bluuebunny/crossref_metadata_2025 huggingface dataset:
Capillar Gas ChromatographyWith Laser Optothermal Detection
Authors: Zharov V. P. , Montanari S. G.
Published: March 2007

The design of a through‐flow laser opto‐thermal (OT) detector intended for operation
as a selective chromatographic detector in combination with capillary columns is
described. The main advantage of such a detector is its relative simplicity and high
spatial resolution. A new differential scheme of OT detector which can reduce the
background signals of scattered radiation by about 102 times is suggested. The threshold
sensitivity of OT detector is experimentally estimated to be equal to about 7 ng (ethanol).
The higher selectivity of the developed system “gas capillary chromatograph + laser OT
spectrometer” has been demonstrated by analyzing a mixture of five atomatic hydrocarbons
with the use of a tunable CO2 laser. Recommendations for further modification
of the equipment are given.
Molecular Beam Opto‐thermalStudy of the Multiple‐photonInfrared Excitation of CF3Br
Authors: Bassi D. , Boschetti A. , Iannotta S. , Scotoni M. , Zen M.
Published: March 2007

The multiple‐photon excitation (MPE) of CF3Br has been studied in strictly collisionless
conditions by means of the molecular beam optothermal technique. The MPE spectrum
shows strong structures which have been attributed to different orders of multiple‐photon
resonances. The experimental results have been compared with an available theoretical
calculation based on the “heat‐bath feed‐back” model. The effect of the rotational
population and of the vibrationally excited “hot bands” on the MPE yield is discussed.
Simple Method for Obtaining Multiple‐FrequencyRadiation From a Single CO2 Laser
Authors: Evseev Alexander V. , Puretzky Alexander A.
Published: March 2007

A simple method to obtain from a single CO2
laser a multiple‐frequency radiation suitable for experiments
in laser chemistry is suggested and experimentally
realized.
Quantum Yield of ThirtyPicosecond OxyhemoglobinPhotodissociation. Effect ofProtein Fluctuations on theQuantum Yield Values
Authors: Valat P. , Alpert B.
Published: March 2007

We have measured the absolute quantum yield of the oxyhemoglobin photodissociation
with a 30 ps laser pulse excitation. We report that oxyhemoglobin dissociates with the
same yield as carboxymyoglobin under photostationary conditions. Based on the
picosecond and nanosecond experimental data, we show that oxygen geminate recombination
is responsible for the low quantum yield values of oxyhemoglobin photodissociation
measured with longer photolysis flashes. Kinetic data suggest that two geminate
regimes which successively appear in oxygen recombination can be resolved. The first
can be entirely attributed to the hemoglobin‐iron chemical reactivity and, the second
to the action of protein fluctuations.
Biostimulating Action ofLow‐Intensity MonochromaticVisible Light: Is it Possible?
Authors: Karu T. I. , Tiphlova O. A. , Fedoseyeva G. E. , Kalendo G. S. , Letokhov V. S. , Lobko V. V. , Lyapunova T. S. , Pomoshnikova N. A. , Meissel M. N.
Published: March 2007

The quantitative studies with organisms of different complexity (HeLa cells, yeast
organisms, E coli bacteria) to prove or disprove the stimulating action of low‐intensity
visible light are presented. The stimulation of DNA synthesis in HeLa cells was observed
for four spectral intervals with maxima at near 400, 620, 680 and 760 nm. The red light
stimulates the growth of yeast (Saccharomycodes ludwigii) and E coli in exponential
growth phase. The action spectrum of monochromatic light on the growth of these
organisms in the red region is very similar to that for HeLa cells.
Multiple Photon High VibrationalCH Overtone Resonant andOne‐Photon Dissociation ofToluene Radical Cation
Authors: Simonov A. P. , Abakumov G. A. , Yaroslavtzev V. T. , Lunchev V. A. , Fedorov E. A.
Published: March 2007

Photodissociation of molecular radical cations of toluenes C7 (I), C6H5 (II),
C7 (III), cycloheptatriene C7 (IV), and benzene has been studied by the method
of two‐pulse two‐colour laser photolysis of molecules in a mass spectrometer using
wavelengths 1064, 532, and 355 nm. The I ions formed due to sequential two‐photon
ionization of toluene molecules by the 266 nm radiation isomerize supposingly into
5‐methylene‐cyclohexadiene (VI). Two‐ and three‐photon stepwise dissociation of the I
and II isomers (VI and VI‐d3, respectively) induced by the 1064 nm radiation has a
resonance at the third overtone level of CH aliphatic bond stretching vibrations. Internal
energy randomization in the two‐photon dissociation is much less for VI‐d3 as compared
to VI. The mechanisms of isoenergetic dissociation (two‐ and one‐photon processes
induced by the 1064 and 532 nm radiations, respectively) are different: the one‐photon
decay via an electronically excited state proceeds considerably faster than the two‐photon
decomposition does in the ground state. The photodissociation cross sections
have been determined. It has been shown that the intensity of CH stretching vibration
overtones can be essentially higher for radical cations than for the neutral molecules.
Interaction of SF6 Multiple PhotonDissociation Products With Siliconand SiO2 Surfaces
Authors: Gorokhov Yu. A. , Gritsenko A. L. , Lokhman V. N.
Published: March 2007

Experiments on etching Si and SiO2 by the multiple photon dissociation products of
SF6 molecule in IR laser field have been carried out. These experiments showed that
the etching of Si and SiO2 is the result of two qualitatively different processes and high
selectivity (>103) can be achieved. The dependences of the etching process of the initial
gas mixture pressure and composition, on the laser intensity and the number of laser
pulses and on the direction of laser radiation have been studied. It has been found out
that the etching rates of “a monolayer per pulse” for Si and ~100 Å/min for SiO2 are
comparable to the rates achieved in low‐temperature plasma technique. Possible
mechanisms and chemical reactions which can cause Si and SiO2 etching are discussed.
It has been concluded that under the experimental conditions multiple photon dissociation
forms the basis for the etching process.
Vibrational Energy Distribution in BaI Produced inReactions of Van der Waals Molecules
Authors: Naaman R.
Published: March 2007

