.Ja,33.80.Rv

Ma, Jie [Chinese Academy of Sciences; Wang, Enge [Chinese Academy of Sciences; Zhang, Zhenyu [ORNL; Wu, Biao [Institute of Physics, China and Oak Ridge National Laboratory (ORNL)

2008-01-01

295

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

296

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

297

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

NASA Astrophysics Data System (ADS)

LIME is 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.

2011-07-01

298

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

299

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 E.; White, John G.; Hird, S. N.; Sepsenwol, S.; Malcolm, Graeme P.; Maker, G. T.; Ferguson, Allister I.

1996-05-01

300

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

301

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

PubMed

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

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

2013-08-07

302

Multiphoton adiabatic passage for atom optics applications  

SciTech Connect

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

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

2009-04-15

303

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

304

Advances in multiphoton microscopy for imaging embryos  

PubMed Central

Summary of recent advances Multiphoton imaging is a promising approach for addressing current issues in systems biology and high-content investigation of embryonic development. Recent advances in multiphoton microscopy, including light-sheet illumination, optimized laser scanning, adaptive and label-free strategies, open new and promising opportunities for embryo imaging. However, the literature is often unclear about which microscopy technique is most adapted for achieving specific experimental goals. In this review, we describe and discuss the key concepts of imaging speed, imaging depth, photodamage, and nonlinear contrast mechanisms in the context of recent advances in live embryo imaging. We illustrate the potentials of these new imaging approaches with a selection of recent applications in developmental biology.

Supatto, Willy; Truong, Thai V; Debarre, Delphine; Beaurepaire, Emmanuel

2011-01-01

305

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 function寐clearly 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

306

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

307

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

NASA Astrophysics Data System (ADS)

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

Gainer, Christian F.; Romanowski, Marek

2013-02-01

308

In vivo multiphoton imaging of collagen remodeling after microablative fractional rejuvenation  

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

309

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.

K鰊ig, Karsten; Speicher, Marco; B點kle, Rainer; Reckfort, Julia; McKenzie, Gordon; Welzel, Julia; Koehler, Martin J.; Elsner, Peter; Kaatz, Martin

2010-02-01

310

Resilience of multiphoton entanglement under losses  

SciTech Connect

We analyze the resilience under photon loss of the bipartite entanglement present in multiphoton states produced by parametric down-conversion. The quantification of the entanglement is made possible by a symmetry of the states that persists even under polarization-independent losses. We examine the approach of the states to the set of positive partial transpose states as losses increase, and calculate the relative entropy of entanglement. We find that some bipartite distillable entanglement persists for arbitrarily high losses.

Durkin, Gabriel A. [Centre for Quantum Computation, University of Oxford, Oxford OX1 3PU (United Kingdom); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Simon, Christoph [Centre for Quantum Computation, University of Oxford, Oxford OX1 3PU (United Kingdom); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Laboratoire de Spectrometrie Physique, CNRS et Universite J. Fourier-Grenoble, BP 87, 38402 St. Martin d'Heres (France); Eisert, Jens [Institut fuer Physik, University of Potsdam, D-14469 Potsdam (Germany); Bouwmeester, Dirk [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

2004-12-01

311

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

312

Medium-induced multi-photon radiation  

NASA Astrophysics Data System (ADS)

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

Ma, Hao; Salgado, Carlos A.; Tywoniuk, Konrad

2011-01-01

313

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

314

X-ray-laser interaction with matter and the role of multiphoton ionization: Free-electron-laser studies on neon and helium  

SciTech Connect

At the soft-x-ray free-electron laser FLASH in Hamburg, we have studied multiphoton ionization on neon and helium by ion mass-to-charge spectroscopy. The experiments were performed in a focused beam at 42.8 and 38.4 eV photon energy and irradiance levels up to 10{sup 14} W/cm{sup 2}. Direct, sequential, and resonant two-, three-, and four-photon excitations were investigated by quantitative measurements as a function of the absolute photon intensity. The atomic and ionic photoionization cross sections derived indicate a clear dominance of sequential compared to direct multiphoton processes.

Sorokin, A. A. [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-10587 Berlin (Germany); Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Wellhoefer, M. [Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Bobashev, S. V. [Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Tiedtke, K. [Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22603 Hamburg (Germany); Richter, M. [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-10587 Berlin (Germany)

2007-05-15

315

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.

Hern醤dez, Florencio E.; Belfield, Kevin D.; Cohanoschi, Ion; Balu, Mihaela; Schafer, Katherine J.

2004-10-01

316

Near Infrared and Visible Luminescence from Xerogels Covalently Grafted with Lanthanide [Sm(3+), Yb(3+), Nd(3+), Er(3+), Pr(3+), Ho(3+)] ?-Diketonate Derivatives Using Visible Light Excitation.  

PubMed

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

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

2013-09-24

317

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

318

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

319

Resonant enhanced multiphoton ionization studies in atomic oxygen  

SciTech Connect

In this paper we analyze two-photon-resonant three-photon ionization of atomic oxygen via the 2p/sup 3/(/sup 4/S/sup 0/)np/sup 3/P/sub 0/,1,2, and the 2p/sup 3/(/sup 4/S/sup 0/)nf /sup 3/F/sub 2/,3,4 states. The various atomic parameters required for calculating the resonant enhanced multiphoton ionization (REMPI) probabilities are obtained using quantum-defect theory. The infinite sums over nonresonant states are truncated at a finite number of terms. Our calculated two-photon excitation cross sections agree well with the results of other recent calculations and of experimental measurements. The photoionization cross section is calculated for various electron kinetic energies. The REMPI dynamics is analyzed by solving the density-matrix equations. This framework consistently takes into account the effects of saturation and ac Stark shifts. REMPI probability is seen to be quite sensitive to the initial detuning, the intensity, and the particular resonant state accessed. The photoionization cross sections also imply that due to the rapid falloff of the cross section, two-color REMPI schemes with a lower-frequency ionizing photon would increase the effective REMPI probability.

Dixit, S.N.; Levin, D.A.; McKoy, B.V.

1988-06-01

320

Label-Free Detection of Breast Masses Using Multiphoton Microscopy  

PubMed Central

Histopathology forms the gold standard for the diagnosis of breast cancer. Multiphoton microscopy (MPM) has been proposed to be a potentially powerful adjunct to current histopathological techniques. A label-free imaging based on two- photon excited fluorescence and second-harmonic generation is developed for differentiating normal breast tissues, benign, as well as breast cancer tissues. Human breast biopsies (including human normal breast tissues, benign as well as breast cancer tissues ) that are first imaged (fresh, unfixed, and unstained) with MPM and are then processed for routine H-E histopathology. Our results suggest that the MPM images, obtained from these unprocessed biopsies, can readily distinguish between benign lesions and breast cancers. In the tissues of breast cancers, MPM showed that the tumor cells displayed marked cellular and nuclear pleomorphism. The tumor cells, characterized by irregular size and shape, enlarged nuclei, and increased nuclear-cytoplasmic ratio, infiltrated into disrupted connective tissue, leading to the loss of second-harmonic generation signals. For breast cancer, MPM diagnosis was 100% correct because the tissues of breast cancers did not have second-harmonic generation signals in MPM imaging. On the contrary, in benign breast masses, second-harmonic generation signals could be seen easily in MPM imaging. These observations indicate that MPM could be an important potential tool to provide label-free noninvasive diagnostic impressions that can guide surgeon in biopsy and patient management.

Lu, Jianping; Zhu, Weifeng; Qiu, Jingting; Chen, Jianxin; Xie, Shusen; Zhuo, Shuangmu; Yan, Jun

2013-01-01

321

Label-free detection of breast masses using multiphoton microscopy.  

PubMed

Histopathology forms the gold standard for the diagnosis of breast cancer. Multiphoton microscopy (MPM) has been proposed to be a potentially powerful adjunct to current histopathological techniques. A label-free imaging based on two- photon excited fluorescence and second-harmonic generation is developed for differentiating normal breast tissues, benign, as well as breast cancer tissues. Human breast biopsies (including human normal breast tissues, benign as well as breast cancer tissues ) that are first imaged (fresh, unfixed, and unstained) with MPM and are then processed for routine H-E histopathology. Our results suggest that the MPM images, obtained from these unprocessed biopsies, can readily distinguish between benign lesions and breast cancers. In the tissues of breast cancers, MPM showed that the tumor cells displayed marked cellular and nuclear pleomorphism. The tumor cells, characterized by irregular size and shape, enlarged nuclei, and increased nuclear-cytoplasmic ratio, infiltrated into disrupted connective tissue, leading to the loss of second-harmonic generation signals. For breast cancer, MPM diagnosis was 100% correct because the tissues of breast cancers did not have second-harmonic generation signals in MPM imaging. On the contrary, in benign breast masses, second-harmonic generation signals could be seen easily in MPM imaging. These observations indicate that MPM could be an important potential tool to provide label-free noninvasive diagnostic impressions that can guide surgeon in biopsy and patient management. PMID:23755295

Wu, Xiufeng; Chen, Gang; Lu, Jianping; Zhu, Weifeng; Qiu, Jingting; Chen, Jianxin; Xie, Shusen; Zhuo, Shuangmu; Yan, Jun

2013-06-06

322

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

NASA Astrophysics Data System (ADS)

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

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

1994-09-01

323

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

324

Multiphoton absorption of HF laser photons by molecules containing a hydroxyl group  

NASA Astrophysics Data System (ADS)

Multiphoton absorption (MPA) of HF laser radiation has been studied, as a function of pressure (15 Pa to 1.3 kPa) and fluence (2 mJ/cm2 to 75 J/cm2) for the series: water, methanol, methan-d3-ol, ethanol, and 2,2,2-trifluoroethanol. As the group attached to the -OH is made more complex, the quasicontinuum occurs after fewer excitation steps, and under ''collisionless'' conditions, the same degree of multiphoton excitation is found to require a lower fluence. For water, at pressures between 73 Pa and 1.3 kPa, the cross sections are considerably lower than those for the other molecules, and MPA requires fluences in excess of ~75 J/cm2. The remaining molecules divide into two groups, the ''small'' molecules (CH3OH and CD3OH) and the ''large'' molecules (C2H5OH and CF3CH2OH). For the small molecules at low pressures, the cross sections decrease with increasing fluence, an effect which is thought to be due to anharmonic bottlenecking. As pressure increases, the fluence dependence of the cross sections disappear. For the large molecules, anharmonic bottlenecking appears to be reduced, due to the greater density of states, and cross sections increase with increasing fluence according to the empirical form: ?(E, P)=K'Eb'Pa (where P is pressure, E is fluence and b', a, and K' are constants). The facility of HF laser-induced collisionless multiphoton dissociation of the -OH containing molecules is discussed in light of these results.

