IR multiple-photon decomposition of 1,1,1-trifluoroacetone has been achieved in bulk by irradiating molecules with 970.55 cm&#x2212;1 laser radiation. In collisional regime the onset of laser induced breakdown has been observed. Primary fragmentation and subsequent ion and radical secondary reactions have been monitored detecting the spontaneous luminescence with a gateable Optical Multichannel Analyzer.

R. Fantoni

E. Borsella

S. Piccirillo

A. Giardini-Guidoni

R. Teghil

IR Photodecomposition of CH3COCF3

V. S. Letokhov

Editorial

Laser irradiation of R(&#8211;) carvone in solution in acrylonitrile within the absorption band
of its <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>n</mml:mi><mml:mo>&#x2212;</mml:mo><mml:msup><mml:mi>&#x03C0;</mml:mi><mml:mo>*</mml:mo></mml:msup></mml:mrow></mml:math>
 transition (&#8771;350 nm) leads to the formation of cyclobutanic adducts, together with traces of camphocarvone.The carvone transformation is complete and appears with high quantum efficiency.
The quantum yield for intermolecular reaction is intensity dependent (13&#8211;30&#37;). This is ascribed to the fact that the reaction takes place via both a one and a two-photon absorption channel, the second being even more efficient.

R.  Stringat

F.  Lemaire

R.  Fellous

A. M. Loiseau

Laser Induced Synthesis: Condensation of Acrylonitrile on Carvone

The double proton transfer of 2,2&#39;-bipyridyl-3,3&#39;-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.

M.  Kaschke

S.  Rentsch

J.  Opfermann

Picosecond Studies of Intramolecular Double Proton Transfer by Excite- and Probe-Technique

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.

B.  Heijmen

C.  Liedenbaum

S.  Stolte

J.  Reuss

Hole Burning in the IR Predissociation Spectrum of SF6-dimers

Vibrational energy distribution of IR MP-excited CF2Cl2 is studied when pumping
molecules through &#957;1 and &#957;8 modes. 
In both cases the intermolecular distribution is 
found to be in a state of nonequilibrium consisting of ensembles of &#8220;hot&#8221; and &#8220;cold&#8221; molecules. 
The structure of the &#8220;cold&#8221; ensemble is different when &#957;1 
and &#957;8 modes 
are pumped. Statistical intramolecular energy distribution caused by stochastization of vibrational motion is found 
for &#8220;hot&#8221; molecules. The estimated value of stochastization onset energy 
equals Eth &#8804; 7800 cm&#8722;1.

Yu. S. Doljikov

A. L. Malinovsky

E. A. Ryabov

Inter- and Intramolecular Vibrational Distribution in IR Multiple Photon Excitation: CF2Cl2 Molecule

The dynamics of excitation by CO2 laser pulses of SF6 molecules from individual
rotational sublevels J&#8243; of the ground vibrational state have been investigated in a pulsed
molecular jet under essentially collisionless conditions. At different energy fluences of exciting laser pulse &#x03A6; = 10&#8722;5 + 10&#8722;1 J/cm2, the dependences of the fraction <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>f</mml:mi><mml:mi>J</mml:mi></mml:msub></mml:mrow></mml:math> of excited molecules on the rotational quantum number J&#8243; have been obtained, 
when SF6 molecules were excited on the 10P(16) CO2 laser line, as well as on the 10P(18) and
10P(14) lines at &#x03A6; = 0.1 J/cm2. Comparison of experimental results with theoretical 
predictions18&#8211;20 shows rather strong disagreement between theory and experiments both 
in the population of the &#965;3 = 1 state and in the role of multiphoton transitions. 
It is shown that the narrowing of the exciting laser pulse spectrum (the 10P(16) line, 
&#x03A6; &#8818; 10&#8722;2 J/cm2) results in drastic decrease of the fraction of excited 
molecules from the (&#965;3 = 0, J&#8243; = 4) state which is most resonant with laser 
radiation.

Yu. A. Kuritsyn

G. N. Makarov

I.  Pak

M. V. Sotnikov

I. I. Zasavitsky

A. P. Shotov

Diode Laser Spectroscopy of the Dynamics of Multiphoton Excitation of SF6 Molecules by
CO2 Laser Pulses

Laser dyes with terphenyl and quaterphenyl as the fluorophors and with acyclic ether auxofluors 
			were improved when the ether groups were made cyclic. Dyes containing cyclic ethers in 5- and 6-membered 
			rings were observed to lase in the 360&#8211;400 nm region with better lifetime and/or solubility than their 
			acyclic analogs. In one case the laser output wavelength of a quaterphenyl fitted with cyclic ether auxofluors 
			was red-shifted enough to match the wavelength of a sexiphenyl without auxofluors.

Joel M. Kauffman

Charles J. Kelley

Alem  Ghiorghis

Edward  Neister

Lorne  Armstrong

Cyclic Ether Auxofluors on Oligophenylene Laser Dyes

The dissociation yield and branching ratio in CO2 laser-induced infrared multiphoton dissociation 
(IRMPD) of CF3CHClF were investigated by irradiation at 9R(20) 1078.6 cm&#8722;1 under 
an unfocused irradiation geometry (0.75-2.3 J/cm2) and a mildly focused one (1.2-18 J/cm2). By using a Br2-scavenging technique, it was revealed that the primary dissociation of CF3CHClF proceeded mainly via three-centered HCl molecular elimination and C-Cl bond rupture, with minor contributions of C-C bond rupture and HF molecular elimination at higher fluences. The secondary photolysis of the primarily produced species during the laser pulse to yield CF2 and CClF carbenes depended strongly upon the laser fluence.

Shuji  Kato

Yoshihiro  Makide

Takeshi  Tominaga

Kazuo  Takeuchi

Infrared Multiphoton Dissociation of CF3CHC<small.letters>l</small.letters>F: 
 Primary Dissociation and Secondary Photolysis

A simple, realistic model is developed to take into account kinematic effects on
laser-induced fluorescence (LIF) measurements in crossed beam reactive scattering
experiments. The conversion factor from nascent populations to measured densities
(which are proportional to the LIF intensity) is calculated for several cases of practical
interest. The density-flux transformation proposed by Zare and coworkers arises from
the model as a limiting case. Results concerning the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>C</mml:mtext><mml:mo>+</mml:mo><mml:mtext>NO</mml:mtext><mml:mo>&#x2192;</mml:mo><mml:mtext>CN</mml:mtext><mml:mo>+</mml:mo><mml:mtext>O</mml:mtext></mml:mrow></mml:math>
 reaction, studied in a pulsed crossed supersonic beam experiment, are also included. Calculations
carried out under various conditions emphasize the dramatic importance of beam collimation and pulse duration on detection efficiency.

Christian  Naulin

Michel  Costes

Asmae  Benseddik

G&#233;rard  Dorthe

Kinematic Effects on Laser-induced Fluorescence Measurements Performed in Reactive Crossed Beam Experiments

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