The reactions of Ba with CF3I dimers and CH3IAr
complexes were studied applying the laser induced
fluorescence (LIF) technique. It was found that the
BaI produced from the dimers contains about 20
kcal/mole less vibrational energy than the BaI produced
in the corresponding monomeric reaction. The
CH3IAr on the other hand, yielded only a slightly
colder vibrational distribution than the monomers.
Stimulated Processes in a Half‐collision
Authors: Telle H. H.
Published: March 2007

Selective photodissociation of diatomic molecules is
used to prepare the separating species in a well defined quantum state with narrowly determined final
kinetic energy of the particles. During the course of
separation to products the repulsive potential is
probed by a tunable dye laser, that is by induced absorption
in case the dissociation proceeds on a potential
leading to ground state products, or by induced
emission or absorption for all other cases. The determination
of interatomic potentials from the observed
spectra is discussed.
Laser Induced Chemical Reactions in Combustion and Industrial Processes
Authors: Wolfrum J.
Published: March 2007

The rapid development of powerful UV‐laser sources allows the investigation of macroscopic and microscopic details of elementary chemical reactions important in combustion processes. Experimental results on the effect of selective translational and vibrational excitation of reactants in elementary combustion reactions using laser photolysis and time‐resolved atomic line resonance absorption, laser‐induced fluorescence and CARS spectroscopy are compared with the results of theoretical studies on ab initio potential energy surfaces and thermal rate parameters. Thermal elimination of hydrogen chloride from 1,2‐dichloroethane and 1,1,1‐chlorodifluoroethane is a main industrial route to some important monomer compounds. Inducing these radical chain reactions by UV‐exciplex laser radiation offers the advantage that a monomolecular process with low activation energy becomes the rate determining step. This allows lower process temperatures with decreasing energy expense and avoiding the high temperature formation of byproducts.
Internal Energy Distribution in MgO(a3Π) Formed From Mg(3P) + O2 and N2O: A Case of Population Inversion
Authors: Bourguignon Bernard , Rostas Joelle , Taieb Guy , Gargoura Mohammed-Ali , McCombie June
Published: March 2007

The internal state distribution of MgO(a3Π) formed from Mg(3P) + O2 and N2O reactions was determined from a reanalysis of the laser induced fluorescence spectra of the d3Δ ‐ a3Π system previously published by Dagdigian. The MgO(a3Π) state formed in the reaction with O2 has a quasi‐Boltzmann distribution. In the N2O reaction the rotational excitation is much greater and the vibrational population distribution is inverted with a maximum at v = 2 ‐ 3. The a3Π rovibrational population distributions are compared with those of the X1∑+ ground state. The dynamics of these reactions are discussed on the basis of earlier ab‐initio calculations and experimental data.
Use of Lasers in Photophysical Research of Photosynthesis
Authors: Laczkó G. , Maróti P. , Szalay L.
Published: March 2007

During the past decade, extensive research has been carried out to utilize the unique characteristics of laser light. Mainly the high intensity, short pulse and small divergence of the laser beam have been made use of, and some of the results are briefly summarized here. The effect of the coherence of actinic light on the primary photochemical charge separation is discussed in some detail.
Neutral and Ionic Particle Emission From a GaAs Surface Induced by the (harmonic) Frequencies of the Nd:YAG Laser
Authors: Möhlmann G. R. , Kuzmin V. A.
Published: March 2007

The emission of ionic and neutral particles, resulting from irradiation of a GaAs surface by 1064, 532, 355 and 266 nm Q‐switched Nd:YAG laser light, has been studied. Incident laser power densities up to 9.6 × 107 Watts/cm2 have been applied. For 1064, 532 and 355 nm radiations the ratios of ionic to neutral particle emissions are close to the thermal ratio corresponding to the boiling point of Ga. In the case of 266 nm radiation this ratio appears to be higher, which is probably due to non‐thermal ion contributions. For several incident wavelengths the emitted yields of ions and neutrals varied with the fifth power of the incident laser power density. The wave form of the emitted ion pulse and the recorded mass spectrum after irradiation at 266 nm differ significantly from those obtained at the other applied wavelengths.
Practical Broad‐Band Tuning of Dye Lasers by Solvent Shifting
Authors: Grenci Susan M. , Bird George R. , Keelan Brian W. , Zewail Ahmed H.
Published: March 2007

We have operated a dye laser over a broad wavelength range (593.8–667.0 nm) by shifting the dye emission profile with incremental changes of solvent composition. This was accomplished with the laser operating continuously, and only minor adjustment of the laser optics was required. Solvent tuning was facilitated by the critical dependence of the optimum laser wavelength on concentration of the second solvent. Using the known solvent‐sensitive laser dye 9‐diethylaminobenzo[a]phenoxaz‐5‐one (DBP), 87% of the tuning range from pure xylenes to pure methanol was covered by cumulative addition of 24 vol. % methanol to the starting xylenes solution. The optimum dye concentration was found to be independent of solvent composition, so that maximum laser power could be maintained by mixing equimolar dye solutions in the two solvents. These results establish the practicality of solvent‐tuning as a method of conducting laser experiments over a broad wavelength range.
Rotationally Resolved Spectroscopy of Tetracene and its Van Der Waals Complexes With Inert Gas Atoms
Authors: van Herpen W. M. , Meerts W. Leo , Dymanus A.
Published: March 2007

