bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotope Effect in the Vibrational Predissociation of van der Waals Molecules: Complexes of Glyoxal With H2 and D2
Authors: Beswick J. A. , Halberstadt N. , Jouvet C. , Soep B.
Published: March 2007

In this work photodissociation studies of glyoxal‐H2 (D2) molecules have been conducted in order to analyze the effect of the mass in the vibrational predissociation of van der Waals
complexes. The glyoxal‐H2 (D2) molecules have been formed in a supersonic expansion and
photodissociated by means of a tunable dye laser. The final state of the glyoxal fragments
has been determined by the analysis of the fluorescence spectrum. A significant isotope effect
on the branching ratios for predissociation has been found. An interpretation in terms of a
distorted wave diabatic treatment is presented.
Photoionization Dynamics of Small Molecules With SynchrotronRadiation: State Preparation by Pepico and Tpepico
Authors: Guyon Paul Marie
Published: March 2007

The use of synchroton radiation combined with TPEPICO experiments to study the photoionization
dynamics of molecules at Orsay′s synchroton radiation facility is discussed. The initial state preparation by
Threshold Photoelectron Spectroscopy and final state‐mass and internal energy spectroscopy by time of
flight analysis of photoelectrons as well as ions in coincidence with threshold electrons is illustrated by the
TPES of HCl, the TOF TPES of O2 and the TPEPICO spectra of NO+ fragments from the decay of state
selected N2O+ ions.
Soft X‐Rays Induced Fragmentation of Core Excited PolyatomicMolecules
Authors: Hubin-Franskin M.-J. , Furlan M. , Delwiche J. , Aouni H.
Published: March 2007

Recent progress made in the soft X‐ray induced fragmentation of polyatomic molecules has been briefly
reviewed. The Coulomb explosion model has been shown to be less valid as the size of the molecule
increases.
Photodissociation and Large Internuclear Distance Dynamics
Authors: Glass-Maujean M. , Beswick J. A. , Frohlich H.
Published: March 2007

The determination of the state of the excited photofragments gives informations on couplings occurring at
large internuclear distance. The H(1s) + H(n = 2) photodissociation of H2 is well explained with a
transition probability between the B and B′ continua occurring at r ≈ 15a0. The H(1s) + H(n = 3)
photodissociation of H2 presents unsolved questions.
Reactive Collisional Spectroscopy: Scalar and Vector InformationFrom Numerically Intensive Computing
Authors: Laganà Antonio , Gervasi Osvaldo , Alvariño José M.
Published: March 2007

Advances in computer technologies have made it possible to extend the numerical investigation of the
detailed structure of reactive properties to several atom–diatom systems. This has allowed a better
understanding of the energy structure of the reaction intermediate and of the role it plays when reaction
occurs.
High Resolution Laser Techniques Applied to Reaction Dynamics
Authors: Vetter Raymond J.
Published: March 2007

The applications of high resolution laser techniques to crossed‐beam experiments which are examined in
this paper concern: (a) the reactivity of atomic/molecular excited states and the influence of light
polarization and (b) the measurement of absolute and differential cross sections by use of the laserinduced
fluorescence technique performed in a coherent saturation regime.

Examples are provided by the crossed‐beam study of the Cs(7P) + H2 → CsH + H photochemical
reaction, where two C.W. single‐mode tunable lasers are used to excite Cs atoms and to probe CsH
product molecules. It is shown how the fine and hyperfine structures of the Cs atom are involved in the
reaction mechanism (harpooning). The measurement of the total cross section (≈4.10−16cm2) gives an
indication of the overall efficiency of the reactive process (Cs atoms in the 7P state) with respect to the
quenching ones (Cs atoms in 6S, 6P, 5D and 7S states). Finally, the differential cross section shows a
marked forward “peaking” of CsH products which narrows with collision energy but which is rather
independent of the product rotation.
Subthreshold Ionization of Weakly Bound Complexes: StochasticAnalysis of the Role of the Rydberg Quasicontinuum
Authors: Akulin V. M. , Aquilanti V. , Brunetti B. , Vecchiocattivi F.
Published: March 2007

Recent evidence for subthreshold ionization (i.e. electron loss at energies less than anticipated from
vertical transitions assuming adiabatic separation of nuclear motion) points at the role of nonadiabatic
coupling of high Rydberg terms of molecules. Sinai′s billiard model for the chaotic motion of the Rydberg
electron, that leads to a diffusion over the energy ladder as a result of electronic–vibrational exchange, is
suggested as the classical mechanism of autoionization. A quantum expression for the branching ratio
between autoionization and spontaneous fluorescence is obtained and discussed with reference to
experimental results on associative ionization in atomic collisions and on laser ionization of van der Waals
diatomics.
Reaction Path Description and Internal‐Mode Dynamics of MolecularRearrangement in HO2
Authors: Zuhrt Ch. , Zülicke L. , Schneider F. , Chapuisat X.
Published: March 2007

After brief general remarks and definitions for the reaction path concept in view of formulating physically
transparent and computationally feasible theoretical models, the HO2 system is studied for both the
bimolecular exchange reaction and the intramolecular H transfer (isomerization). The analysis includes
potential energy surface topography, reaction profiles and internal‐mode dynamics.
Production and Reactivity of Ionized Clusters in the Gas Phase
Authors: Giardini-Guidoni Anna , Mele Aldo
Published: March 2007