McAlpine, Robert D.; Evans, D. K.; McClusky, F. K.

1980-08-01

325

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

326

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

327

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

328

Photoelectron spectroscopy of excited molecular states  

SciTech Connect

Resonance Enhanced Multiphoton Ionization (REMPI), coupled with high-resolution photoelectron spectroscopy, is becoming an important probe of the photoionization dynamics of molecular excited states at a quantum-state specific level. In this paper we will discuss some results of our studies of ionic rotational and vibrational distributions for REMPI of several small molecules such as H{sub 2}, O{sub 2}, NO, OH, and CH which illustrate some dynamically important features of these processes. 25 refs., 6 figs.

McKoy, V.; Braunstein, M.; Rudolph, H.; Stephens, J.A. (California Inst. of Tech., Pasadena, CA (USA). Arthur A. Noyes Lab. of Chemical Physics); Dixit, S.N. (Lawrence Livermore National Lab., CA (USA)); Lynch, D.L. (Nevada Univ., Reno, NV (USA). Dept. of Chemistry)

1989-07-01

329

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

PubMed Central

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

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

2012-01-01

330

4? Confocal Microscope for Multiphoton Optical Sectioning of GaN Film Luminescence  

NASA Astrophysics Data System (ADS)

In the 4? confocal microscope developed by S. W. Hell et al, laser light coherently illuminates both sides of a thin sample through a pair of high-NA objectives, effectively producing a single standing-wave fringe of 2-photon fluorescence excitation with weak side lobes. Developed initially for biological applications, the 4? microscope of Hell et al demonstrated 75 nm axial resolution with 810 nm light. We have constructed a 4? confocal multiphoton microscope for 3d analysis of band-edge/excitonic photoluminescence in thin films. Excitation is with 130 fs pulses from a Ti:sapphire laser. Instrumental features and preliminary tests with rhodamine and GaN and InN films are reported.

Ucer, K. B.; Liang, Difei; Williams, R. T.; Morkoc, H.

2001-08-01

331

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

332

Decoupling excitations in the far-infrared spectra of a {ital c}-axis YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} single crystal  

SciTech Connect

The infrared reflection spectra of a YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} single-crystal 5{times}7-mm{sup 2} surface containing the {ital c} axis have been recorded from 4 K to room temperature. The spectra obtained for different values of {delta} with the same sample show unambiguously that an extra band, coupled with phonons, appears at low frequencies in the superconducting phase. By decoupling this excitation from the other contributions to the dielectric function, we show that the thermal evolution of the extra band follows the expected behavior for the superconducting order parameter. The excitation energy is characteristic of Cooper pairs formation. The residual low-frequency optical conductivity in the superconducting state is discussed. {copyright} {ital 1996 The American Physical Society.}

Lobo, R.P.; Gotor, F.J.; Odier, P.; Gervais, F. [Centre de Recherches sur la Physique des Hautes Temperatures, CNRS, 45071 Orleans, Cedex 2 (France)

1996-01-01

333

Dynamic Multiphoton Imaging: A Live View from Cells to Systems  

NSDL National Science Digital Library

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

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

2005-02-01

334

In vivo quantification of mTHPC fluorescence in skinfold observation chamber using excitation and detection towards the near infrared region  

NASA Astrophysics Data System (ADS)

In this study, a ratiometric quantification method is developed and applied to monitor mesotetra(hydroxyphenyl) chlorin (mTHPC) pharmacokinetics in the rat skin-fold observation chamber. The method employs a combination of dual-wavelength excitation and dual-wavelength detection. The excitation and detection wavelengths were selected in close to NIR. The first excitation wavelength was used to excite the mTHPC and autofluorescence and the second to excite only autofluorescence, so that this could be substracted. Subsequently the difference was divided by the autofluorescence. Since the method applies division of signal with no mTHPC fluorescence, theory suggests on linear dependency of the method on photosensitizer concentration.

Kasc醟ov, Sl醰ka; de Visscher, Sebastiaan; Kruijt, Bastiaan; de Bruijn, Henri雝te S.; van der Ploeg-van den Heuvel, Ang閘ique; Sterenborg, Henricus J. C. M.; Witjes, Max J. H.; Amelink, Arjen; Robinson, Dominic J.

2009-06-01

335

Single-Photon Counting Multicolor Multiphoton Fluorescence Microscope  

Microsoft Academic Search

We present a multicolor multiphoton fluorescence microscope with single-photon counting sensitivity. The system integrates a standard multiphoton fluorescence microscope, an optical grating spectrograph operating in the UV朧is wavelength region, and a 16-anode photomultiplier tube (PMT). The major technical innovation is in the development of a multichannel photon counting card (mC-PhCC) for direct signal collection from multi-anode PMTs. The electronic design

Christof Buehler; Ki H. Kim; Urs Greuter; Nick Schlumpf; Peter T. C. So

2005-01-01

336

Lippmann-Schwinger description of multiphoton ionization  

SciTech Connect

We outline a formalism and develop a computational procedure to treat the process of multiphoton ionization (MPI) of atomic targets in strong laser fields. We treat the MPI process nonperturbatively as a decay phenomenon by solving a coupled set of the integral Lippmann-Schwinger equations. As basic building blocks of the theory, we use a complete set of field-free atomic states, discrete and continuous. This approach should enable us to provide both the total and differential cross sections of MPI of atoms with one and two electrons. As an illustration, we apply the proposed procedure to a simple model of MPI from a square-well potential and to the hydrogen atom.

Ivanov, I.A.; Kheifets, A.S. [Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2005-04-01

337

REVIEW ARTICLE Multiphoton polymerization of hybrid materials  

NASA Astrophysics Data System (ADS)

Multiphoton polymerization has been developed as a direct laser writing technique for the preparation of complex 3D structures with resolution beyond the diffraction limit of light. The combination of two or more hybrid materials with different functionalities in the same system has allowed the preparation of structures with advanced properties and functions. Furthermore, the surface functionalization of the 3D structures opens new avenues for their applications in a variety of nanobiotechnological fields. This paper describes the principles of 2PP and the experimental set-up used for 3D structure fabrication. It also gives an overview of the materials that have been employed in 2PP so far and depicts the perspectives of this technique in the development of new active components.

Farsari, Maria; Vamvakaki, Maria; Chichkov, Boris N.

2010-12-01

338

Near-infrared excitation profile study of surface-enhanced hyper-Raman scattering and surface-enhanced Raman scattering by means of tunable mode-locked Ti: sapphire laser excitation  

Microsoft Academic Search

Excitation profiles of surface-enhanced hyper-Raman scattering (SEHRS) and surface-enhanced Raman scattering (SERS) of crystal violet on colloidal silver were measured using 1 ps Ti:sapphire laser pulses at wavelengths between 750 and 830 nm. Our measurements allowed the direct determination of the ratio between SEHRS and SERS intensities which exhibited a strong dependence on excitation wavelength. The measured variation of this

Katrin Kneipp; Harald Kneipp; Frank Seifert

1995-01-01

339

The Multiphoton Multiple Ionization of Molecules.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. The multiphoton multiple ionization of a number of molecular systems has been studied using the picosecond laser facility at the Rutherford Appleton Laboratory. The laser produced 0.6ps pulses at 600nm, and 6ps at 248nm when used in conjunction with an excimer laser. The focused intensity in each case was >=q10 ^{15}W/cm^2 . A time of flight mass spectrometer designed and built at Reading University was capable of ion kinetic energy measurement, permitting the molecular dissociation dynamics to be investigated. One major question approached concerned the mode of multiphoton ionization of xenon. Specifically, does the ionization proceed in a sequential (single electron) or a collective (many electron) manner? To this end, experiments were performed with the isoelectronic molecule hydrogen iodide. The results, which were interpreted in terms of a Coulomb explosion mechanism, demonstrated the process to be sequential, rather than collective. Similar experiments on the isoelectronic pair, nitrogen and carbon monoxide tended to confirm this conclusion. These molecules were also studied at a number of laser wavelengths and pulse widths. Although the wavelength was found to have a minimal effect, the pulse width was of great importance. The results for hydrogen and deuterium contrasted with these results for other molecules, in that the energies could not be reconciled with a Coulomb explosion mechanism. Rather, dissociative autoionization or neutral dissociation followed by ionization of the atoms were considered to be the dominant processes. Finally, the existence of high energy protons (~eq100eV) from residual hydrocarbons in the vacuum chamber lead to a study of the alkanes from butane to dodecane. At 600nm, 0.6ps pulse width, the fragment energies were found to vary linearly with carbon chain length. At 248nm, 5ps though, only low energy protons were observed, independent of chain length.

Hatherly, P. A.

340

Highly-excited atoms in the electromagnetic field  

Microsoft Academic Search

A review is given of the properties of highly excited atoms placed in an electromagnetic field. The probabilities of bound-bound and bound-free transitions between quasiclassical atomic states, and also approximate selection rules for such transitions, are examined. The properties of the dynamic polarizability of highly excited states of atoms are investigated. Quantum-mechanical ionization mechanisms (multiphoton and tunneling) are discussed for

N B Delone; B P Kra?nov; D L Shepelyanski?