Rovibronic spectra of tetracene (C18H12) and its Van der Waals complexes with argon and krypton have been resolved by using a well collimated molecular beam in combination with a single frequency dye laser. The rotational constants of tetracene have been deduced in the S0 and S1 electronic state. The rovibronic spectra of the Van der Waals complexes show an enhanced intersystem crossing.
The Investigation of Dissociation of Trifluoroacetyl Fluoride in the Field of Pulsed CO2 Laser
Authors: Aslanidi E. B. , Zarubin V. T. , Turishchev Yu. S.
Published: March 2007

CF3COF dissociation channels in the pressure region from 0.2 to 4 Torr under the pulsed CO2 laser radiation are investigated. The dissociation products COF2, C2F6, and CF4 are identified according to the infrared spectra, and their relative output is measured over the whole range of the initial substance pressures. A scheme of laserochemical reactions describing the trifluoroacetyl fluoride dissociation channels is presented. The correctness of the chosen scheme is confirmed on the basis of the elementary theory of active collisions. The measurements of CF3COF dissociation selectivity for 18O and 13C are given.
Free Rotor Styrylcyanine Chromogens
Authors: Habashy M. M. , Antonious M. S. , Abdel-Kader M. , Abdel-Mottaleb M. S. A.
Published: March 2007

Fluorescence spectra (maximum wavelength λF) and fluorescence quantum yields (φF) were measured for four structurally related styrylcyanine chromogens of the pyridinium and quinolinium type (1–4) in different solvents at ambient temperature and 77 K. The response of λF and φF values to changes in solvent polarity, solvent hydrogen bonding donor strength, viscosity and temperature was a sensitive function of chromogen structure. The sensitivities of the λF and φF values correlate with the degree of charge transfer character of the S1,CT state; Stokes shift of fluorescence was progressively decreased while φF value was enhanced as the CT character of S1,CT state increases. Moreover, a large edge‐excitation red shift was observed in ethanol glass at 77 K. The dominant photophysical features for these dyes are discussed in terms of strong emission from an intramolecular CT state characterized by different solvation sites indicated by the observation of the excitation‐wavelength dependent phenomenon in ethanol at 77 K and an important non‐radiative decay channel involving rotation of the different parts of molecules leading to a more relaxed weakly fluorescent S1,CT created in fluid media. The viscosity dependence of fluorescence properties (a marked increase in φF was observed with increasing viscosity) suggests that these dyes can be useful reporters of microviscosity for different sites in various organized assemblies. Moreover, it was suggested that increasing H‐bonding donor strength of the solvent activates a rotatory non‐radiative decay channel probably by localizing charge densities and decreasing CT nature of the S1,CT state.
The Reaction of Spin–Orbit State‐Selected Ca( PJ0  3) With CH3I, CH2I2, and SF6
Authors: Campbell Mark L. , Furio Nick , Dagdigian Paul J.
Published: March 2007

Chemiluminescence cross sections for reaction of the individual spin–orbit states of
metastable Ca() with CH3I, CH2I2, and SF6 have been determined by the use of optical pumping state selection. This technique was also used to separate the chemiluminescence arising from the two excited metastable Ca 3P0 and 1D states. The spin–orbit dependence of the chemiluminescence pathway was found to be substantial for the CH3I and CH2I2 reactions and similar to that previously observed for halogen diatom and alkyl bromide reagents. By contrast, no spin–orbit effect was observed for Ca(3P0)+SF6. These results are discussed in terms of our previously presented model for the origin of spin–orbit effects in chemical reactions.
State‐to‐State Collisional Dynamics by Coherent Laser Pulse Phase, Shape, and Frequency Modification
Authors: Banash Mark A. , Warren Warren S.
Published: March 2007

Conventional coherent pulse sequences such as photon echoes measure only highly averaged relaxation rates in complex multilevel systems, such as molecules undergoing state‐changing collisions. Pulse frequency, phase, and shape control lets us generate sequences which give a more detailed understanding of the dynamics. Results of dual frequency, crafted shape sequences on I2 are presented which show that the "coherence dephasing" time T2 is primarily due to population redistribution (energy changing collisions) in the electronically excited state, and that the electronic ground state has a much smaller cross section for such collisions. Quantitative analysis is only possible with modified laser pulse shapes which excite a single velocity component, and requires pulse sequences which correct for the hyperfine dependence of predissociation. Since this correction is rarely made in previously reported coherent transient measurements, literature values of T2 and T1 may not be reliable in the zero pressure limit.
IR MPD of CDF3 in Two‐frequency IR Fields
Authors: Bhawalkar D. D. , Chatterjee U. K. , Mittal J. P. , Nundy U. , Parthasarathy V. , Rao K. V. S. Rama , Sarkar S. K. , Shikharkhane N. S. , Puretzky A. A.
Published: March 2007

The effectiveness of various sets of laser frequencies was analyzed for two‐frequency MPD of CDF3 molecule at the different pressures of buffer gas. It was shown that MPD yield increased compared to either single‐frequency or two adjacent frequencies irradiation.
Kinetics of Nonequilibrium Gas Phase Reactions Induced by Vibrational Multiple‐Photon IR Laser Excitation of Molecules
Authors: Bagratashvili V. N. , Kuzmin M. V. , Letokhov V. S.
Published: March 2007