A brief review of the experimental methods to obtain gas phase cluster ions is reported. Supersonic
expansion and ionization, high pressure ion production and clusterization, ablation from solids are
techniques used to study cluster chemistry. Studies of cluster ion formation from metal, metal oxides and
metal carbides are illustrated together with considerations on their structure and stability.
Selective Photodissociation of Condensed and Adsorbed SmallMolecules by Specific Core‐to‐Bound Excitations: Evidence forUltrafast Dissociation Channels
Authors: Menzel Dietrich
Published: March 2007

The modification of photodissociation mechanisms of small molecules by adsorption on a solid or by
condensation is briefly reviewed. The coupling to the surroundings leads to quenching of easily
delocalizable primary excitations so that only strongly localized channels show up in dissociation (detected
by photodesorption, i.e. by the appearance of fragments in the gas phase). In reverse, fast direct
dissociation channels will be less in need of such localization and will be preferred over slow channels.
Investigation of dissociation induced by core excitations or core shake‐ups introduces an internal time
mark—core life time—to which reaction time can be compared. The example of small molecules, such as
CO or NO, adsorbed on transition metal surfaces is surveyed, in which complex multiple excitations
predominate in dissociation. Recent results on the core‐induced dissociation of condensed hydrogenic
molecules such as water, ammonia, and benzene have shown the existence of preferential dissociation
channels in the core‐to‐bound region. It is argued that these dissociation processes are at least competitive
with core decay; they are termed ultrafast. It appears that they should also exist in the free
molecules.
Rotational Analysis of the Rydberg Spectrum of Water
Authors: Child M. S. , Gilbert R. D. , Jungen Ch.
Published: March 2007

Two techniques for rotational analysis of the nd←1b1 Rydberg spectra of H2O and D2O are discussed—a
Coriolis coupled asymmetric top model for the room temperature 3d←1b1 cluster, and an extension of
multichannel quantum defect theory to asymmetric tops, which is applied to recent jet cooled photoionization
spectra of the nd←1b1 series converging to the (100) vibrational levels of H2O+ and D2O+. The
quantum defects obtained by the two methods are in good agreement and new ionization limits to the
(100) series are derived: IP(100) = 104985(2) cm−1 for H2O and 104262(1) cm−1 for D2O.
Dynamics of Fragmentation Reactions From Peak Shapes inMultiparticle Coincidence Experiments
Authors: Eland J. H. D.
Published: March 2007

An experimental survey of peak shapes in two‐parameter mass spectra from charge separation of doubly
charged ions has been combined with Monte‐Carlo simulations of peak shapes for different mechanisms.
As a result, the major mechanisms, deferred charged separation, secondary dissociation and concerted
explosion, can now be recognised. Finer details and a number of recurrent peculiar peak shapes remain
unexplained.
Stereodynamical Studies of Velocity Aligned Photofragments
Authors: Brouard M. , Duxon S. P. , Enriquez P. A. , Sayos R. , Simons J. P.
Published: March 2007

The state resolved stereodynamics of bimolecular reactions can be probed using velocity aligned
photofragments as reagents, and polarised, Doppler resolved laser detection techniques for the products.
The new strategy and its application to the reaction O(1D) + N2O→ NO + NO are outlined.
Dynamics of Quantum Selected Levels of Electronic Excited States ofSmall Molecules
Authors: Martínez E. , López M. R. , Basterrechea F. , Puyuelo P.
Published: March 2007

Dynamics studies of the electronic excited states of some small molecules have been carried out. Collision
free lifetimes of different rotational and vibrational levels of the A and B states of 130Te2 and 80Se2 have
been obtained. Predissociation studies of the B states of the Br2 and Cl2 molecules have been carried out.
Results are discussed in terms of perturbation or predissociation effects.
Theoretical Characterization of Transition State DynamicalResonances in Heavy–Light–Heavy Reactions
Authors: Aguilar A. , Albertí M. , Blasco R. , Gilibert M. , Giménez X. , González M. , Lucas J. M. , Prieto M. , Sayós R. , Solé A.
Published: March 2007

The resonant reactivity of three elementary Heavy–Light–Heavy reactions is presented and discussed.
Collinear reactivity, in which a vibrational adiabatic model is constructed, is used for a detailed analysis of
resonance phenomena, which appear as a direct consequence of transition state metastable states in the
strong interaction region of the potential energy surface. Their influence on the detailed mechanism of the
elementary process is also discussed. The shape of the resonant peak, and the phase and the Argand plot
of the S‐matrix are used for a further characterization.

Three‐dimensional approximate calculations are used to test the evolution of the energy dependent
structure present in detailed quantities when sums and integrations over all partial waves contributing to
reaction are taken into account to obtain the usual averaged global quantities such as integral state‐to‐state
cross sections.
Slow Relaxation Processes in SF6 Gas After Pumping by a CO2 Laser Pulse
Authors: Kitazima Iwao , Iwasawa Hiroshi
Published: March 2007

The vibrational energy relaxation and distribution in SF6 at the collisional condition of 2 Torr was
measured with the pump‐probe method by use of two tunable CO2 300 ns‐pulse lasers at the delay time up
to 400 μs. The 10.6 μs P(30) pump intensity was 0.4 J/cm2. The probed spectra, divided into two parts, the
induced transmission at the P(10)–P(22) and the absorption at the P(24)–P(32), were red‐shifted by 50 μs
and then slowly back to the initial. The time variation of induced signals was divided into the four regions
due to the following processes; (I) the formation of nonthermal distribution in the ν3 mode and
quasi‐continuum with 1 μs, (II) the broad redistribution by the rise‐up of vibrational temperature in
50 μs‐duration, (III) the molecular diffusion or expansion out of the pumped region locally heated up by
the V–T relaxation in another 60 μs, (IV) the gas cooling corresponding to the energy relaxation or
population depletion over 400 μs. So, this pump‐probe method at the collisional conditions will easily give us some informations, with a short gas cell and a suitable time scale, on those slow processes.
Characterization of New Excimer Pumped UV Laser Dyes I. p‐Terphenyls
Authors: Schneider D. J. , Landis D. A. , Fleitz P. A. , Seliskar C. J. , Kauffman J. M. , Steppel R. N.
Published: March 2007