1983-01-01

341

Photon statistics of atomic fluorescence after {pi}-pulse excitation  

SciTech Connect

The photon statistics of atomic fluorescence after {pi}-pulse excitation is investigated in a system in which the input and output ports are connected to an atom. Since spontaneous decay during input pulse excitation occurs, the output pulse generally contains a multiphoton component with a certain probability. We quantitatively evaluate the probability of the output pulse containing multiple photons and determine the conditions for ideal single-photon generation.

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

2010-09-15

342

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

343

Various structural changes in SiO 2 introduced by one-photon excitation with undulator and two-photon excitation with excimer laser  

NASA Astrophysics Data System (ADS)

Excitation at higher energies beyond the ultraviolet (UV) edge (9 eV) in amorphous SiO 2 (a-SiO 2) can be achieved by two-photon process with ArF excimer laser as well as by one-photon process with undulator radiation. Photo-induced phenomena with two kinds of light sources are reported. Frequency decrease of the Si?O stretching vibration in infrared absorption spectrum was observed in the a-SiO 2 by one-photon process with 14.1 eV rays and higher. Frequency decrease can be explained with transition from regular six membered ring (6 Si and 6 O in a loop) to three and four membered rings (3 (4) Si and 3 (4) O in a loop) in a-SiO 2 network. In case of two-photon process with ArF excimer laser, ablation was observed. Threshold fluence 1 J cm -2 is apparently necessary to commence ablation by a single pulse. Ablation introduced with a single pulse above the threshold fluence did not influence stoichiometry of SiO 2. In contrast, for lower fluence below the threshold, the ablation commenced after several pulses accompanied with oxygen loss and ablated thickness increased via a cumulative process. Photo-ablation below the threshold fluence 1 J cm -2 obeyed two-photon excitation process, in contrast, ablation obeyed multi-photon process above the threshold fluence.

Awazu, Koichi

2000-12-01

344

Stepwise multiphoton activation fluorescence reveals a new method of melanin detection.  

PubMed

The stepwise multiphoton activated fluorescence (SMPAF) of melanin, activated by a continuous-wave mode near infrared (NIR) laser, reveals a broad spectrum extending from the visible spectra to the NIR and has potential application for a low-cost, reliable method of detecting melanin. SMPAF images of melanin in mouse hair and skin are compared with conventional multiphoton fluorescence microscopy and confocal reflectance microscopy (CRM). By combining CRM with SMPAF, we can locate melanin reliably. However, we have the added benefit of eliminating background interference from other components inside mouse hair and skin. The melanin SMPAF signal from the mouse hair is a mixture of a two-photon process and a third-order process. The melanin SMPAF emission spectrum is activated by a 1505.9-nm laser light, and the resulting spectrum has a peak at 960 nm. The discovery of the emission peak may lead to a more energy-efficient method of background-free melanin detection with less photo-bleaching. PMID:23291783

Lai, Zhenhua; Kerimo, Josef; Mega, Yair; Dimarzio, Charles A

2013-06-01

345

Preparation of metallo-dielectric photonic crystals by multi-photon direct laser writing  

NASA Astrophysics Data System (ADS)

Metallo-dielectric photonic crystals (MDPCs) can exhibit intriguing and potentially useful optical properties, including ultra-wide photonic bandgaps, engineered thermal emission, and negative refractive index. But access to such materials has been limited by the lack of suitable methods for their preparation. We have developed a route to three-dimensional (3D) MDPCs that involves fabricating a polymeric pre-form by multi-photon direct laser writing and then conformally depositing metal onto the pre-form by electroless metallization. We use the approach to prepare silver- and copper-plated "woodpile" PCs having face-centered tetragonal symmetry and unit-cell period of several micrometers. The resulting 3D metallized structures exhibit mid-infrared reflectance that is consistent with theory and experimental observations obtained for MDPCs prepared by other routes. These data indicate that multi-photon direct laser writing coupled with electroless metallization is a viable route to complex 3D MDPCs of many symmetries and basis sets and provides a path for integrating such structures with other micron-scale optical elements.

Kuebler, Stephen M.; Tal, Amir; Chen, Yun-Sheng

2008-01-01

346

In-vivo observation of cells with a combined high-resolution multiphoton-acoustic scanning microscope.  

PubMed

We present a combined multiphoton-acoustic microscope giving collocated access to the local morphological as well as mechanical properties of living cells. Both methods relay on intrinsic contrast mechanisms and dispense with the need of staining. In the acoustic part of the microscope, a gigahertz ultrasound wave is generated by an acoustic lens and the reflected sound energy is detected by the identical lens in a confocal setup. The achieved lateral resolution is in the range of 1 mum. Contrast in the images arises mainly from the local absorption of sound in the cells related to viscose damping. Additionally, acoustic microscopy can access the sound speed as well as the acoustic impedance of the cell membrane and the cell shape, as it is an intrinsic volume scanning technique. The multiphoton image formation bases on the detection of autofluorescence due to endogenous fluorophores. The nonlinearity of two-photon absorption provides submicron lateral and axial resolution without the need of confocal optical detection. In addition, in the near-IR cell damages are drastically reduced in comparison with direct excitation in the visible or UV. The presented setup was aligned with a dedicated procedure to ensure identical image areas. Combined multiphoton/acoustic images of living myoblast cells are discussed focusing on the reliability of the method. PMID:17380494

Schenkl, Selma; Weiss, Eike C; Stracke, Frank; Sauer, Daniel; Stark, Martin; Riemann, Iris; Lemor, Robert M; K鰊ig, Karsten

2007-05-01

347

Deep-tissue multiphoton fluorescence lifetime microscopy for intravital imaging of protein-protein interactions  

NASA Astrophysics Data System (ADS)

Fluorescent lifetime imaging microscopy (FLIM) has proven to be a valuable tool in beating the Rayleigh criterion for light microscopy by measuring F鰎ster resonance energy transfer (FRET) between two fluorophores. Applying multiphoton FLIM, we previously showed in a human breast cancer cell line that recycling of a membrane receptorgreen fluorescent protein fusion is enhanced concomitantly with the formation of a receptor:protein kinase C ? complex in the endosomal compartment. We have extended this established technique to probe direct protein-protein interactions also in vivo. Therefore, we used various expressible fluorescent tags fused to membrane receptor molecules in order to generate stable two-colour breast carcinoma cell lines via controlled retroviral infection. We used these cell lines for establishing a xenograft tumour model in immune-compromised Nude mice. Using this animal model in conjunction with scanning Ti:Sapphire laser-based two-photon excitation, we established deep-tissue multiphoton FLIM in vivo. For the first time, this novel technique enables us to directly assess donor fluorescence lifetime changes in vivo and we show the application of this method for intravital imaging of direct protein-protein interactions.

Fruhwirth, G. O.; Matthews, D. R.; Brock, A.; Keppler, M.; Vojnovic, B.; Ng, T.; Ameer-Beg, S.

2009-02-01

348

Electronic autoionization and vibrational-state distributions in resonant multiphoton ionization of H/sub 2/  

SciTech Connect

We investigate the effects of electronic autoionization on the vibrationalbranching ratios in resonant multiphoton ionization of H/sub 2/./ital Ab/ /ital initio/ calculations are performed to obtain the vibrational branchingratios for (3+1) resonant-enhanced multiphoton ionization (REMPI) ofH/sub 2/ via the /ital C/ /sup 1//Pi//sub u/ state. Our calculationsinclude the effects of the dissociative/sup 1//Pi//sub g/(1/sigma//sub u/1/pi//sub u/) autoionizing state andproperly account for the interference between the direct and the indirect(autoionization) channels. We find that the direct and indirect amplitudes arecomparable for excitation via the higher (/ital v//sub /ital i///ge/2) vibrationallevels of the /ital C/ state. Autoionization greatly enhances the branchingratios for /Delta//ital v//ne/0 transitions. These calculations underscore thenecessity for a proper treatment of both the direct and indirect contributionsin understanding the REMPI of molecules via autoionizing states.

Dixit, S. N.; Lynch, D. L.; McKoy, B. V.; Hazi, A. U.

1989-08-01

349

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

350

Signatures of isomerization in photodissociation of trans- crotonaldehyde probed by multiphoton ionization mass spectrometry.  

PubMed

We report the observation of new isomerization effects in the UV-photodissociation of trans-crotonaldehyde upon multiphoton excitation by the third harmonic (355 nm) pulses of a Nd:YAG laser. A time-of-flight mass spectrometric analysis reveals formation of acetaldehyde, acetyl, and methoxy radical cations as signatures of isomerization processes. A small segment of the multiphoton ionization spectrum of jet-cooled crotonaldehyde is recorded by tuning the laser frequency around 355 nm. An oxetene type transient intermediate in the ground state has been considered for acetaldehyde formation following a photochemical model suggested earlier (Reguero ; et al. J. Am. Chem. Soc. 1994, 116, 2101-2114) for such compounds. Likewise, for methoxy radical formation, a trans-cis isomerization about the C?C double bond has been considered in a triplet surface. Electron ionization mass spectra of the compound are also recorded by varying the electron kinetic energy in the range 11-70 eV. Ionic fragments in the mass spectra of the two ionization processes are dramatically different. Our suggested mechanisms for isomerization and fragmentation channels are substantiated by density functional theory calculations. Combined experimental and calculated data lead us conclude that isomerization occurs in neutral potential energy surfaces prior to dissociation and photoionization. PMID:23841578

Ghosh, Arup K; Datta, Sayan; Mukhopadhyay, Anamika; Chakraborty, Tapas

2013-07-17

351

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

352

Two-dimensional resonance enhanced multiphoton ionization of HiCl; i = 35, 37: State interactions, photofragmentations and energetics of high energy Rydberg states  

Microsoft Academic Search

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm?1 region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (?? = 0, 1, and 2) and the ion-pair state V(1?+(?? = 0)) for H35Cl and

Kristja磏 Matthi碼sson; Jingming Long; Huasheng Wang; A磄u磗t Kvaran

2011-01-01

353

Two-dimensional resonance enhanced multiphoton ionization of HiCl; i = 35, 37: State interactions, photofragmentations and energetics of high energy Rydberg states  