A simple theoretical model for the qualitative description of the kinetics of the unimolecular
decay in the pulsed IR laser field with strong deviation from thermal
equilibrium is developed. The nonequilibrium character of the reaction is introduced
by means of a special parameter of “truncation” of vibrational energy distribution
function, which takes into account depletion of the distribution function due to the
dissociation. The derived self‐consistent system of differential equations describes the
three dissociation regimes. Besides, the apparent cases of collisionless (short duration
of laser pulse τp) and equilibrium (long τp) reactions, the intermediate collisional‐nonequilibrium
dissociation is revealed. The contribution of postpulse reaction has
proved considerable in case of both long and short pulses. For the case of a successive
dissociation the possibility of synthesis of labile products which cannot be produced
at thermal initiation is established.
Photodissociation of Tetramethyltin at 193 nm
Authors: Kawasaki Masahiro , Sato Hiroyasu , Shinohara Hisanori , Nishi Nobuyuki
Published: March 2007

Tetramethyltin has been photodissociated in a molecular beam at 193 nm. The time‐of‐flight
spectrum of the methyl radicals obtained is converted into the translational energy
distribution. This distribution is well represented by a sum of two prior distributions
with restricted number of vibrational degrees of freedom, one for two‐body dissociation,
Sn(CH3)4→Sn(CH3)3 + CH3 and the other for three‐body dissociation,
Sn(CH3)4→Sn(CH3)2 + 2CH3.
Picosecond 266‐nm Multiphoton Laser Photolysis Studies on the Solvated Electron Formation Process in Water and Liquid Alcohols
Authors: Miyasaka Hiroshi , Masuhara Hiroshi , Mataga Noboru
Published: March 2007

A picosecond 266‐nm multiphoton laser photolysis method was applied to the investigation
of the solvation process of electrons in water and in several pure liquid alcohols. The
formation time of the solvated electron obtained by this method in each liquid was
revealed to be shorter than that obtained by picosecond pulse radiolysis and by the
picosecond two‐photon ionization of the solute molecules. By comparing the present
results with those obtained by other methods, the effects of the excitation energy, as well
as the solvation sphere of the relatively large parent cation on the solvated electron
formation process, were elucidated.
Oscillator Strengths of the Ultraviolet Bands of Hot and Relaxed Methallyl, Allyl, and Methyl Radicals
Authors: Nakashima Nobuaki , Yoshihara Keitaro
Published: March 2007

Absorption spectra of methallyl, allyl, and methyl radicals were measured in the ArF
laser flash photolysis of halogenated methanes and olefins, and 2‐methyl‐1‐butene.
Broad absorption spectra were detected immediately after excitation, indicating that the
radicals carried high internal energy (called “hot” radicals here). The spectra were
sharpened with time due to collisions with foreign gases and finally reached equilibrium
(spectra in relaxed states). The oscillator strengths (f) of methallyl and allyl radicals were
found to remain about the same for hot and relaxed states. The values (f) in the relaxed
states were determined with errors of ±10% to be 0.14 for the methallyl radical, 0.26 for
the allyl radical, and 1.57 × 10−2 (including the partition function) for the methyl radical.
The molar extinction coefficients of the allylic radicals were 1.4–1.8 times as great as
ones previously reported. Rate constants of collisional relaxation by nitrogen were
discussed for seven hot radicals and molecules. Larger species gave greater rate
constants. The hot methyl radical relaxed with a rate constant of 1.0 × 107s−1 in the
presence of 760 Torr of nitrogen, while for the trimethylallyl radical it was 20 times as
great as that of the methyl radical.
Internal Rotation of the MethylGroup in the ElectronicallyExcited State: o‐ andm‐Toluidine
Authors: Okuyama Katsuhiko , Mikami Naohiko , Ito Mitsuo
Published: March 2007

The fluorescence excitation and dispersed fluorescence spectra of jet‐cooled o‐ and
m‐toluidine were observed. Vibrational analysis of the spectra provided us with the
potentials for the internal rotation of the CH3 group in both ground and excited states. In
o‐toluidine, a large potential barrier to the internal rotation in the ground state is
practically removed in the excited state. On the other hand, a nearly free internal
rotation of the CH3 group in the ground state of m‐toluidine gains a large barrier by the
electronic excitation. The great change in the barrier height upon the electronic excitation is more remarkable than that found for fluorotoluene. A close relationship between the barrier height and the π electron density at the ring carbon atom was found,
indicating the hyperconjugation as the origin of the barrier height in the absence of steric
hindrance.
Definition of Photoreaction Quantum Yield at Two‐quantum Excitation of Molecules in Solution
Authors: Nikogosyan David N.
Published: March 2007

A new approach to define the photoreaction
quantum yield in case of two‐quantum excitation of
molecules in solution is proposed.
Photodissociation of CH2ClCH2Iat 308 nm
Authors: Minton Timothy K. , Nathanson Gilbert M. , Lee Yuan T.
Published: March 2007

The technique of photofragmentation translational spectroscopy has been used to study
the photodissociation of CH2ClCH2I at an excitation wavelength of 308 nm. The
exclusive dissociation pathway is C–I bond breakage with formation of CH2ClCH2 and
I(2P3/2). The centre‐of‐mass translational energy distribution of the photofragments
reveals that an average of about 50% of the excess energy appears in translation. The
angular distribution of dissociation products with respect to the laser polarization
indicates that the photodissociation process proceeds via a parallel transition—i.e., the
transition moment must be nearly parallel to the C–I bond. Exclusive production of
ground state I(2P3/2) with a parallel polarization dependence is unexpected based on the
prevailing picture for alkyl iodide photodissociation.
Millimeter‐ and Submillimeter‐wave Kinetic Spectroscopy of Reaction Intermediates
Authors: Endo Yasuki , Kanamori Hideto , Hirota Eizi
Published: March 2007