The performance characteristics of a series of new excimer pumped ultraviolet dyes are presented.
Chemical structure modifications which influence dye performance are discussed. An evaluation of
several alternative solvents shows that p‐dioxane remains the solvent of choice based on dye performance.
The influence of the cover gas in the dye circulator was examined and results are presented to show how
dye performance can greatly depend on this factor.
Excimer Pumped Dye Mixtures for the Wavelength Region 340–380 nm
Authors: Landis D. A. , Schneider D. J. , Seliskar C. J.
Published: March 2007

Two binary mixtures of ultraviolet laser dyes in p‐dioxane solution are described. The tuning curve of each
mixture spans more than 30 nm of useful tuning range in the 340–380 nm wavelength region. Both
mixtures are robust with half‐lives comparable to, or in excess of, associated single dye values. These
mixtures degrade symmetrically with dye laser operation, making them useful throughout the entire life of
the mixture. A simple model for the mixture lasing, based on independent fluorescences of the component
dyes, is able to semi‐quantitatively match the tuning curves of the dye mixtures. The results presented
should be easily extendable to other dye mixtures.
Characterization of New Excimer Pumped UV Laser Dyes 2. p‐Quaterphenyls
Authors: Fleitz P. A. , Seliskar C. J. , Steppel R. N. , Kauffman J. M. , Kelly C. J. , Ghiorghis A.
Published: March 2007

New excimer‐pumped laser dyes based on p‐quaterphenyl are described and the associated performance
parameters are presented. A discussion of the variations in the performance parameters found is made in
terms of dye chemical structures. Most of the dyes studied are significantly better than the chosen
reference dye BBQ. The best dye in the series (dye 3) is stabilized both by ring‐alkylation and by ringbridging.
The net effect is the production of a new dye with a lifetime ten times greater than that of the
reference dye BBQ.
The Role of 6p States of Xe in the Discharge Pumped XeCl Laser Emission
Authors: Castillejo M. , Figuera J. M. , García-Moreno I. , Medina J. J.
Published: March 2007

The role played by 6p metastable Xe level in the kinetics of discharge pumped XeCl laser emission is investigated by performing time resolved and time integrated fluorescence studies of the Xe 6p–6s emissions produced in the discharge plasma at various pressures of chlorine donor compounds. The results analyzed according to a simple kinetic model suggest that 6p level is populated through a cascading mechanism involving various Xe levels which is enhanced by the presence of the halogen donor compound. The laser emission dependence is also investigated as a function of the halogen donor pressure. The observations lead to the conclusion that 6p states do not play a relevant role in the formation of XeCl* molecules and that other Xe excited states should be considered to account for the participation of the neutral channel in the XeCl* formation mechanism.
The Spectral Features of Polyatomic Molecules Multiphoton Excitation in a Strong IR‐Laser Field
Authors: Alimpiev S. S. , Sartakov B. G.
Published: March 2007

The experimental data on multiphoton excitation of polyatomic molecules in strong fields of high pressure continuously tunable CO2 lasers are presented. The program package for computer simulation of multiphoton excitation spectra and excitation dynamics is developed. Good agreement between computer simulation and experimental data is observed.
Selective Dissociation of C4F9 COI Molecules by the Second‐Harmonic Radiation of Pulsed TEA CO2 Laser
Authors: Bildinov I. K. , Laptev V. B. , Ryabov E. A. , Tumanova L. M.
Published: March 2007

IR multiphoton dissociation of C4F9 COI was studied by the second‐harmonic radiation of TEA CO2 laser. The stretching vibration of the carbonyl bond νC = O was excited. The second harmonic of CO2 laser was generated with the use of nonlinear crystal AgGaSe2. The maximum energy fluence at focus was Φ ≃ 1.2 J/cm2. The MPD of C4F9 COI was proved to be effective and selective with respect to oxygen and carbon isotopes. The main dissociation products were C4F9I and CO. The dissociation product, CO, was enriched with both 16O and 12C when the C4F9 COI molecule was excited at the center of the band νC = O by the laser line 10P (18) with 2ωlas = 1797.2 cm−1. The maximum selectivities measured for oxygen and carbon were α(16/18) = 20 and α(12/13) = 25 respectively.
UV Laser Induced Chemistry of Adsorbed Dimethylcadmium
Authors: Varakin V. N. , Simonov A. P.
Published: March 2007

The UV laser chemistry of dimethylcadmium (DMCd) either chemisorbed at 297 K on n‐type Si(100) with native oxide or physisorbed at 150 K on a photodeposited cadmium film has been studied by using mass spectrometry of desorbed species. A XeCl laser induced the heterogeneous fragmentation of these chemisorbed molecules as well as the desorption of DMCd, Cd, and CH3. The resonant absorption of a KrCl laser radiation by adsorbed DMCd led to their photolysis and the ejection of DMCd and its fragments in both neutral and ionic forms. The kinetic, laser fluence, and time‐of‐flight dependences of desorbed species have been measured to elucidate the mechanisms of the dissociative and desorption processes either induced by lasers or occurring spontaneously. The effects of these lasers on chemisorbed DMCd as well as KrCl laser assisted processes in chemisorbed and physisorbed molecules have been compared.
Accurate Wavenumber Measurement in High Resolution Stimulated Raman Spectroscopy (SRS) by Using an Infrared Standard. ν1 Fundamental of 12CH4
Authors: Santos J. , Cancio P. , Domenech J. L. , Rodriguez J. , Bermejo D.
Published: March 2007

A new set of wavenumbers for the Stimulated Raman Spectrum (SRS) of the ν1 band of 12CH4 is presented using the Infrared (IR) absorption spectrum of the P10 component of ν3 of the same molecule as a wavenumbers standard. An estimation of the Stark shift due to the pump laser field is experimentally deduced what allows to extrapolate the measured wavenumbers to zero field amplitude. A careful discussion about the main possible error sources and how to cope with them is also included.