Microsoft Academic Search

Mass spectra were recorded for (2 + n) resonance enhanced multiphoton ionization (REMPI) of HCl as a function of resonance excitation energy in the 88865-89285 cm-1 region to obtain two-dimensional REMPI data. Band spectra due to two-photon resonance transitions to number of Rydberg states (Omega' = 0, 1, and 2) and the ion-pair state V(1Sigma+(Omega' = 0)) for H35Cl and

Kristj醤 Matth韆sson; Jingming Long; Huasheng Wang; 羐鷖t Kvaran

2011-01-01

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 393415 nm matched benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide(),(anti) (BPDE), the ultimate carcinogenic BaP metabolite. In addition, the 426447 nm band matched the major metabolites 3-hydroxybenzo[a]pyrene (3-OH BaP) and 9-hydroxybenzo[a]pyrene (9-OH BaP); the 458479 nm band corresponded to the secondary metabolite benzo[a]pyrene-3,6-dione (3,6 BPQ); and a peak at 490530 nm matched the parent compound, BaP. Multiphoton spectral analysis also revealed differences in fluorescence intensities between MCF10A and MCF10CA1h cells within three spectral bands: 393415 nm, 426447 nm and 458479 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

Multiphoton microspectroscopy in living plant cells  

Microsoft Academic Search

Microspectroscopic measurements in plant cells are complicated by the presence of dense cellular structures such as the cell wall that causes severe light scattering. In addition, the low penetration depth of the excitation light limits the fluorescence signal originating from deeper cell layers in thick multi-cellular plant preparations when single-photon excitation (SPE) is applied. However, two-photon excitation (TPE) can overcome

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

2003-01-01

356

Caught in the Act: Intravital Multiphoton Microscopy of Host-Pathogen Interactions  

PubMed Central

Intravital multiphoton microscopy provides a unique opportunity to discover and characterize biological phenomena in the natural context of living organisms. Here we provide an overview of multiphoton microscopy with particular attention to its application for studying host-pathogen interactions.

Hickman, Heather D.; Bennink, Jack R.; Yewdell, Jonathan W.

2009-01-01

357

Resonance enhanced multiphoton ionization spectra of molecules and molecular fragments. Annual progress report, March 1992--February 1993  

SciTech Connect

In this report, the author will review the progress made in his studies of ion rotational distributions resulting from resonance enhanced multiphoton ionization of excited electronic states and from single-photon ionization of ground electronic states of jet-cooled molecules by coherent VUV and XUV radiation. To do so he will select a few examples from his studies which serve to highlight his progress and to identify the background and significance of the specific spectral features and systems he has chosen to study.

NONE

1993-12-31

358

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

359

Fluorene-based pi-conjugated oligomers for efficient three-photon excited photoluminescence and lasing.  

PubMed

A novel series of diphenylamino- and 1,2,4-triazole-end-capped, fluorene-based, pi-conjugated oligomers that includes extended oligofluorenes and oligothienylfluorenes has been synthesized by means of the palladium-catalyzed Suzuki cross-coupling of 9,9-dibutyl-7-(diphenylamino)-2-fluorenylboronic acid and the corresponding 1,2,4,-triazole-based aryl halide as a key step. It was demonstrated that efficient two- and three-photon excited photoluminescence and lasing in the blue region are obtained by pumping near-infrared femtosecond lasers on these materials. Although the absorption and emission maxima of the highly fluorescent and extended oligofluorenes reach a saturation limit, there exists an effective conjugation length for an optimum three-photon absorption cross section in the homologous oligofluorene series. On the other hand, the multiphoton excited emission spectrum and lasing wavelength can easily be modified or tuned by an incorporation of thienyl unit(s) into the fluorene-based pi-conjugated core with which exceptionally large three-photon absorption cross sections up to 3.59 x 10(-77) cm6 s2 in the femtosecond regime have been obtained, thereby highlighting the potential of this series of photonic materials. The optimized full width at half-maximum of the cavityless three-photon upconverted blue lasing spectra are sharply narrowed to approximately 6 nm with an efficiency of up to 0.013%. PMID:19774568

Feng, Xin Jiang; Wu, Po Lam; Tam, Hoi Lam; Li, King Fai; Wong, Man Shing; Cheah, Kok Wai

2009-11-01

360

Infrared-active excitations related to the R^3+ ligand-field splitting in RMn2O5 (R=Ho, Dy, Tb)  

NASA Astrophysics Data System (ADS)

Optical transitions between ligand-field split states of R^3+ ions in RMn2O5 multiferroic single crystals have been studied at the phase transitions in the external magnetic field up to 13 T and uniaxial pressure up to 5 kbar. Spectra of the ligand field excitations change significantly in external magnetic field and correlate with the reversal of electric polarization induced by magnetic field. The oscillator strength and selection rules for ligand field excitations change with external uniaxial pressure. We discuss the connection between the ligand field on R^3+ with the magnetism and dielectric properties of this compounds.

Sirenko, A. A.; O'Malley, S. M.; Kang, T. D.; Kahn, K. H.; Carr, C. L.; Mihaly, L.; Park, S.; Cheong, S.-W.

2009-03-01

361

Soliton dynamics in the multiphoton plasma regime  

NASA Astrophysics Data System (ADS)

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.; Combri, Sylvain; Colman, Pierre; Zheng, Jiangjun; de Rossi, Alfredo; Wong, Chee Wei

2013-01-01

362

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

363

Quantum interferences in resonant multiphoton-ionization processes for a strongly coupled atomic system  

NASA Astrophysics Data System (ADS)

The resonant multiphoton-ionization (MPI) processes in a strongly coupled atomic system have been investigated theoretically and experimentally using atomic hydrogen as a test medium. The characteristics are described with a parameter NL: the product of atom density and interaction length. The MPI characteristics exhibit a single-atom behavior revealing an Autler-Townes doublet in the low-NL region. In the high-NL region, the Autler-Townes doublet is suppressed to almost zero. This phenomenon is shown to be due to destructive interference between the excitation channels to the strongly coupled upper states. It is also shown that a narrow Doppler-free MPI peak appears at the split center of the Autler-Townes doublet in the high-NL region as a consequence of the strong coupling and the propagation effect.

Sihombing, R. S. D.; Katsuragawa, M.; Zhang, G. Z.; Hakuta, K.

1996-08-01

364

Hypericin-Mediated Destruction of Collagen Fibers Revealed by Multiphoton Microscopy  

NASA Astrophysics Data System (ADS)

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

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

365

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

366

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

367

Observation of detection-dependent multi-photon coherence times  

NASA Astrophysics Data System (ADS)

The coherence time constitutes one of the most critical parameters that determines whether or not interference is observed in an experiment. For photons, it is traditionally determined by the effective spectral bandwidth of the photon. Here we report on multi-photon interference experiments in which the multi-photon coherence time, defined by the width of the interference signal, depends on the number of interfering photons and on the measurement scheme chosen to detect the particles. A theoretical analysis reveals that all multi-photon interferences with more than two particles feature this dependence, which can be attributed to higher-order effects in the mutual indistinguishability of the particles. As a striking consequence, a single, well-defined many-particle quantum state can exhibit qualitatively different degrees of interference, depending on the chosen observable. Therefore, optimal sensitivity in many-particle quantum interferometry can only be achieved by choosing a suitable detection scheme.

Ra, Young-Sik; Tichy, Malte C.; Lim, Hyang-Tag; Kwon, Osung; Mintert, Florian; Buchleitner, Andreas; Kim, Yoon-Ho

2013-09-01

368

Coherent population transfer by multiphoton adiabatic rapid pasasage  

NASA Astrophysics Data System (ADS)

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 if it is possible to select desired multiphoton transition from the many possible other transitions. In the present study we report observation of population transfer between Rydberg states of atomic Li in the range of n=7090 by high order (>=11) multiphoton adiabatic rapid passage using a frequency chirped microwave pulse. This work has been supported by the NSF. [1] H. Maeda, D.V.L. Norum, and T.F. Gallagher, Science 307, 1757 (2005).

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

2006-05-01

369

Optical Excitation of MOS Interface States.  

National Technical Information Service (NTIS)

MOS interface states have been studied in n-type samples by infrared optical excitation. Infrared light in the wavelength range 5 to 15 micrometers was used to excite only shallow states near the conduction band edge. Thermal background radiation was excl...

M. Schulz K. Blumenstock

1980-01-01

370

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

371

Multiphoton autofluorescence spectral analysis for fungus imaging and identification  

NASA Astrophysics Data System (ADS)

We performed multiphoton imaging on fungi of medical significance. Fungal hyphae and spores of Aspergillus flavus, Micosporum gypseum, Micosoprum canis, Trichophyton rubrum, and Trichophyton tonsurans were found to be strongly autofluorescent but generate less prominent second harmonic signal. The cell wall and septum of fungal hyphae can be easily identified by autofluorescence imaging. We found that fungi of various species have distinct autofluorescence characteristics. Our result shows that the combination of multiphoton imaging and spectral analysis can be used to visualize and identify fungal species. This approach may be developed into an effective diagnostic tool for fungal identification.

Lin, Sung-Jan; Tan, Hsin-Yuan; Kuo, Chien-Jui; Wu, Ruei-Jr; Wang, Shiou-Han; Chen, Wei-Liang; Jee, Shiou-Hwa; Dong, Chen-Yuan

2009-07-01

372

Multiphoton above threshold effects in strong-field fragmentation.  

PubMed

We present a study of multiphoton dissociative ionization from molecules. By solving the time-dependent Schr鰀inger equation for H(2)(+) and projecting the solution onto double continuum scattering states, we observe the correlated electron-nuclear ionization dynamics in detail. We show-for the first time-how multiphoton structure prevails as long as one accounts for the energies of all the fragments. Our current work provides a new avenue to analyze strong-field fragmentation that leads to a deeper understanding of the correlated molecular dynamics. PMID:23215075

Madsen, C B; Anis, F; Madsen, L B; Esry, B D

2012-10-18

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

Hybrid reflecting objectives for functional multiphoton microscopy in turbid media  

PubMed Central

Most multiphoton imaging of biological specimens is performed using microscope objectives optimized for high image quality under wide-field illumination. We present a class of objectives designed de novo without regard for these traditional constraints, driven exclusively by the needs of fast multiphoton imaging in turbid media: the delivery of femtosecond pulses without dispersion and the efficient collection of fluorescence. We model the performance of one such design optimized for a typical brain-imaging setup and show that it can greatly outperform objectives commonly used for this task.