A spectroscopic method has been developed to study chemical reaction processes
through in situ observation of the time profile of molecular absorptions in the millimeter‐ and
submillimeter‐wave regions. The method has been applied to oxidation reactions of
unsaturated hydrocarbons initiated by mercury photosensitization. It has also been
combined with the excimer laser photolysis to examine photodecomposition processes
of SO2, CS2, and Cl2SO, where nascent distributions of photofragments such as SO and
CS were measured. Advantages and disadvantages of the method have been discussed in
some detail.
A Spectroscopic Study of the D() Ion‐Pair State of I2 by Optical–Optical Double Resonance
Authors: Ishiwata Takashi , Tanaka Ikuzo
Published: March 2007

The D() ion‐pair state of I2 has been analyzed by the optical–optical double resonance
(OODR) technique. In a stepwise three‐photon excitation scheme,
D()–B3Π()–X1, the D() state appeared in the OODR spectrum as the vibrational
progressions consisting of O, Q and S branches in accord with the rotational
selection rule of ΔJ = 0 and ±2 for the coherent two‐photon transition from the B3Π()
state. The D()–X1 fluorescence was resolved to determine the absolute vibrational
numbering of the D() state. We derived Dunham parameters effective for ν = 0
through ν = 124 which were used to construct a Rydberg–Klein–Rees (RKR) potential curve.
Photodissociation of Cadmium Diiodide
Authors: Kasatani Kazuo , Mori Koji , Kawasaki Masahiro , Sato Hiroyasu
Published: March 2007

Photodissociation of cadmium diiodide was studied. The nascent vibrational distribution
of CdI(X2Σ) on the photodissociation of CdI2 at 308 nm was determined by the
laser‐induced fluorescence (LIF) technique. The temporal variation in the density of
CdI(X2Σ) radicals was monitored and it was shown that second‐order recombination reactions
were important under our experimental conditions. Both the ground and the
highly excited states of cadmium atoms were generated on photodissociation of CdI2. The
multiphoton absorption process for the production of highly excited Cd atoms is discussed.
A Laser Photolysis Study of Triplet Lifetimes and of Triplet–Triplet Annihilation Reactions of Phthalocyanins in DMSO Solutions(Etude des Durées de Vie du Triplet et des Réactions d′Annihilation Triplet–Triplet de Phthalocyanines dans le DMSO par Photolyse Laser)
Authors: Debacker M. G. , Deleplanque O. , Van Vlierberge B. , Sauvage F. X.
Published: March 2007

Triplet decay of Mg and Zn phthalocyanins have been studied by laser flash photolysis as a function of concentration. The triplet decay mechanism changes from a near first order in dilute solution to an almost second order in concentrated solutions. This is interpreted in terms of triplet–triplet recombinaison. With the help of a reducing agent, it is shown that the triplet–triplet reaction can lead to charge separation.

La décroissance des états excités triplet des phthalocyanines de Mg et de Zn a été étudiée
par photolyse éclair laser en fonction de la concentration. Le mécanisme de décroissance du triplet passe d′un premier ordre presque idéal en solution diluée à un quasi second ordre en solution concentrée. Ceci s′explique par une recombinaison triplet–triplet. A l′aide d′un réducteur, la réaction triplet–triplet peut conduire à une séparation de charges.
Multiphoton and Multifrequency Resonances in the IR Laser Excitation of OsO4 Molecules Cooled in a Supersonic Jet
Authors: Evseev A. V. , Puretzky A. A. , Tyakht V. V.
Published: March 2007

The three‐frequency IR excitation of visible luminescence was used as the method for probing of the
IR multiphoton absorption of OsO4 molecules cooled in a supersonic jet. The first laser pulse
was used to form a certain vibrational distribution below the onset of vibrational quasicontinuum.
The possibility of direct excitation of the vibrational states ν = 2, 3 of pumped ν3 mode
by direct two‐ or three‐photon absorption has been shown. The excitation spectra under the influence of the
second variable laser frequency show the features attained for transitions from initially prepared vibrational
levels ν = 2 or ν = 3. The dependencies of the luminescence intensity on the IR laser fluence were
studied also to prove the role of the direct multiphoton transitions. The different multiphoton and multifrequency
resonances were analysed in the frame of simple spectroscopic model, and appropriate anharmonicity constants
were derived.
Time‐resolved Studies of Intermolecular Electronic Energy Transfer Processes between Molecules in Solution
Authors: Kaschke M. , Vogler K.
Published: March 2007

A summary of the main energy transfer (ET) mechanisms between isolated pairs of molecules in solution is presented. Various ET models for many‐molecules systems are discussed in their basic assumptions and their range of applicability. Time‐resolved studies of ET in solution allow to determine the predominant ET mechanism and to test
ET models.
Nonlinear Absorption and Far‐Infrared Generation Under the Excitation of Ammonia Molecules by Strong IR Radiation
Authors: Makarov G. N. , Sotnikov M. V. , Tyakht V. V.
Published: March 2007

We have investigated the excitation of  14NH3 molecules (the pressure is 10−2 − 1 Torr) under the effect of pulse radiation of the
CO2‐laser in a wide range of fluences (Φ = 10−3−10 J/cm2)
and detunings of the laser frequency from the absorption lines of the vibrational‐rotational transition of the ammonia
band ν2. It is shown that the efficient excitation of ammonia under the influence of nonresonance
IR radiation is due to the power broadening. In this case the calculation, which employs no fitting parameters,
describes the experimental results within experimental errors. It is shown that the abnormally high absorption
of ammonia in the case of resonance pumping is associated with an intense FIR generation which leads to elimination
of the rotational bottle neck under the excitation of molecules.
Hole Burning in the IR Predissociation Spectrum of SF6‐dimers
Authors: Heijmen B. , Liedenbaum C. , Stolte S. , Reuss J.
Published: March 2007

