Laser pyrolysis of CH3Br by a strong laser irradiation was studied in this work. Besides a fine needle ofsolid carbon was deposited at the surface on the substrate, HBr and CH4, were found as gaseous productswith a ratio of 2:1. Small amount of C2H2 was also detected. The variation in the pressures of CH3Br,HBr and CH4 were measured by Raman spectroscopy. It indicated that the decomposition of CH3Br wasfirst order with respect to CH3Br. The reaction mechanism of the laser pyrolysis was suggested as follows:After gaining enough energy at the hot spot, CHaBr was pyrolyzed to produce HBr and CH2 which thenreacted with CH3Br to form CH4, and solid carbon.

Hua  Chang

Jang Ching Hsieh

Laser Pyrolysis of CH3Br

Excitation and fluorescence spectra of benzonitrile-benzene and toluene complexes seeded in helium and
expanded in a supersonic free jet reveals two types of transition attributed to the coexistence of two
isomeric forms. One consists of narrow bands in both excitation and emission and is characteristic of
wealdy perturbed van tier Waals complexes. The other involves broadened absorption and gives rise to an
exciplex type emission.

F.  Lahmani

C.  Lardeux-Dedonder

A.  Zehnacker

Spectroscopy and Dynamics of Benzonitrile-Enzene Complexes in A Supersonic Free-Jet

Ahmed H. Zewail

Introduction

V. N. Bagratashvili

V. S. Letokhov

A. A. Makarov

E. A. Ryabov

Multiple-Photon Infrared Laser Photophysics and Photochemistry. II

The deactivation process of J-aggregates of DDEOCI (3,3&#39;-diethyl-5,5&#39;-diphenyl-9-ethyl-oxacarbocyanine
iodide) was investigated by means of steady-state and time-resolved absorption and fluorescence
spectroscopy. The decay kinetics as well as the transient absorption spectra have been analyzed including
different aggregate structures and exciton-exciton annihilation.

K.-H.  Feller

R.  Gadonas

V.  Krasauskas

V.  Fidler

S.  Vajda

Time-Resolved Spectroscopy of Polymethine J-Aggregates

The emission of gas phase particles from a GaAs surface, due to irradiation at 1064 nm
by an unfocussed Q-switched Nd:YAG laser beam, has been studied. Mass spectra
have been recorded with the aid of a quadrupole mass spectrometer, and the ion-neutral
ratio of the emitted particles has been measured with an electrical diode set up. The
applied incident laser radiation power density was varied in the range 1.2&#x2013;9.6 &#xD7; 107
Watts/cm2 and was delivered as 10 ns (fwhm) long pulses. It appeared that mainly Ga
atoms and As2 molecules were emitted, together with minor amounts (&#x3C;1&#x25;) of Ga2
and GaAs molecules. Besides the emission of neutral particles, the formation of Ga+
atomic ions was observed. By measuring the ratio of Ga+ ions and Ga neutral atoms
it could be shown that the (ionic) particle emission is governed by a thermal mechanism
for 1064 nm incident radiation. This latter experimental result differs from that obtained
if a ruby laser (694 nm) is used as the radiation source.

G. R. M&#xF6;hlmann

Neutral and Ionic Particle
Emission Produced by Laser
Irradiation of a GaAs Surface

Investigations of the collisional interactions between sodium atoms in the 32P states and helium and hydrogen gases are described. Studies of collision-induced mixing and quenching interactions have been carried out under conditions where chemical reaction to produce sodium hydride is possible. Thus the sodium number derivatives are sufficient for radiation trapping to occur. This is in contrast to virtually all previous investigations in which conditions were such that this effect need not be considered. The intensity and temporal behaviour of laser induced fluorescence (LIF) resulting from the photoexcitation of the sodium 32P states is monitored as a function of foreign gas pressure. Whilst many of the features observed are to be expected, results show how radiation trapping strongly influences cross-section determination. The need for a more rigorous treatment of collision cross-sections under these conditions, which are often more realistic than the &#8216;ideal&#8217; trapping free situations, is demonstrated.

L. H. Vassie

H. H. Telle

Radiative Lifetimes and Collision Processes in Sodium-Rare Gas and Sodium-Hydrogen Systems

Anthony W. Parker

Preface

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&#8211;triplet recombinaison. With the help of a reducing agent, it is shown that the triplet&#8211;triplet reaction can lead to charge separation.La d&#233;croissance des &#233;tats excit&#233;s triplet des phthalocyanines de Mg et de Zn a &#233;t&#233; &#233;tudi&#233;e
par photolyse &#233;clair laser en fonction de la concentration. Le m&#233;canisme de d&#233;croissance du triplet passe d&#39;un premier ordre presque id&#233;al en solution dilu&#233;e &#224; un quasi second ordre en solution concentr&#233;e. Ceci s&#39;explique par une recombinaison triplet&#8211;triplet. A l&#39;aide d&#39;un r&#233;ducteur, la r&#233;action triplet&#8211;triplet peut conduire &#224; une s&#233;paration de charges.

M. G. Debacker

O.  Deleplanque

B.  Van Vlierberge

F. X. Sauvage

A Laser Photolysis Study of Triplet Lifetimes and of Triplet&#8211;Triplet Annihilation Reactions of Phthalocyanins in DMSO Solutions
(Etude des Dur&#233;es de Vie du Triplet et des R&#233;actions d&#39;Annihilation Triplet&#8211;Triplet de Phthalocyanines dans le DMSO par Photolyse Laser)

A. Gonz&#xE1;lez Ure&#xF1;a

Laser Chemistry in Spain

About this journal

Journal profile

Meet the editorial board

Editor spotlight

Submit your proposal

Do you think there is an emerging area of research that really needs to be highlighted? Or an existing research area that has been overlooked or would benefit from deeper investigation? Raise the profile of a research area by leading a Special Issue.

Laser Chemistry