Vucinic, Dejan; Bartol, Thomas M.; Sejnowski, Terrence J.

2010-01-01

375

Multiphoton transitions in a macroscopic quantum two-state system.  

PubMed

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

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

2004-07-15

376

Optical clearing and multiphoton imaging of paraffin-embedded specimens  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

377

Ca 2+ Fluorescence Imaging with Pico and Femtosecond Two-Photon Excitation: Signal and Photodamage  

Microsoft Academic Search

The signal and limitations of calcium florescence imaging using nonresonant multiphoton absorption of near-infrared femto- and picosecond laser pulses were examined. The fluorescence changes of various Ca2+-indicators induced by transient increases of the intradendritic calcium concentration were evaluated by evoking physiological activity in neocortical neurons in rat brain slices. Photodamage was noticeable as irreversible changes in the parameters describing the

Helmut J. Koester; Dagmar Baur; Rainer Uhl; Stefan W. Hell

1999-01-01

378

Multiphoton Coherent Manipulation in Large Spin Qubits  

NASA Astrophysics Data System (ADS)

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

Chiorescu, Irinel

2009-03-01

379

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

380

Resonance enhanced multiphoton ionization spectra of molecules and molecular fragments. Annual technical report  

SciTech Connect

Resonance Enhanced Multiphoton Ionization (REMPI) utilizes pulsed laser radiation to prepare a molecule in an excited state via absorption of one or more photons and to subsequently ionize that state before it can decay. A remarkable feature of REMPI, and one that is very basic to many of its applications and uses, is that the very narrow bandwidth of the {open_quotes}pump{close_quotes} laser makes it possible to select a specific vibrational and rotational level in the initial state and to prepare the excited state of interest in a single vibrational and rotational level. Thus, by suitable choice of the photon pump transition, it is possible to selectively ionize a species of interest without ionizing any other species that might be present. This feature makes REMPI one of the most powerful tools for ultrasensitive detection of species. With REMPI it is also possible to study the photoionization dynamics of a single rotational level of an excited electronic state. Such state-resolved studies can certainly be expected to provide significant insight into the underlying dynamics of molecular photoionization.

NONE

1997-07-01

381

Peak-power dependence of rovibronic populations below the quasicontinuum during IR multiphoton absorption  

SciTech Connect

Experimental studies on IR multiphoton absorption and dissociation have generally provided insight only into the relationship of IR laser characteristics such as power, wavelength, and mode structure to the observables dissociation yields, average number of photons absorbed, and product energy distribution. As a result, theoretical modeling of absorption at levels below the quasicontinuum has been based on facts somewhat removed from the actual phenomenon of interest. The experiments presented here provide information on the unperturbed rotational/vibrational populations of levels subsequent to IR excitation at levels below 4000 cm/sup -1/ of energy. The experiment makes use of molecular beam techniques in conjunction with IR-visible double resonance. A CO/sub 2/ laser of known pulse duration prepares vibrationally excited thiophosgene, Cl/sub 2/C = S. The absorbing transition is 2 ..nu../sub 4/. A tunable nitrogen-pumped dye laser scans the visible excitation spectrum to probe the perturbed rotational-vibrational populations of the pumped mode. Because the electronic transition is electric dipole forbidden, combination hot bands having the appropriate quantum numbers of the ground state are used in the analysis.

Brenner, D M

1981-01-01

382

Analysis of pesticides by gas chromatography/multiphoton ionization/mass spectrometry using a femtosecond laser.  

PubMed

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOFMS) was utilized for analysis of a standard mixture sample containing 49 pesticides and 4 real samples using the third-harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (100 fs) as the ionization source. A sample of a standard mixture of n-alkane was also measured for calibration of the retention time indices of the pesticides. Two photons are required for the excitation of n-alkane due to an absorption band located in the far ultraviolet region (140 nm). The n-alkane molecule in the excited state was subsequently ionized either directly or by absorbing another photon because of a high ionization potential. Due to a large excess of energy, the molecular ion was decomposed and formed many fragment ions. Compared to n-alkanes, most of the pesticides were softly ionized by the femtosecond laser; one photon was used for excitation and another was used for the subsequent ionization. The pesticides with no conjugated double bond had a lower ionization efficiency. The present analytical instrument was applied to several samples prepared from a variety of vegetables and a single fruit after pretreatment with solid-phase extraction. Three pesticides were found in these samples, although some of them were not detected by conventional GC/EI/MS-MS due to insufficient sensitivity and selectivity. PMID:21763808

Li, Adan; Imasaka, Tomoko; Uchimura, Tomohiro; Imasaka, Totaro

2011-06-13

383

Intense red upconversion emission in infrared excited holmium-doped PbGeO 3朠bF 2朇dF 2 transparent glass ceramic  

Microsoft Academic Search

Intense red upconversion emission around 650nm in PbGeO3朠bF2朇dF2 transparent glass ceramic containing ?-PbF2:Ho3+ nanocrystals, is presented. The holmium-doped vitroceramic samples were excited by a 980nm diode laser source. The 650nm upconversion signal was assigned to the 5F5?5I8 transition of holmium ions. Very low intensity signals around 490 and 540nm corresponding to the 5F2,3?5I8 and 4S2,5F4?5I8 transitions, respectively, were also detected.

A. S. Gouveia-Neto; E. B. da Costa; L. A. Bueno; S. J. L. Ribeiro

2004-01-01

384

Vectorizable wave propagation FORTRANcode for calculations of multiphoton dissociation  

Microsoft Academic Search

A vectorizable FORTRAN code for the ETA10 or other vector machines for numerical calculation of the time-dependent Schr鰀inger equation is presented. Preliminary results for the multiphoton dissociation of nitrogen oxide are shown. The applied electric field was approximated by a classical sinusoidal wave; both sinusoidal and cosinusoidal wave forms were tested, and the internuclear potential was taken to be a

Julian J.-L. Ting; J. M. Yuan; T.-F. Jiang

1992-01-01

385

A multiphoton microscope platform for imaging the mouse eye  

PubMed Central

Purpose To demonstrate the ability of multiphoton microscopy to obtain full three-dimensional high-resolution images of the intact mouse eye anterior chamber without need for enucleation. Methods A custom multiphoton microscope was constructed and optimized for deep tissue imaging. Simultaneous two-photon autofluorescence (2PAF) and second harmonic generation (SHG) imaging were performed. A mouse holder and stereotaxic platform were designed to access different parts of the eye for imaging. A reservoir for keeping the eye moist was used during imaging sessions. Results Non-invasive multiphoton images deep inside the anterior chamber of the mouse eye were obtained without the need for enucleation. The iris, corneal epithelium and endothelium, trabecular meshwork region and conjunctiva were visualized by the 2PAF and SHG signals. Identification of the anatomy was achieved by the intrinsic properties of the native tissue without any exogenous labeling. Images as deep as 600 microns into the eye were clearly demonstrated. Full three-dimensional image reconstructions of the entire anterior chamber were performed and analyzed using custom software. Conclusions Multiphoton imaging is a highly promising tool for ophthalmic research. We have demonstrated the ability to image the entire anterior chamber of the mouse eye in its native state. These results provide a foundation for future in vivo studies of the eye.

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

2012-01-01

386

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

387

Squeezing in the Multiphoton Jaynes-Cummings Model.  

National Technical Information Service (NTIS)

Squeezing states in the exactly soluble multiphoton Jaynes-Cummings model, where the atom is initially in the ground state and the fields are in a coherent state, have been obtained. The immediate appearance of squeezing in a/sub 1/ for short times of int...

A. S. Shumovskij L. K. Fam E. I. Aliskenderov

1987-01-01

388

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

389

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

390

Photodissociation of vibrationally excited OH\\/OD radicals  

Microsoft Academic Search

This paper describes a joint experimental and theoretical study of the photodissociation of vibrationally excited hydroxyl radicals. OH and OD radicals produced in a pulsed electric discharge supersonic beam are state-selected and focused by a hexapole and then photo-dissociated by a single laser tuned to various H\\/D or O atom (2 + 1) resonance enhanced multiphoton ionization (REMPI) wavelengths between

Dragana C. Radenovic; Andr J. A. van Roij; Shiou-Min Wu; J. J. Ter Meulen; David H. Parker; Liesbeth M. C. Janssen; Gerrit C. Groenenboom

2008-01-01

391

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 (?2.410-3 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., B躌GER, 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., MARGUL萐, 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.; B黵ger, H.; Demaison, J.; Willaert, F.; M鋎er, H.; Larsen, N. W.

392

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

SciTech Connect

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

Marcos Dantus

2008-09-23

393

Molecular Dynamics in Living Cells Observed by Fluorescence Correlation Spectroscopy with One and Two-Photon Excitation  

Microsoft Academic Search

Multiphoton excitation (MPE) of fluorescent probes has become an attractive alternative in biological applications of laser scanning microscopy because many problems encountered in spectroscopic measurements of living tissue such as light scattering, autofluorescence, and photodamage can be reduced. The present study investigates the characteristics of two-photon excitation (2PE) in comparison with confocal one-photon excitation (1PE) for intracellular applications of fluorescence

Petra Schwille; Ulrich Haupts; Sudipta Maiti; Watt W. Webb

1999-01-01

394

N-H stretching excitations in adenosine-thymidine base pairs in solution: pair geometries, infrared line shapes, and ultrafast vibrational dynamics.  

PubMed

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

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

2013-01-07

395

Infrared Dye Laser Study.  