Hole burning experiments with two CO2 lasers have been performed to obtain insight in
the predissociation mechanism of SF6‐dimers. For the well known double peak predissociation
spectrum, always two correlated holes are observed. Strongly enhanced widths of the holes are found for dimers with higher internal energy.
Picosecond Studies of Intramolecular Double Proton Transfer by Excite‐ and Probe‐Technique
Authors: Kaschke M. , Rentsch S. , Opfermann J.
Published: March 2007

The double proton transfer of 2,2′‐bipyridyl‐3,3′‐diol (BP(OH)2) in isooctane after UV excitation has been studied by excite and probe beam spectroscopy with a time resolution of 5 ps. Estimates for the excited state proton transfer rate as well as for the extinction coefficients of the excited state absorption bands of the primarily excited species and of the tautomer have been determined.
Picosecond Absorption Spectroscopy of Polymethine Cis‐Trans Isomerization
Authors: Feller K.-H. , Gadonas R. , Krasauskas V.
Published: March 2007

Results are presented of time resolved fluorescence and absorption investigations of
DDEOCI (3,3′‐diethyl‐6,6′‐diphenyl‐9‐ethyl‐oxacarbocyanine iodide) in solvents
which differ in polarity and viscosity. The measured picosecond absorption and fluorescence
kinetics probed at various wavelengths of the polymethine dye studied can be
fitted to a double exponential decay with a minor fast component of lifetime τ1
and a major slower component of lifetime τ2. Furthermore, probing in the S1 ← S0
absorption region and in the fluorescence region results in a residual with a lifetime of some ns and
belonging to the detected red‐shifted photoisomer with a low quantum yield (φ < 10%). The lifetime and the preexponential factors of the two components are in methanolic
solution uneffected by changes of the anion.

The detected two picosecond lifetime components are supposed to belong to two isomeric species (all‐trans and mono‐cis isomer) with strongly overlapping absorption spectra.
Inter‐ and Intramolecular Vibrational Distribution in IR Multiple Photon Excitation: CF2Cl2 Molecule
Authors: Doljikov Yu. S. , Malinovsky A. L. , Ryabov E. A.
Published: March 2007

Vibrational energy distribution of IR MP‐excited CF2Cl2 is studied when pumping
molecules through ν1 and ν8 modes.
In both cases the intermolecular distribution is
found to be in a state of nonequilibrium consisting of ensembles of “hot” and “cold” molecules.
The structure of the “cold” ensemble is different when ν1
and ν8 modes
are pumped. Statistical intramolecular energy distribution caused by stochastization of vibrational motion is found
for “hot” molecules. The estimated value of stochastization onset energy
equals Eth ≤ 7800 cm−1.
Condensed Phase Laser InducedHarpoon Reactions
Authors: Fajardo Mario E. , Withnall R. , Feld J. , Okada F. , Lawrence W. , Wiedeman L. , Apkarian V. A.
Published: March 2007

Laser induced charge transfer reactions of halogens in rare gas solids and liquids provide
a powerful means for the study of condensed phase dynamics. Many‐body effects with
respect to both electronic and nuclear coordinates, and cooperative interactions with
radiation fields, are some of the studied phenomena that are highlighted in this article.

The pertinence of these ionic reactions to chemistry in solids is demonstrated in
photodissociation studies of molecular halogens in rare gas matrices. The coexistence of
both delocalized and localized charge transfer states in solid xenon doped with atomic
halogens is presented and dynamical consequences—charge separation, self‐trapping
and energy storage—are discussed. Static and dynamic solvent effects in liquid phase
harpoon reactions are considered. The characterization of cooperative excitations—
two‐photon, two‐electron transitions—in liquid solutions is presented.
Photochemical Chain Reactionsin Amorphous Solids
Authors: Sedlacek Arthur J. , Wight Charles A.
Published: March 2007

In this article, we review recent work in the authors′ laboratory on the subject of free
radical chain reactions of chlorine with small hydrocarbons in amorphous solids. The
solids are formed as thin films by spray deposition of the gaseous reagents onto a
cryogenic window. Reactions are initiated by excimer laser photolysis at 308 nm, which
dissociates a small fraction of the chlorine molecules to atoms. Product yields and
branching ratios are determined by infrared absorption spectroscopy. Reactions of
chlorine with cyclopropane or cyclobutane proceed by true chain reactions, as evidenced
by high product quantum yields (number of product molecules formed per laser photon
absorbed by the sample). Measurements of the dependence of the product yield on the
relative concentrations of chlorine and hydrocarbon provide clues to the reaction
mechanism in the solid state. The cyclobutane reaction appears to involve H atom
transfer from cyclobutane to cyclobutyl radical as an intermediate step in the overall
reaction. Reaction of chlorine with propane, n‐butane, or isobutane does not appear to
involve chain propagation and is dominated by radical recombination processes which
result in low quantum yields. All of these results are discussed in terms of reactions
which occur in a solid state environment where molecular motion is severely restricted.
Laser Stimulation andObservation of Simple GasPhase Radical Reactions
Authors: Wolfrum J.
Published: March 2007

Experiments on the effect of Selective vibrational, translational and orientations excitation
of reactants in bimolecular reactions can give important insights into the microscopic
dynamics of elementary chemical reactions. The information obtained in such
experiments can be compared with the results of theoretical calculations of the reaction
dynamics based on ab initio potential energy surfaces and is also of basic interest to
improve the kinetic data used in detailed chemical kinetic modelling.