The absolute accuracy of the wavenumbers set presented here is believed to be at least one order of magnitude better as compared with previous measurement.
Theoretical Methods for the Analysis of Spectra of Highly Vibrationally Excited Polyatomic Molecules
Authors: Borondo F. , Llorente J. M. Gomez , Benito R. M.
Published: March 2007

The vibrational spectra of classically chaotic systems are usually very complicated and seemingly unassignable. In this paper, two methods for the analysis of spectra of highly vibrationally excited polyatomic molecules are described, and some results for the floppy molecules HCN and LiNC are presented. By application of these methods, relevant information on the underlying dynamics is obtained, thus establishing a bridge between the spectroscopy and the dynamics of these systems.
Consecutive Vibrational Redistribution and Predissociation Processes in s‐Tetrazine–Argon Van Der Waals Complexes
Authors: Ramaekers J. J. F. , Krijnen L. B. , Lips H. J. , Langelaar J. , Rettschnick R. P. H.
Published: March 2007

s‐Tetrazine argon complexes T − Arn (n = 1, 2) are formed in a supersonic expansion
of argon seeded with s‐tetrazine. The expansion was conducted through a nozzle of
50 or 100 μm with an argon stagnation pressure between 1 and 1.5 bar. From spectrally
resolved measurements it is clear that vibrational redistribution processes as well as
vibrational predissociation processes take place after SVL excitation within the
complex.

From rise and decay time experiments it can be concluded, that after excitation of
the 6a1 complex level, the above mentioned processes are consecutive and not parallel.
It appears that the out of plane mode 16a couples with the Van der Waals stretching
mode. The predissociation rate of the 16a2 complex is observed to be 2.3 × 109 s−1.
Very Low Energy Collision Induced Vibrational Relaxation: An Overview
Authors: Rice Stuart A. , Cerjan Charles
Published: March 2007

Recent experimental and theoretical studies of very low energy collision induced
vibrational relaxation in diatomic and polyatomic molecules are surveyed. Emphasis
is placed on the novel features of the very low energy process; these require a full
quantum mechanical treatment of the collision to account for the observations.
Laser Studies of Metal Cluster Beams
Authors: Smalley R. E.
Published: March 2007

Recent developments in laser and molecular beam technology have now made it
possible to produce supersonic beams of virtually any element in the periodic table.
Using laser vaporization of the appropriate target, the beam source conditions may
be adjusted to produce either the cold free atoms alone, or clusters of these atoms
with each other—or with another element. Since the vaporization laser heats only a
small spot on the target, extremely high local temperatures can be obtained without
heating any other part of the apparatus; and beams of even the highest boiling element
(tungsten) are readily obtained both in atomic and cluster form. The physics and
chemistry of these exotic cluster species is almost completely unknown on the fundamental
level. Even for clusters containing 100 atoms, most of these atoms lie on the
surface, and the chemical and physical properties will be predominately surface
phenomena. Initial studies of these clusters have entailed the use of one‐ and two‐ photon
laser ionization with time‐of‐flight mass selective detection. Using a variety of
fixed frequency lasers, the work function of copper clusters has been examined as a
function of cluster size in the range from 2 to 29 atoms per cluster. Considerable
detailed information has also been obtained for the electronic structure and bond
lengths of a number of transition metal dimers and trimers (including Cu2, Cr2, V2,
Mo2, and Cu3) through the use of high resolution laser spectroscopy with mass‐selective
photoionization detection.
Molecular Beam Studies of Primary Photochemical Processes
Authors: Lee Yuan T.
Published: March 2007

Application of the method of molecular beam photofragmentation translational spectroscopy
to the investigation of primary photochemical processes of polyatomic
molecules is described.

Examples will be given to illustrate how information concerning the energetics,
dynamics and mechanism of dissociation processes can be obtained from the precise
measurements of angular and velocity distributions of products in an experiment in
which a well defined beam of molecules is crossed with a laser.
Intramolecular Vibrational Relaxation in Electronically Excited States
Authors: Voltz R. , Boeglin A. , Villaeys A. A. , Lin S. H.
Published: March 2007

A density matrix approach for describing intramolecular dynamics, with special application
to vibrational relaxation in excited electronic states, is presented. We derive the
master equations governing intramolecular transfer of excitation energy between the
states in a zeroth‐order basis defined by considering the excitation and detection
conditions in the time‐resolved experiments. It is shown that, in this formalism, the
memory function plays a central role. We note that the form of intramolecular memory
is determined by the importance of quantum mechanical mixing of the zeroth‐order
states. A distinction is made between the subsystems of states with strong and weak
mixing properties; while the former account for quasiperiodic character of coherent
motion, the latter display a Markovian behavior. The physical conditions fixing the
relative importance of quasiperiodic and statistical dynamics in individual systems are
discussed. In the application to time resolved intramolecular vibrational relaxation,
special consideration is given to the nature of the initially excited doorway states and
the intermode couplings. The symmetry restrictions and the possible role of rotational
motion in vibrational relaxation are also discussed, before considering the recent results
obtained by Zewail et al. with anthracene in the first excited singlet state.
Intramolecular Vibrational Redistribution at Low State Densities in S1 Aromatics. Evidence for Rotational Contributions
Authors: Dolson D. A. , Holtzclaw K. W. , Lee S. H. , Munchak S. , Parmenter C. S. , Stone B. M. , Knight A. E. W.
Published: March 2007