National Technical Information Service (NTIS)

Near infrared laser action has been demonstrated for 9 Kodak organic dyes, using a linear flash lamp for excitation. The spectral region covered by these 9 dyes extends from 850 nm to at least 960 nm, with no tuning attempted so far. Output is in the kilo...

B. E. Plourde J. P. Webb

1972-01-01

396

Infrared Dye Laser Study.  

National Technical Information Service (NTIS)

Building on work done in Phase I of this study (See AD-748 863), research on near-infrared dye lasers continued along several lines. Eighteen more Kodak organic dyes were screened for laser action using a linear flash lamp for excitation. Six dyes lased b...

B. E. Plourde J. P. Webb

1973-01-01

397

Infrared Astronomy  

NSDL National Science Digital Library

NASA's Infrared Processing and Analysis Center (IPAC) provides the Infrared Astronomy Website as one of its outreach programs. Infrared Astronomy, or "the detection and study of the infrared radiation (heat energy) emitted from objects in the Universe," is described and placed in context in the sections Discovery of Infrared, What is Infrared, Infrared Astronomy, Background, and the Infrared Universe. For current information, see the News & Discoveries, Active/ Future Projects, and Activities sections; past and current projects supported by IPAC are featured in the Infrared Gallery. The site targets a broad audience and is geared towards many learning levels.

398

REVIEWS OF TOPICAL PROBLEMS: Highly-excited atoms in the electromagnetic field  

Microsoft Academic Search

A review is given of the properties of highly excited atoms placed in an electromagnetic field. The probabilities of bound-bound and bound-free transitions between quasiclassical atomic states, and also approximate selection rules for such transitions, are examined. The properties of the dynamic polarizability of highly excited states of atoms are investigated. Quantum-mechanical ionization mechanisms (multiphoton and tunneling) are discussed for

N. B. Delone; B. P. Krainov; D. L. Shepelyanskii

1983-01-01

399

Multiphoton spectral microscopy for imaging and quantification of tissue glycation  

PubMed Central

Tissue glycation from diabetes and aging can result in complications such as renal failure, blindness, nerve damage and vascular diseases. In this work, we applied multiphoton microscopy for imaging and characterizing the extent of tissue glycation. The characteristic features of multiphoton autofluorescence (MPAF) and second harmonic generation (SHG) images as well as MPAF spectra of glycated bovine skin, cornea and aorta were acquired. The analysis of MPAF intensity change accompanying the glycation process shows that collagen is more responsive to the formation of autofluorescent advanced glycation endproducts (AGE) than elastic fibers. Changes in spectral features were also used to estimate the rate of glycation in tissues with intrinsic AF. Our study shows that multiphton imaging may be used for the in vitro investigation of the effects of tissue glycation and that this approach may be used for monitoring AGE formation in the clinical setting.

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

2011-01-01

400

Multiphoton Imaging of Ultrasound Bioeffects in the Murine Brain  

NASA Astrophysics Data System (ADS)

The purpose of this study was to demonstrate the feasibility of multiphoton imaging in the murine brain during exposure to ultrasound. Our experimental setup coupled ultrasound through the ventral surface of the mouse while allowing imaging through a cranial window from the dorsal surface. Field attenuation was estimated by scanning the field after insertion of a freshly sacrificed mouse; beam profile and peak position were preserved, suggesting adequate targeting for imaging experiments. C57 mice were imaged with a Biorad multiphoton microscope while being exposed to ultrasound (f = 1.029 MHz, peak pressure ~ 200 kPa, average power ~ 0.18 W) with IV injection of Optison. We observed strong vasoconstriction coincident with US and Optison, as well as permeabilization of the blood-brain barrier.

Raymond, Scott; Skoch, Jesse; Bacskai, Brian; Hynynen, Kullervo

2006-05-01

401

Waveguide characterization with multi-photon photoemission electron microscopy  

NASA Astrophysics Data System (ADS)

Multi-photon photoemission electron microscopy (PEEM) images surface interactions of visible light with matter, showing electromagnetic (EM) waves that propagate at or near the surface. Images are interferometric, showing where incident and surface waves are in-phase (bright) and out-of-phase (dark), with strong contrast between regions of high and low rates of photoelectron emission. Interferogram analysis can determine the amplitude, wavelength, phase evolution, and propagation decay length of the surface waves. Most multi-photon PEEM studies focus on surface plasmon polaritons. We show that this technique can also be applied to conducting thin-film waveguides, measuring the properties of confined EM waves in a two-mode slab waveguide made of indium tin oxide on glass, which are consistent with waveguide theory. This research was funded by the US Department of Energy Basic Science Office under contract DE-FG02-10ER46406.

Fitzgerald, J. P. S.; Word, Robert C.; Saliba, Sebastian; Koenenkamp, Rolf

2012-10-01

402

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

403

High-order multiphoton ionization photoelectron spectroscopy of NO  

SciTech Connect

Photoelectron energy and angular distributions of NO following three different high-order multiphoton ionization (MPI) schemes have been measured. The 3+3 resonantly enhanced multiphoton ionization (REMPI) via the A{sup 2}{Sigma}{sup +} (v=0) level yielded a distribution of electron energies corresponding to all accessible vibrational levels ({ital v}{sup +}=0--6) of the nascent ion. Angular distributions of electrons corresponding to {ital v}{sup +}=0 and {ital v}{sup +}=3 were significantly different. The 3+2 REMPI via the A{sup 2}{Sigma}{sup +} ({ital v}=1) level produced only one low-energy electron peak ({ital v}{sup +}=1). Nonresonant MPI at 532 nm yielded a distribution of electron energies corresponding to both four- and five-photon ionization. Prominent peaks in the five-photon photoelectron spectrum (PES) suggest contributions from near-resonant states at the three-photon level.

Carman, H.S. Jr.; Compton, R.N. (Chemical Physics Section, Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, Tennessee 37831-6125 (US)) Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996 (US))

1988-10-01

404

High-order multiphoton ionization photoelectron spectroscopy of NO  

SciTech Connect

Photoelectron energy angular distributions of NO following three different high-order multiphoton ionization (MPI) schemes have been measured. The 3 + 3 resonantly enhanced multiphoton ionization (REMPI) via the A/sup 2/..sigma../sup +/ (v=O) level yielded a distribution of electron energies corresponding to all accessible vibrational levels (v/sup +/=O-6) of the nascent ion. Angular distributions of electrons corresponding to v/sup +/=O and v/sup +/=3 were significantly different. The 3 + 2 REMPI via the A/sup 2/..sigma../sup +/ (v=1) level produced only one low-energy electron peak (v/sup +/=1). Nonresonant MPI at 532 nm yielded a distribution of electron energies corresponding to both four- and five-photon ionization. Prominent peaks in the five-photon photoelectron spectrum (PES) suggest contributions from near-resonant states at the three-photon level. 4 refs., 3 figs.

Carman, H.S. Jr.; Compton, R.N.

1987-01-01

405

Cryogenic exciter  

SciTech Connect

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

406

Vectorizable wave propagation FORTRANcode for calculations of multiphoton dissociation  

NASA Astrophysics Data System (ADS)

A vectorizable FORTRAN code for the ETA10 or other vector machines for numerical calculation of the time-dependent Schr鰀inger equation is presented. Preliminary results for the multiphoton dissociation of nitrogen oxide are shown. The applied electric field was approximated by a classical sinusoidal wave; both sinusoidal and cosinusoidal wave forms were tested, and the internuclear potential was taken to be a Morse function. Dissociation histories of three types were found.

Ting, Julian J.-L.; Yuan, J. M.; Jiang, T.-F.

1992-06-01

407

Generating four-mode multiphoton entangled states in cavity QED  

SciTech Connect

We propose a scheme to generate four-mode multiphoton entangled states by passing N identical atoms through two high-Q cavities in turn. In the case of N=1, the scheme can deterministically generate Einstein-Podosky-Rosen entangled photon pairs. We use adiabatical state evolution under large atom-cavity detuning, so the scheme is insensitive to atomic spontaneous decay. The influence of cavity decay on fidelity and success probability is also discussed.

Shu Jing; Zou Xubo; Xiao Yunfeng; Guo Guangcan [Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026 (China)

2006-10-15

408

Quantum Decoherence for Multi-Photon Entangled States  

Microsoft Academic Search

We investigate quantum decoherence of the multi-photon entangled state |psiNmrangle = Script Nm[cos gamma|N-mrangle1|mrangle2+eithetamsin gamma|mrangle1|N-mrangle2]. When the entangled channel |psiNmrangle is embedded in an environment, the channel decoheres and becomes a mixed state governed by a master equation. We calculate the linear entropy and the relative entropy of entanglement, which describe the mixedness and the amount of entanglement for the

Yan-Hua Sun; Xia Zhu; Le-Man Kuang

2005-01-01

409

Resonant multiphoton optogalvanic detection of atomic hydrogen in flames.  

PubMed

Atomic hydrogen has been studied in an atmospheric-pressure hydrogen-air flame by using resonant multiphoton optogalvanic spectroscopy. This technique offers excellent spatial and temporal resolution, with an estimated sensitivity at the 1-part-in-10(6) level. This experiment represents the first reported direct, in situ optical detection of the extremely important hydrogen radical in a combustion environment. PMID:19714048

Goldsmith, J E

1982-09-01

410

Optical temperature sensing of NaYbF4: Tm3+ @ SiO2 core-shell micro-particles induced by infrared excitation.  