Rotational and vibrational energy transfer between H2 and H0 has been studied
directly using Raman excitation combined with time resolved CARS spectroscopy. The
competition between reactive and inelastic channels was investigated for reactions of
atoms with vibrationally excited H2 and HCl molecules. Selective vibrational excitation
was achieved by using infrared laser or Raman‐pumping. The reaction products were
detected by time resolved atomic line resonance absorption mass‐spectrometry and
CARS‐spectroscopy. In some cases information on the contributions of adiabatic and
non‐adiabatic reactive pathways could be obtained. The reaction H + O2→ OH + O has
been studied using translationally hot H atoms at various energies. Absolute total
reactive cross‐sections, nascent rotational state distributions and information on the
distribution of orientations of the OH angular momentum vector using polarized
dissociation and analysis laser sources have been obtained.
The 355 nm Photolysis of Methyl Nitrite
Authors: Atkins C. G. , Hancock G.
Published: March 2007

Single photon laser induced fluorescence (LIF) has been used to study the NO fragment
produced in its ground electronic state from the 355 nm photolysis of CH3ONO.
Populations of rotational, vibrational, spin‐orbit and lambda doublet components have
been measured. The results are in broad agreement with previous two photon LIF
studies, and confirm the dynamics of the process in which the NO fragment departs from
an essentially planar CONO framework with non‐statistical energy partitioning in the
internal states of the products.
The Physical State of Clusters.An Infra‐red Laser Study ofSmall Cyclopropane andDimethylcyclopropane Clusters
Authors: Crooks J. J. , Stace A. J.
Published: March 2007

Infrared absorption profiles have been measured for cyclopropane and 1,1‐dimethylcyclopropane
clusters by monitoring the depletion of signal intensity in a mass spectrometer
as a function of laser wavelength. Data have been obtained for (C3H6)n+ with n
in the range 2–15, and for (C5H10)n+ with n equal to 2 and 5. A comparison between the
cluster results and available infrared data on the various bulk‐phase states of both
cyclopropane and 1,1‐dimethylcyclopropane, suggests that the clusters are liquid‐like.
(2 + 2) Resonance EnhancedMultiphoton Ionization Spectra ofJet‐Cooled ortho‐, meta‐ andpara‐Xylene
Authors: Blease T. G. , Donovan R. J. , Langridge-Smith P. R. R. , Ridley T.
Published: March 2007

Two‐photon spectra of the S1(Ã)–S0() transition of jet‐cooled ortho‐, meta‐ and
para‐xylene have been recorded in the region 43,000–37,000 cm−1 using resonance
enhanced multiphoton ionization excitation. A full vibronic analysis for all three isomers
has been carried out enabling the identification of several excited state vibrational
frequencies for the first time. In particular, for ortho and para substitutions, a new,
strong two‐photon vibronic coupling mode ν19b has been identified, and the significance
of this result is discussed. Some anomalies in the assignment of previously published
spectra of the xylenes, and related disubstituted benzenes, have been observed and
reassignments are suggested. In addition we show that the comparison of one and
two‐photon spectra provides a method for determining the mechanism by which totally
symmetric fundamentals gain their intensity in one‐photon spectra, namely either from
Herzberg–Teller intensity stealing or due to favourable Franck–Condon overlap.
Reactive Scattering of OxygenAtoms With Bromine Molecules
Authors: Firth N. C. , Keane N. W. , Smith D. J. , Grice R.
Published: March 2007

Reactive scattering of O atoms with Br2 molecules has been studied at an initial
translational energy E~35 kJ mol−1 using cross‐correlation time‐of‐flight analysis with
resolution improved over previous measurements. The centre‐of‐mass differential cross
section peaks in the forward and backward directions with a higher product translational
energy for backward Scattering. The angular distribution traced at the peak of the
product velocity distribution peaks more sharply in the forward than the backward
direction but the angular distribution of product flux shows a distribution which is more
nearly symmetrical about θ = 90°. The observed scattering is attributed to a triplet
OBrBr complex intermediate with a lifetime which is shorter than the period of overall
rotation of the axis of the heavy BrBr diatomic but which is long compared with the
period of vibrational and rotational motion of the light O atom.
Laser Induced Fluorescence of4‐N,N‐Dimethylaminobenzonitrile(DMABN) and RelatedCompounds
Authors: Jones Anita C. , Phillips David
Published: March 2007

The role of polar solvent in determining the photophysics of normal (b*) and anomalous
(a*) fluorescence from 4‐N,N‐dimethylaminobenzonitrile (DMABN) and related compounds
has been investigated by means of picosecond time‐resolved fluorescence studies
in non‐polar/polar solvent mixtures, and by electronic spectroscopic studies on complexes
of 1:1 stoichiometry prepared by nozzle expansion. The solution phase results
indicate clearly that a DMABN‐polar solvent complex is formed initially in either
ground or excited state, and that this rearranges to a geometry from which the b* to a*
state transition can occur. Specific solvent‐solute interactions are clearly indicated by
this work, and these lead to the necessity of modelling b* state decay kinetics in solution
by a distribution of decay times.

Laser induced fluorescence studies of jet‐cooled solvated complexes of DMABN and
the related molecule 4‐aminobenzonitrile (4‐ABN) provide evidence for the existence of
1:1 complexes involving interaction of a protic solvent molecule with either the cyano
group or the amino group. In the case of 4‐ABN both types of complex are fluorescent
whereas in the case of DMABN, those complexes involving interaction with the
dimethylamino group appear to be non‐emissive. This behaviour may be due to
formation of DMABN‐solvent exciplex which constitutes a dark state under jet‐cooled
conditions. Neither the DMABN bare molecule nor the observed 1:1 solvated complexes
exhibit a* emission in the jet.
The Production of IF(B3Π) in the248 nm Laser Photolysis ofFluorine/Alkyl Iodide Mixtures
Authors: Raybone D. , Watkinson T. M. , Whitehead J. C. , Winterbottom F.
Published: March 2007