Evidence is presented concerning the onset of intramolecular vibrational redistribution
(IVR) as one climbs the vibrational manifold of room temperature S1 aromatics. The
onsets of IVR occur at S1 vibrational energies between 670 and 2000 cm−1 for various
single and double ring aromatic molecules. The vibrational level densities in the onset
region seem too small to support the extensive IVR that is observed in every molecule.
Comparisons of room temperature fluorescence spectra with cold supersonic beam
spectra from p‐difluorobenzene support the proposition that Coriolis vibration–rotation
coupling makes important contributions to the effective density of states in room
temperature IVR.
Ionic State Relaxation Processes in VUV‐Excited Polyatomic Molecules
Authors: Leach Sydney , Dujardin Gérald
Published: March 2007

Advantages of molecular ions for the study of electronic radiationless transitions are
discussed. Several coincidence techniques for measuring key relaxation parameters are
briefly described. The different cases of radiationless transition studies of molecular
ions are outlined and examples mentioned. Coincidence measurements between threshold
photoelectrons and ion fluorescence photons emitted by VUV‐excited
hexafluorobenzene are presented. The radiative, kr, and nonradiative, knr, relaxation rates for specific vibrational levels in the and states of are derived from the measured lifetimes and quantum yields of ion fluorescence. The kr rate for excitation of the , 0° level is found to be about 25% of that for the state where kr = (18±3) × 106 s−1. The knr rates for the 1n and 1n21 progressions in the state increase with n but exhibit a mode selective behavior. Model calculations of knr confirm the mode selectivity.
These calculations were carried out on a noncommunicating, harmonic oscillator basis.
Progressive deviations between experimental and calculated results are interpreted as indicating the
gradual onset of vibrational redistribution with increasing vibrational energy.
The results illustrate a new method for demonstrating the growing in of intramolecular vibrational relaxation.
Photon Echoes Made Simple
Authors: Beach R. , Brody B. , Hartmann S. R.
Published: March 2007

Photon Echoes in gases are analyzed via the Billiard Ball Echo Model both in the
short and long pulse limit where the “atoms” are represented as spherical and elliptical
billiard balls, respectively. Recent experiments demonstrating the elliptical billiard ball
shape are presented using intensity data which ranges over close to eleven orders of
magnitude.
Applications of the Local Mode Model to CH Bond Length Changes, Molecular Conformations and Vibrational Dynamics
Authors: Henry Bryan R. , Gough Kathleen M.
Published: March 2007

The theoretical basis for the local mode model is reviewed. The model is applied to
gas phase overtone spectra of aromatic molecules to investigate both substituent
induced CH bond length changes and conformationally inequivalent hydrogens. The
dynamic implications of the local mode model are discussed.
Preliminary Investigations About the Cs*+H2 Collision
Authors: Gadea X. F. , Jeung G. H. , Pelissier M. , Malrieu J. P. , Picque J. L. , Rahmat G. , Verges J. , Vetter R.
Published: March 2007

The possible photoreactions leading to the formation of “laser snow” in cell experiment
by laser irradiation of Cesium atoms to the (7p) level will be analyzed through crossed
beam experiment. A single collision process would be excluded if an activation barrier
was present in the inverse ground state reaction CsH + H → Cs + H2; accurate ab initio
calculations exclude the existence of such a barrier. The ionic state Cs+ + is suggested to make possible the electronic into vibrational energy transfer in the
perpendicular collision.
Determination of Vibrational Energy Distributions of CN (A  2Πi) and (X  2Σ+) from the C+N2O Reaction by Chemiluminescence and Laser Induced Fluorescence
Authors: Dorthe G. , Joussot–Dubien J. , Nouchi G. , Kottis Ph.
Published: March 2007

The CN (A  2Πi) and (X  2Σ+) vibrational distributions from the C + N2O → CN + NO reaction at 300 K were determined in a low pressure flow reactor. From the chemiluminescence
A  2Πi→X  2Σ+ the vibrational distribution of A  2Πi was found to peak at υ′ = 1. From the laser induced fluorescence
B  2Σ+→X  2Σ+, the vibrational distribution of X  2Σ+ was found to peak at υ″ = 4.

A C2H2—N2O combustion flame, stabilized at 2.8 torr with a temperature of 2500 K,
gave a CN (A  2Πi) vibrational distribution peaking at υ′ = 2 which can be attributed to the C+N2O
reaction at 2500 K. However the CN ground state vibrational distribution was found to be relaxed.
The Spectrum of the Molecular Eigenstates of Pyrazine and the Reconstruction of Decays of Rotational States of the  1B3u (0–0) Transition of Pyrazine
Authors: van der Meer Barend J. , Jonkman Harry Th. , Kommandeur Jan
Published: March 2007

The spectrum of the molecular eigenstates (ME) belonging to the various rotational
members of the  1B3u (0–0) transition of pyrazine was measured with a very narrow
band laser in a molecular beam with a Doppler width of 30 MHz.