PubMed

NaYbF4:Tm3+@SiO2 core-shell micro-particles were synthesized by a hydrothermal method and subsequent ultrasonic coating process. Optical temperature sensing has been observed in NaYbF4: Tm3+@SiO2 core-shell micro-particles with a 980 nm infrared laser as excitation source. The fluorescence intensity ratios, optical temperature sensitivity, and temperature dependent population re-distribution ability from the thermally coupled 1D2 /1G4 and 3F2 /3H4 levels of the Tm3+ ion have been analyzed as a function of temperature in the range of 100~700 K in order to check its availability as a optical temperature sensor. A better behavior as a low-temperature sensor has been obtained with a minimum sensitivity of 5.4 10-4 K-1 at 430 K. It exhibits temperature induced population re-distribution from 1D2 /1G4 thermally coupled levels at higher temperature range. PMID:24104034

Wang, Xiangfu; Zheng, Jin; Xuan, Yan; Yan, Xiaohong

2013-09-01

411

Human hepatocellular carcinoma diagnosis by multiphoton autofluorescence microscopy  

NASA Astrophysics Data System (ADS)

Conventionally, the diagnosis of hepatocellular carcinoma (HCC) is performed by qualitative examination of histopathological specimens, which takes times for sample preparation in fixation, section and stain. Our objective is to demonstrate an effective and efficient approach to apply multiphoton microscopy imaging the HCC specimens, with the advantages of being optical section, label-free, subcellular resolution, minimal invasiveness, and the acquisition of quantitative information at the same time. The imaging modality of multiphoton autofluorescence (MAF) was used for the qualitative imaging and quantitative analysis of HCC of different grades under ex-vivo, label-free conditions. We found that while MAF is effective in identifying cellular architecture in the liver specimens, and obtained quantitative parameters in characterizing the disease. Our results demonstrates the capability of using tissue quantitative parameters of multiphoton autofluorescence (MAF), the nuclear number density (NND), and nuclear-cytoplasmic ratio (NCR) for tumor discrimination and that this technology has the potential in clinical diagnosis of HCC and the in-vivo investigation of liver tumor development in animal models.

Sun, Tzu-Lin; Liu, Yuan; Sung, Ming-Chin; Chen, Hsiao-Ching; Yang, Chuen-Huei; Hovhannisyan, Vladimir; Chiou, Ling-Ling; Lin, Wei-Chou; Huang, Guan-Tarn; Kim, Ki-Hean; So, Peter T. C.; Lin, Chih-Ju; Lee, Hsuan-Shu; Dong, Chen-Yuan

2010-02-01

412

Multiphoton microscopy of engineered dermal substitutes: assessment of 3-D collagen matrix remodeling induced by fibroblast contraction  

NASA Astrophysics Data System (ADS)

Dermal fibroblasts are responsible for the generation of mechanical forces within their surrounding extracellular matrix and can be potentially targeted by anti-aging ingredients. Investigation of the modulation of fibroblast contraction by these ingredients requires the implementation of three-dimensional in situ imaging methodologies. We use multiphoton microscopy to visualize unstained engineered dermal tissue by combining second-harmonic generation that reveals specifically fibrillar collagen and two-photon excited fluorescence from endogenous cellular chromophores. We study the fibroblast-induced reorganization of the collagen matrix and quantitatively evaluate the effect of Y-27632, a RhoA-kinase inhibitor, on dermal substitute contraction. We observe that collagen fibrils rearrange around fibroblasts with increasing density in control samples, whereas collagen fibrils show no remodeling in the samples containing the RhoA-kinase inhibitor. Moreover, we show that the inhibitory effects are reversible. Our study demonstrates the relevance of multiphoton microscopy to visualize three-dimensional remodeling of the extracellular matrix induced by fibroblast contraction or other processes.

Pena, Ana-Maria; Fagot, Dominique; Olive, Christian; Michelet, Jean-Fran鏾is; Galey, Jean-Baptiste; Leroy, Fr閐閞ic; Beaurepaire, Emmanuel; Martin, Jean-Louis; Colonna, Anne; Schanne-Klein, Marie-Claire

2010-09-01

413

Infrared vibrational spectra of tert-butyl halides in dehydrated sodium-X and low-aluminum hydrogen-Y faujasites; vibrational excitation exchange and other effects of guest-host interactions  

NASA Astrophysics Data System (ADS)

Experimental, analytical and modeling techniques employed in this study elucidate interactions between adsorbate molecules and the interior surfaces of the porous faujasites (FAU). The vibrational spectroscopy of guest and host offers opportunities to locate the guest site in the host that can otherwise be approached only with low-temperature x-ray and neutron diffraction studies. Fourier transform infrared (FTIR) studies at 295 K of sodium X-type FAU (Na-X, Si/Al = 1.34, NaxSi(192-x)AlxO384) and low-aluminum acidic Y-type FAU (LAHY, Si/Al = 40, HxSi (192-x)AlxO384) supercage-included tert -butyl halides (CH3)3C-X (X = Cl, Br, I) are presented in comparison with the adsorbate molecular gas-phase and unloaded host solid-state spectra. For both FAU formula x = 1921+Si/Al . In the Na-X studies, four observations of tert-butyl halide (TBH) vibrational band changes (nu5, nu6, nu 7, and {nu3, nu16, nu17}, three of them concomitant with Na-X mode changes, together with computational modeling studies, point to a particular preferred siting of TBH at host hexagonal prisms (D6R). The siting involves simultaneous interactions of the host with methyl group axial protons and the halide atom. All three methyl group axial protons interact preferentially with a single D6R oxygen atom (type O1) via C-H贩稯 bonding. The TBH halide atom interacts with a site III' Na cation. In addition, an exchange of quanta of vibrational excitation between TBH C-X stretching/CH 3 rocking skeletal mode nu5 and the Na-X Si-O-Si antisymmetric stretching band is observed. Analysis of the coalesced band is consistent with an interaction model involving one guest and one host mode. In the isostructural LAHY material, where cation-guest interactions are effectively absent, the weaker interactions of TBH with LAHY framework oxygen atoms are manifest in additional propensity toward the exchange of vibrational excitation quanta between both guest and host modes, and between two guest modes. In contrast to the Na-X results, the LAHY results reveal that guest-host vibrational excitation exchange is taking place between a single guest mode and multiple modes within a particular host band. This type of exchange phenomenon is observed for three different LAHY infrared bands. For both faujasite materials, the IR frequency shifts, exchange phenomena, pseudo-hydrogen bonding effects, and computational modeling studies are related to the siting of the guest molecules in the host supercages, and to the guest-host interactions at the guest sites.

Fox, Jack David

414

The multiphoton ultraviolet and visible upconversion luminescence of ZBLAN material  

NASA Astrophysics Data System (ADS)

The multiphoton ultraviolet and visible upconversion luminescence of Tm3+Yb3+ codoped ZBLAN fluoride glass as excited by a 975nm diode laser was studied. Two typical ultraviolet 290.6nm 1I6 --> 3H6 and 362.0nm 1D2 --> 3H6 upconversion luminescence lines were found. The careful measurement of the variation of upconversion luminescence intensity F as a function of the 975nm pumping laser power P has proven that the 290.6nm 1I6 --> 3H6 and 362.0nm 1D2 --> 3H6 upconversion luminescences are a six-photon and a five-photon upconversion luminescence respectively. Several visible upconversion luminescence lines at 450.5nm, 473.9nm, 648.5nm, (687.3nm, 696.2nm) and (793.5nm, 800.7nm) were found also, which result from the fluorescence transitions of 1D2 --> 3F4, 1G4 --> 3H6, 1G4 --> 3F4, 3F3 --> 3H6 and 3H4 --> 3H6 of Tm3+ ion respectively. It has been proved that the upconversion luminescence of 1G4 state is a three-photon upconversion process, while that of 3F3 or 3H4 state is a two-photon upconversion process. The theoretical analysis suggests that the upconversion mechanism of the 362.0nm 1D2 --> Tm3+ upconversion luminescence is the cross energy transfer of {3H4(Tm3+) --> 3F4(Tm3+), 1G4(Tm3+) --> 1D2(Tm3+)} and {1G4(Tm3+) --> 3F4(Tm3+), 3H4(Tm3+) --> 1D2(Tm3+)} between Tm3+ ions, whereas the mechanism of the 290.6nm 1I6 --> 3H6 upconversion luminescence is the sequential energy transfer of {2F5/2(Yb3+) --> 2F7/2(Yb3+), 1D2(Tm3+) --> 3P1(Tm3+)} and {2F5/2(Yb3+) --> 2F7/2(Yb3+), 1D2(Tm3+) --> 3P2(Tm3+)} from Yb3+ ions to Tm3+ ions. In addition, the upconversion luminescence of G4 and 3H4 state also results from the sequential energy transfer {2F5/2(Yb3+) --> 2F7/2(Yb3+), 3H4(Tm3+) --> 1G4(Tm3+)} and {2F5/2(Yb3+) --> 2F7/2(Yb3+), 3F4(Tm3+) --> 3F2(Tm3+)} from Yb3+ ions to Tm3+ ions respectively.

Chen, Xiaobo; Song, Zengfu; Wang, Yafei; Xiong, Jun; Yang, Guojiian; Li, Song; Zhou, Jing; Peng, Fanglin; Zhou, Gu

2008-03-01

415

A multimodal multiphoton microscope for biological imaging  

NASA Astrophysics Data System (ADS)

We report on the construction of a highly flexible system for advanced biological imaging, where all the following imaging techniques are integrated into the same microscope: Coherent anti-Stokes Raman scattering (CARS), two photon excitation fluorescence (TPEF), second harmonic generation (SGH), sum frequency generation (SFG), fluorescence lifetime imaging (FLIM) and differential interference contrast (DIC). The system employs a Nd:YVO4 laser as pump (7 ps, 1064 nm), and two tunable OPOs (6 ps, 700 - 1000 nm). Our microscope comprises a heater stage and perfusion cell for imaging of live cells, and features an atomic force microscope (AFM) which enables optical imaging at 10 nm resolution. Multimodal imaging of breast cancer cells and tissue will be demonstrated as well as imaging of anticancer drugs in living cells.