Sustained visible emission in the region 440–850 nm from the B → X system of IF is
observed when a gas phase mixture (~0.5 mbar) of an alkyl iodide with F2 in He is
photolysed at 248 nm by a KrF laser. The total intensity and decay rate of the IF(B)
emission is a strong function of the identity of the alkyl iodide and can be correlated with
the 248 nm photon yields for the production of I*(2p1/2). The half‐lives for the IF(B)
decays range from 5 μs for t‐C4H9I to 770 μs for n‐C3F7I. Decay curves for the I*(2p1/2)
concentrations are also measured by atomic fluorescence. The mechanism for IF(B)
formation in these systems is discussed and it is suggested that IF(B) is produced either
by a recombination process involving I* and F atoms or by multistep collisional
excitation of ground state IF(X) by I*. The F atoms can be produced following the
photolysis pulse by the reaction of the alkyl radical with molecular fluorine and IF(X)
can result either from the reaction of F atoms with the alkyl iodide or from a dark
reaction between molecular fluorine and the alkyl iodide.
Elementary Rate Processes in theDissociative CO for C2H4Substitution Reactions ofOrganometallic Complexes in theGas Phase
Authors: Duray Steven J. , Becher Dawn M. , Grant Edward R.
Published: March 2007

Dissociative substitution mechanisms abound in organometallic chemistry. For certain
systems, such processes can be isolated in the gas phase, where, as sequences of
elementary unimolecular and bimolecular reactions, their kinetics can convey information
on fundamental energetics and dynamics of metal‐centered chemical transformations.
Methods of competitive kinetics, using time‐resolved infrared absorption
spectrometry, provide relative and absolute rate constants for comparatively fast
reactions. Work yielding unimolecular decay and relative bimolecular production rate
constants for selected bis‐ and tris‐ethylene complexes of iron and chromium carbonyls is
summarized together with a report of new work on the CO‐for‐C2H4 substitution
kinetics of (C2H4)Cr(CO)5.
Making Light Work—Applicationsof Lasers to Chemical Production
Authors: Hackett Peter A.
Published: March 2007

This review considers several applications of photochemistry to the synthesis of chemicals
by industry. Factors relevant to the use of lasers by industry in the synthesis of
specific chemicals are also considered.
Transition Metal Ion Complexation and Extraction by HydroxamateFunctionalised p‐Tert‐Butylcalix[4]Arenes
Authors: Glennon Jeremy D. , Horne Elizabeth , O′Sullivan Patricia , Hutchinson Sharon , McKervey M. Anthony , Harris Stephen J.
Published: March 2007

The functionalisation of macrocyclic p‐tertbutylcalix[4]arenes at the lower rim with
hydroxamic acid and proline hydroxamic acid groups gives the calixarenes chelating
properties similar to siderophores. The  1H NMR spectrum of p‐tertbutylcalix[4]arene
tetrahydroxamic acid shows a broad band at 10.8 ppm in DMSO‐d6 attributed to NHOH protons. Diffuse reflectance spectral analysis of PVC membranes containing the
calixarene hydroxamic acids show absorption bands at 485 nm and 504 nm following
contact with aqueous solutions of Fe(III) and V(V) respectively. The pH dependency of
this extractive selectivity is examined for Fe(III), Co(II), Pb(II), Mn(II), Cu(II) and Ni(II)
using a solid phase extraction approach. Spectrophotometric evidence for the
complexation of Cu(II) in methanol by p‐tertbutylcalix[4]arene tetraproline acid is also
provided.
Degradation of Anthracycline Antitumor Compounds Catalysed by Metal Ions
Authors: Fiallo Marina M. L. , Haj Hayet Tayeb-Bel , Garnier-Suillerot Arlette
Published: March 2007

The influence of some metal ions on the degradation of anthracyclines was examined. One of the
degradation products is the 7,8‐dehydro‐9,10‐desacetyldoxorubicinone, D* (¥), usually formed by
hydrolysis at slightly basic pH. D* is a lipophilic compound with no cytostatic properties. Its formation
could be responsible for the lack of antitumor activity of the parent compound. The coordination of
metal ions to anthracycline derivatives is required to have degradation products. Cations such as
Na+, K+, or Ca2+ do not induce the D* formation however metals which can form stable complexes
with doxorubicin afford D*. Iron(III) and copper(II) form appreciable amount of D* at slightly acidic pH.
Terbium(III) forms D* but its complex is stable only at slightly basic pH. Palladium(II) which does not
form D*. The influence of the coordination mode of metal ions to anthracycline on the D* formation
is discussed.
An Investigation of 2′‐Deoxyribonucleoside Cyanoboranes in Mice forTherapeutic Safety
Authors: Hall Iris H. , Burnham Bruce S. , Rajendran K. G. , Chang J.-J. , Sood Anup , Spielvogel Bernard
Published: March 2007

A standard acute toxicity study was undertaken to assess 2′‐deoxyribonucleoside
cyanoboranes for therapeutic safety. 2′‐Deoxyribonucleoside cyanoboranes and related
derivatives were nontoxic at doses required for anti‐neoplastic and hypolipidemic activities.
At higher doses (50 and 100 mg/kg/day IP for 7 days), all treated animals survived with
slight reductions in total body weight and small decrements in daily food consumption. No
clinical chemistry value was elevated to a magnitude suggesting onset of organ specific
toxicity. However, agents appeared to modulate subpopulations of white blood cells, ,
more lymphocytes than PMNs were present in blood from treated animals as determined by
differential cell counts. This modulation is correlated with increases in granulomatous foci in
the spleen and mesentery of treated animals after 7 days. The kidney was damaged only by
Compound at 50 and 100 mg/kg/day; Compound had the most potent anti‐neoplastic
activity. The compounds demonstrated no toxicity against human HCT‐8 ileum cells.
LD50 values were greater than 1000 mg/kg, IP, for all compounds.