It is shown that, when the ME′s belonging to a single rotational state are Fourier‐transformed,
the beating decays of these states are obtained. A problem is constituted
by the lack of a fast component in these reconstructions, while it is observed in
experiments on higher J‐states.
1B3u Pyrazine. Experimental Tests of the Theory of Radiationless Transitions
Authors: Matsumoto Y. , Spangler L. H. , Pratt D. W.
Published: March 2007

Pyrazine (1,4‐diazabenzene) has played a central role in the development of the theory
of radiationless transitions. In this paper, we will describe studies of the decay behavior
and fluorescence quantum yield of the isolated molecule and several of its isotopically
labelled derivatives following pulsed dye laser excitation of “single” rotational levels
of the  1B3u (nπ*) state in a seeded supersonic jet, both in the presence and absence
of an external magnetic field. We shall demonstrate that pyrazine can be transformed
from a “small” molecule to a “large” molecule by very small perturbations; e.g., by
climbing up the rotational ladder of the first excited singlet state, by isotopic labeling,
and/or by applying dc magnetic fields of the order of 100 G. Thus, the experiments
provide important tests of the predictions of the theory for the first time. Specifically,
we will show that, under “intermediate‐case” conditions, (1) the fast component of
the decay is indeed coherent in nature, (2) the coupled state is triplet in character
(and, thus, that the process we are monitoring is intersystem crossing (ISC)), (3) nuclear
spin is conserved in ISC, (4) rotations and small magnetic fields play an important role
because of the angular momentum selection rules for ISC, and (5) the levels mixed
by the magnetic field are most likely the fine‐structure components of the different
angular momentum levels of the mixed, singlet–triplet state. The relationship of these
results to those of other workers in the field will also be discussed.
Advances in Femtosecond Optical Spectroscopy Techniques
Authors: Shank C. V.
Published: March 2007

This paper reviews the recent advances in optical pulse measurement techniques which
have made possible the investigation of ultrafast phenomena in condensed matter on
a time scale of 100 femtoseconds or less. Recent results in pulse generation,
amplification, white light continuum generation, and pulse compression will be discussed.
In addition, applications of these pulses for measurement will be discussed.
Chemical Reactions in Solution: The New Photochemistry
Authors: Robinson G. Wilse , Jalenak Wayne A.
Published: March 2007

Understanding the dynamics of chemical reactions in the condensed phase reaches a
new plateau with each technological advance in time‐resolved spectroscopy. Submicrosecond
studies of the past revealed the role of long range molecular diffusion in
condensed‐phase chemistry and photochemistry. The picosecond (10−12–10−9 s) time
scale, combined with the use of a high concentration of reactants, can provide new
information about the “microdynamics” in the local region of the reaction itself. The
role of solvent is particularly important: how it attaches to an activated reactant
molecule, how it is displaced by the other reactant molecule preparatory to reaction,
and how the solvent behavior affects the dynamics of single‐ and multi‐channel
processes, thus the relative yields of products in competing reactions. The theory
presented here divides itself into two types: one that depends on a diffusion equation
that also contains terms describing a distance‐dependent reaction sink function and a
reaction barrier; and a second type that deals phenomenologically with rate equations,
including the rate of reactant/solvent interchange. Experiments subdivide naturally
into steady state and transient measurements, the former dealing with quantum yields
and steady state spectroscopic studies, the latter with picosecond transient spectroscopy.
The two theoretical approaches can be interrelated in certain useful limits. The two
types of experimental data, in combination with the theory, supply fundamental
information about solvent participation in the local reaction region.
Picosecond Spectroscopy of Solutions, Proteins and Photosynthetic Membranes
Authors: Fleming Graham R. , Lotshaw William T. , Gulotty Robert J. , Chang Mary C. , Petrich Jacob W.
Published: March 2007

The photophysics of tryptophan is discussed and a model capable of rationalizing the
photophysics of almost twenty derivatives of tryptophan is proposed. The model is
based on conformers about the Cα—Cβ bond and the relative rates of charge transfer
from indole to various electrophiles. Three new tryptophan derivatives were synthesized
to test the model. Accurate predictions concerning the relative fluorescence lifetimes
and the form of the fluorescence decay law are made for tryptophan and seventeen
of its derivatives, including the three new derivatives.

The fluorescence decay kinetics from chloroplasts from green plants are described.
New data are presented on the fluorescence decays obtained from genetic mutants of
chlamydomonas which lack specific components of the photosynthetic apparatus. The
interpretation of the green plant chloroplast data in terms of the two photosystems
and the light harvesting array is discussed in terms of the data from the mutant algae.
Our data indicate that the major short component (∼100 ps) obtained in the fluorescence
decay of chloroplasts results from photochemical trapping by both photosystem
I and photosystem II.

A synchronously pumped dye laser which produces two, independently tunable,
synchronized picosecond pulse trains will be described. An application of the laser to
time and frequency resolved polarization spectroscopy will be given. The results are
used to estimate the homogeneous linewidth of the S0 → S1 transition of a large
molecule in solution. The optical heterodyne technique is applied to separate the real
and imagninary contributions of the third order nonlinear susceptibility.
Laser Ionization Studies of Gas Phase and Surface Adsorbed Molecules
Authors: Meek Jon T. , Long S. Randolph , Opsal Richard B. , Reilly James P.
Published: March 2007

Gas phase hydrocarbons are ionized using the output of UV excimer lasers and
frequency doubled dye lasers. The ions generated are mass resolved and kinetic energy
distributions of ejected photoelectrons are recorded. Information about the photochemistry
and ion spectroscopy of benzaldehyde, benzene and toluene is derived.
Molecules adsorbed to metal surfaces are also laser ionizable leading to distinctively
sharp peaks in their laser induced time of flight mass spectra.
Excitation‐Wavelength‐Dependent Structure in the Fluorescence Spectra of Bu States of Diphenylpolyenes
Authors: Boczar Bruce P. , Felder Thomas C. , Topp Michael R.
Published: March 2007