Mouras, Rabah; Downes, Andrew; Rischitor, Grigore; Mari, Meropi; Elfick, Alistair

2010-02-01

416

Systematic study of the stable states of C-, Si-, Ge-, and Sn- via infrared laser spectroscopy  

NASA Astrophysics Data System (ADS)

The bound excited np3 2D terms of Si-, Ge-, and Sn- have been investigated with a combination of single- and multiphoton tunable infrared laser experiments. The binding energies of the two J=3/2 and J=5/2 fine-structure levels were found to be 0.527 234(25) and 0.525 489(20) eV, respectively for Si-, 0.401 44(10) and 0.377 27(6) eV for Ge-, and 0.397 617(15) and 0.304 635(15) eV for Sn-. These results constitute improvements in accuracy over previous experimental term energies of up to four orders of magnitude and further provide experimental values for the 2D fine-structure splittings: 14.08(20), 192.6(9), and 749.95(15) cm-1 for Si-, Ge-, and Sn-, respectively. In addition, the photodetachment thresholds of the ionic 4S3/2 ground states have been reinvestigated. This resulted in improved electron affinities of 1.262 119(20), 1.389 521(20), 1.232 712(15), and 1.112 067(15) eV for C-, Si-, Ge-, and Sn-, respectively. Various attempts towards an observation of the very weakly bound C-(2D) and Si-(2P) terms remain unsuccessful.

Scheer, Michael; Bilodeau, Ren C.; Brodie, Cicely A.; Haugen, Harold K.

1998-10-01

417

Two-Photon-Excited Fluorescence Imaging of Human RPE Cells with a Femtosecond Ti:Sapphire Laser  

Microsoft Academic Search

METHODS. Ex vivo TPEF imaging of the human retinal pigment epithelium (RPE) of human donor eyes was conducted with a multiphoton laser scanning microscope that employs a femto- second Ti:sapphire laser as an excitation laser source. The spectrum of autofluorescence of LF granules was analyzed with a confocal laser scanning microscope coupled to a UV argon laser. RESULTS. TPEF examination

Almut Bindewald-Wittich; Meng Han; Steffen Schmitz-Valckenberg; Sarah R. Snyder; Gunter Giese; Josef F. Bille; Frank G. Holz

2006-01-01

418

Resonance enhanced multiphoton and single-photon ionization of molecules and molecular fragments. Annual technical report, May 1, 1994--April 30, 1995  

SciTech Connect

In resonance enhanced multiphoton ionization (REMPI) pulsed laser radiation is utilized to prepare a molecule in an excited state via absorption of one or more photons and to subsequently ionize that level before it decays. A remarkable feature of REMPI is that the very narrow bandwidth of laser radiation makes is possible to select a specific rotational level in the initial (ground) state and to prepare the excited state of interest in a single rotational level. By suitable choice of the excitation step, it is thus possible to selectively ionize a species of interest present in very minor concentrations without ionizing any other species that may be present. This feature makes REMPI a very powerful tool for ultrasensitive detection of trace or transient species.

McKoy, V.

1997-07-01

419

Infrared Investigations.  

ERIC Educational Resources Information Center

|Describes a series of simple and nontraditional experiments that enable students to discover the properties of infrared radiation by studying the propagation, reflection, diffusion, and refraction of infrared. The experiments rely on two modules, an infrared transmitter and an infrared receiver. (SAH)|

Lascours, Jean; Albe, Virginie

2001-01-01

420

Optical clearing of archive-compatible paraffin embedded tissue for multiphoton microscopy  

PubMed Central

Standard histopathology techniques (including paraffin embedding) are incompatible with thick tissue multiphoton imaging, and standard clearing techniques on those specimens destroy some molecular information. We demonstrate multiphoton imaging in specimens prepared according to standard histopathology techniques. This permits unlabeled 3-dimensional histology on archival tissue banks, which is of great value in evaluating prognostic indicators.

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

2012-01-01

421

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

422

High (1 GHz) repetition rate compact femtosecond laser: A powerful multiphoton tool for nanomedicine and nanobiotechnology  

Microsoft Academic Search

Multiphoton tomography of human skin and nanosurgery of human chromosomes have been performed with a 1 GHz repetition rate laser by the use of the commercially available femtosecond multiphoton laser tomograph DermaInspect as well as a compact galvoscanning microscope. We performed the autofluorescence tomography up to 100 mum in the depth of human skin. Submicron cutting lines and hole drillings

A. Ehlers; I. Riemann; S. Martin; R. Le Harzic; A. Bartels; C. Janke; K. K鰊ig

2007-01-01

423

Resonance enhanced multiphoton ionization spectra of molecules and molecular fragments. Annual technical report, March 1991--February 1992  

SciTech Connect

Resonance Enhanced Multiphoton Ionization (REMPI) utilizes pulsed laser radiation to prepare a molecule in an excited state via absorption of one or more photons and to subsequently ionize that state before it can decay. The overall objective of this effort is to carry out theoretical studies of these REMPI processes in molecules and molecular fragments which are designed to provide a robust analysis and prediction of key spectral features of interest in several experimental studies and applications of this technique. A specific and very important objective of the effort is to predict the vibrational and rotational ion distributions which result from REMPI of representative molecules and to understand the underlying mechanisms that give use to these ion distributions. The author highlights progress made during this period.

NONE

1993-12-31

424

Excited-state intramolecular proton transfer reaction modulated by low-frequency vibrations: An effect of an electron-donating substituent on the dually fluorescent bis-benzoxazole  

Microsoft Academic Search

Excited-state intramolecular proton transfer (ESIPT) reaction has been studied in a molecule showing dual fluorescence, the 2,5-bis(2-benzoxazolyl)-4-methoxyphenol (BBMP), and its isotopomers, where the methoxy, and alternatively, the OH group has been deuterated. Attention is focused on the influence of electron donating OCH3 substituent on fast excited state reaction. Comparison between the resonance-enhanced multiphoton ionization spectrum and the laser-induced excitation of

J. Sepiol; A. Grabowska; P. Borowicz; M. Kijak; M. Broquier; Ch. Jouvet; C. Dedonder-Lardeux; A. Zehnacker-Rentien

2011-01-01

425

Low cost laser system generating 26-fs pulse duration, 30-kW peak power, and tunability from 800 to 1200 nm for multiphoton microscopy  

NASA Astrophysics Data System (ADS)

We demonstrate a novel low-cost, low-noise, tunable, high-peak-power, ultrafast laser system based on a SESAMmodelocked, solid-state Yb tungstate laser plus spectral broadening via a microstructured fiber followed by pulse compression. The spectral selection, tuning, and pulse compression are performed with a simple prism compressor. The spectral broadening and fiber parameters are chosen to insure low-noise and short pulse operation of the tunable output. The long-term stable output pulses are tunable from 800 to 1200 nm, with a peak power up to 30 kW and pulse duration down to 26 fs. We demonstrate the generation of an output beam with 30 fs pulsewidth and multiple colors in infrared. In particular, we compressed selected spectral slices centered at 960 and 1100 nm suitable for imaging with green fluorescent protein and red dyes. Such a multicolor, 30 fs laser is ideally suited for simultaneous multispectral multiphoton imaging. This system is attractive for variety of applications including multiphoton (TPE, SHG, THG, CARS) and multimodal microscopy, nanosurgery, and optical coherence tomography (OCT). Such system is simpler, lower-cost, and much easier to use (fully turn-key) compared to a currently available solutions for near-infrared ultrashort pulses, typically a Ti:sapphire laser-pumped OPO.

Resan, Bojan; Brunner, Felix; Rohrbacher, Andreas; Ammann, Hubert; Weingarten, Kurt J.

2012-02-01

426

Single-photon counting multicolor multiphoton fluorescence microscope.  

PubMed

We present a multicolor multiphoton fluorescence microscope with single-photon counting sensitivity. The system integrates a standard multiphoton fluorescence microscope, an optical grating spectrograph operating in the UV-Vis wavelength region, and a 16-anode photomultiplier tube (PMT). The major technical innovation is in the development of a multichannel photon counting card (mC-PhCC) for direct signal collection from multi-anode PMTs. The electronic design of the mC-PhCC employs a high-throughput, fully-parallel, single-photon counting scheme along with a high-speed electrical or fiber-optical link interface to the data acquisition computer. There is no electronic crosstalk among the detection channels of the mC-PhCC. The collected signal remains linear up to an incident photon rate of 10(8) counts per second. The high-speed data interface offers ample bandwidth for real-time readout: 2 MByte lambda-stacks composed of 16 spectral channels, 256 x 256 pixel image with 12-bit dynamic range can be transferred at 30 frames per second. The modular design of the mC-PhCC can be readily extended to accommodate PMTs of more anodes. Data acquisition from a 64-anode PMT has been verified. As a demonstration of system performance, spectrally resolved images of fluorescent latex spheres and ex-vivo human skin are reported. The multicolor multiphoton microscope is suitable for highly sensitive, real-time, spectrally-resolved three-dimensional imaging in biomedical applications. PMID:15711876

Buehler, Christof; Kim, Ki H; Greuter, Urs; Schlumpf, Nick; So, Peter T C

2005-01-01

427

Green frequency upconversion fluorescence of symmetrical 1,3,4-oxadiazole derivative by femtosecond three-photon excitation  

NASA Astrophysics Data System (ADS)

Multiphoton-absorption properties of ? -conjugated symmetrical A - ? - D - ? - A chromophore, 3,6-Bis[2-{4-[5-(4-tert-butyl-phenyl)-[1,3,4]oxadiazol-2-yl]-phenyl}-vinyl]-N-ethylcarbazolyl, has been experimentally studied by using femtosecond laser pulse. At the wavelengths from 1205nm to 1570nm, the molecule shows large three-photon absorption (3PA) properties. The 3PA cross section reaches 4.5 * 10-24cm6.GW-2 at 1255nm. The output/input characteristic curve measured by nonlinear transmission method demonstrated a good optical power limiting performance based on 3PA mechanism. Luminous blue-green (about 477nm) up-conversion fluorescence excited by infrared laser pulse from 1205nm to 1570nm was easily observed in the quartz cuvette along the laser propagation direction. The material was also theoretically studied using Gaussian 03' software. The geometry, electronic structure, ground state charge distribution and excited state charge distribution were systematically calculated by HF/6-31G(d) and CIS/6-31G(d) method. Calculation results show that the obvious three-photon absorption and frequency up conversion fluorescence of this chromophore is attributed to its rigidity of chemical structu