Experiments have used a tunable picosecond laser to study evolving fluorescence
spectra of 1,8‐diphenylocta‐l,3,5,7‐tetraene (DPO) in hexane solution at room temperture.
The spectra recorded synchronously (±20 ps) with the irradiation event are
analysed in terms of the time‐integrated spectra, spectra obtained through a delayed
gate, resonance Raman signals and fluorescence from the second excited singlet state.
Data are presented to show the dependence of the S2 →
S0 spectrum on the excitation wavelength.
The spectra clearly show that vibrational relaxation is incomplete on the
timescale of the S2 lifetime. On the other hand, the spectral bands show little tendency
at room temperature towards line‐narrowing effects. This indicates that the rate of
molecular site relaxation is at least comparable to the lifetime of the S2 state under
these conditions.
The Self‐Injected Laser for Picosecond Time‐Resolved Spectroscopy
Authors: Armani F. , de Martini F. , Mataloni P.
Published: March 2007

The principles of operation and the characteristics of the self‐injected picosecond laser
are presented. We show that in spite of its simple design our device is able to generate
very high power pulses in the picosecond domain. This warrants the use of this laser
for time resolved spectroscopy in the picosecond domain.
Picosecond‐Duration Vibrational Relaxation Kinetics in the Excited S1 State of Perylene and Anthracene Molecules
Authors: Freiberg A. , Tamm T. , Timpmann K.
Published: March 2007

We present and discuss the results of a direct observation of the picosecond range
temporal behavior of vibronic lines in the luminescence spectrum of the matrix‐isolated
perylene and anthracene molecules. A novel subtractive dispersion mount of monochromators
in conjunction with the synchroscan streak camera has been used. From
spectrochronograms measured at different excitation wavelengths the vibrational
energy relaxation times have been obtained. These are in the range of 20–30 ps and
are most probably determined by the existence of the phonon bath of the matrix. A
comparison of the measured relaxation constants with those estimated from the
steady‐state hot luminescence spectrum has been made.
New Developments in Laser Dyes
Authors: Schäfer F. P.
Published: March 2007

Recent achievements and potential for further developments in laser dyes are discussed
with emphasis on wavelength coverage, efficiency and photochemical stability. It is
shown that significant progress in efficiency and photostability can only be expected
from new laser dyes assembled in an unconventional way from molecular subunits.
Multiphoton Ionization Mass Spectrometric (MPIMS) Study of Phenol: Mechanism of Ionic Fragment Formation
Authors: Pandolfi R. S. , Gobeli D. A. , Lurie Jonathan , El-Sayed M. A.
Published: March 2007

Time of flight (TOF) mass spectrometry is used in conjunction with a variable repelling
voltage technique to elucidate the mechanism by which phenol ionizes and dissociates
under 266 nm pulsed laser irradiation in combination with a 532 nm or 355 nm pulsed
laser. The results suggest that, like benzene, the molecular ion is the predominant
precursor of all ionic species generated in the process. Predominance of species
at relatively low powers confirms the presence of a low energy dissociation channel
involving the elimination of CO. The use of a second laser at 532 nm is found to
selectively destroy the (as compared to the parent ion) species. The parent ion
is found to be protected from the radiation of the second laser pulse at 532 nm but
not at 355 nm if the second laser pulse is delayed by 50 ns. This is explained in terms
of relaxation within the parent ion energy levels, the location of a low energy dissociation
channel and the wavelengths of the lasers used. The main aspects of the fragmentation
pattern are discussed in terms of the statistical theory of Rebentrost and Ben‐Shaul.
Redox Properties of Cobalt Tetraphenyl Porphyrin Adsorbed on Semi‐Conductor Oxides Studied by Photoacoustic Spectroscopy
Authors: Merle A. M. , Brzezinski L. , Cherqaoui A. , Giannotti C.
Published: March 2007

Photoacoustic spectroscopy has allowed to show that physisorbed CoIITPP is ground
state monooxidized into (CoIIITPP)+ when adsorbed on Nb2O5, TiO2, SrTiO3, ZnO,
SnO2. A double oxidation is observed when the porphyrin is adsorbed on WO3. On
the contrary when it is adsorbed on ZrO2 and SiO2, oxidation only occurs if the
porphyrin has been driven by irradiation in its excited state. It remains in the reduced
form when adsorbed on Ta2O5. This behavior has been correlated with the band
positions of these various oxides and has allowed to roughly position the oxidation
potential of CoTPP in adsorbed state ∼0.8 V higher than in solution (0.5 V/SCE or
5.3 V/vacuum) that is 4.5 V/vacuum.
The Tunable, Narrow‐Bandwidth Excimer Laser, the New Workhorse for Photochemistry in the UV and VUV
Authors: Hohla K. , Mückenheim W. , Basting D.
Published: March 2007

Excimer lasers are powerful sources of radiation in the UV, providing several laser
lines between 157 and 353 nm. The excimer laser transition is bound‐free, and thus
the emitted wavelengths are broad‐band (up to 200 cm−1). In addition the high gain
(0.15 cm−1) of the laser gas causes a rather large divergence (>1 mrad) in conventional
excimer lasers.

A new excimer laser concept is described which improves the spectral brightness in
terms of watt/(rad × bandwidth) by three orders of magnitude. This allows, through
non‐linear processes such as Raman shifting the fundamental output and four‐wave‐mixing
in gases, the generation of new laser lines in the UV and VUV.
A Study of the Mutual Diffusion Coefficient in a Binary Liquid Mixture, Using a Laser Beating Technique
Authors: El-Mekawey F. M.
Published: March 2007

Line‐widths of light scattered by nitrobenzene‐heptane system are measured over a
wide temperature range including the vicinity of the critical temperature of separation.
The critical exponents are measured. Noncoincident value of the critical exponent for
the states of the system above and below the critical temperature of separation are
obtained.
Energy Partitioning in Molecular Photodissociation: Methyl Nitrite Photolysis
Authors: Lahmani F. , Lardeux C. , Solgadi D.
Published: March 2007

The photodissociation of methyl nitrite CH3ONO in three different electronically
excited states has been studied by determining the internal state distribution of one
of the photofragments. The fluorescence of NO A  2Σ+ produced for excitation of
CH3ONO between 1200 and 1650 Å and of CH3O 2 A1 produced at 1930 Å has been
investigated. The vibrational distribution in both species can be explained by statistical
considerations. The rotational excitation of NO A  2Σ+ is of Boltzmann type. For
CH3ONO excited in the first nπ* excited state at 3550 Å the NO X fragment has
been probed by a two photon laser excited fluorescence technique. The nascent
NO X υ″ = 0, 1, 2, 3 exhibit a population inversion and a high degree of rotational
excitation.
HF Fluorescence and Ion Production From Infrared Laser Irradiationof SF6‐Hydrocarbon Mixtures
Authors: Scypinski S. , Kaldor A. , Cox D. M.
Published: March 2007

CO2 laser irradiation of SF6/hydrocarbon mixtures are shown to produce positive ions
and infrared fluorescence due to emission by HF≠. The mechanism for the production
of these ions and fluorescence involves the multiple photon dissociation of SF6 and
subsequent attack of the free fluorine atom on the hydrocarbon, as well as V → V
transfer and thermal ionization reactions. Argon and oxygen are found to increase ion
production while quenching the fluorescence. Chemi‐ionization of the hydrocarbons
by a reaction sequence initiated by the attack of fluorine atoms on trace amounts of
an oxygen impurity cannot be disregarded as a channel for ion formation.
Picosecond Laser Study of Thioindigoid Dyes Photoisomerization
Authors: Krysanov S. A. , Alfimov M. V.
Published: March 2007

The transient species in the trans ⇌ cis photoisomerization of the perinaphto–thioindigoid
dye were identified by picosecond laser spectroscopy in the time domain
10 ps–5 ns. An excitation of the trans isomer with a 6 ps, 528 nm pulse to the singlet
state S1 (the peak of ← S1 absorption at 700 nm) results in the intersystem crossing
S1 ⇝ T1 (the peak of Tn ← T1 absorption at 730 nm) with the quantum yield of 0.7 and rate constant (1.4 ± 0.3)· 109s−1. An excitation of the cis isomer results also in
the intersystem crossing (the peak of Tn> ← T1 absorption at 670 nm) with the rate
constant (3.7 ± 1.2)· 1010s−1. The triplet mechanism of the photoisomerization in the
both directions is proposed.
Frequency Doubled CO2 Laser Induced Decomposition of CarbonylCompounds: Cyclobutanone
Authors: Au Mei-Kuen , Hackett P. A. , Humphries M. , John P.
Published: March 2007

This paper reports the first use of radiation derived from a TEA carbon dioxide laser
by nonlinear upshifting techniques (second harmonic generation) in initiating multiphoton
absorption and dissociation. The frequency doubled CO2 laser has frequency
coverage from 2180–1750 cm–1. This frequency region is of importance as it allows
pumping of the fundamental stretching modes of organic carbonyl groups (anhydrides,
acyl chlorides and strained cyclic ketones), inorganic carbonyl groups, and carbontritium
bonds. The laser has been used to excite cyclobutanone in the region of the
carbonyl stretch. Efficient multiphoton absorption and two channel dissociation are
observed. The product array is consistent with that observed upon excitation at 10 μm.
Two‐Quantum Photoprocesses in DNA and RNA Biopolymers UnderPowerful Picosecond Laser UV Irradiation
Authors: Nikogosyan David N. , Gurzadyan Gagik G.
Published: March 2007

Two‐quantum photoreactions taking place under picosecond laser UV irradiation of
DNA and RNA biopolymers were investigated. Despite of qualitative difference in
two‐step photoprocesses concerned (single‐strand breaks formation in plasmid pBR
322 DNA, induction of breaks in TMV RNA sugar‐phosphate chain, cross‐links
formation in DNA of CD phage) similar dependences of the quantum yield of the
effects studied on the irradiation intensity can be observed with saturation in the region
of 3 · 1011−3 · 1012 W/m2. The saturation intensity is one or two orders lower than in
the case of irradiation of single monomers ‐ nucleic acid bases.
Computer Simulations ofViscosity Dependent MolecularRelaxation Processes
Authors: Kaschke M. , Kleinschmidt J. , Wilhelmi B.
Published: March 2007

The dependence of excited‐state lifetime, fluorescence quantum yield and isomerization
rate of organic dye molecules on solvent viscosity has been a subject of numerous
experimental and theoretical investigations. To explain the viscosity dependence of
excited‐state lifetime in this paper the temporal behavior of the excited state population
is calculated for several models of the molecular relaxation process by a computer
simulation incorporating both the stochastical motion of large molecular parts in the
excited state and relaxation transitions. The described method is applicable to calculating
the probability of changing the electronic state as a function of time and internal
rotation coordinate.