Collisions that produce a change in the total angular-momentum and quenching processes involving the
triplet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>Z</mml:mi><mml:mn>3</mml:mn></mml:msup><mml:msup><mml:mi>F</mml:mi><mml:mn>0</mml:mn></mml:msup></mml:mrow></mml:math> titanium excited level and diatomic molecules have been studied by laser perturbation and
time-resolved spectroscopy. The thermally averaged total angular-momentum changing cross sections
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msup><mml:mi>z</mml:mi><mml:mn>3</mml:mn></mml:msup><mml:msubsup><mml:mi>F</mml:mi><mml:mi>i</mml:mi><mml:mn>0</mml:mn></mml:msubsup><mml:mo>&#x2192;</mml:mo><mml:msup><mml:mi>z</mml:mi><mml:mn>3</mml:mn></mml:msup><mml:msubsup><mml:mi>F</mml:mi><mml:mi>j</mml:mi><mml:mn>0</mml:mn></mml:msubsup></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> in units of <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>16</mml:mn></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msup><mml:mtext>&#x2009;</mml:mtext><mml:mtext>are:</mml:mtext><mml:mtext>&#x2009;</mml:mtext><mml:msub><mml:mover accent="true"><mml:mi>&#x03C3;</mml:mi><mml:mo>&#x00AF;</mml:mo></mml:mover><mml:mrow><mml:mn>42</mml:mn></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>3.2</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>1</mml:mn><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mn>1.4</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>0.5</mml:mn><mml:mo>;</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:msub><mml:mover accent="true"><mml:mi>&#x03C3;</mml:mi><mml:mo>&#x00AF;</mml:mo></mml:mover><mml:mrow><mml:mn>43</mml:mn></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>13.3</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>2</mml:mn><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mn>6.8</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>1</mml:mn><mml:mo>;</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:msub><mml:mover accent="true"><mml:mi>&#x03C3;</mml:mi><mml:mo>&#x00AF;</mml:mo></mml:mover><mml:mrow><mml:mn>32</mml:mn></mml:mrow></mml:msub><mml:mtext>&#x2009;</mml:mtext><mml:mo>=</mml:mo><mml:mn>19.0</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>2</mml:mn><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mn>7.2</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>
, respectively, for nitrogen and hydrogen colliding partners.Large quenching cross sections are obtained, as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mover><mml:mi>&#x03C3;</mml:mi><mml:mo>&#x2212;</mml:mo></mml:mover></mml:mrow><mml:mi>Q</mml:mi><mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>53</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>7</mml:mn></mml:mrow></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mover><mml:mi>&#x03C3;</mml:mi><mml:mo>&#x2212;</mml:mo></mml:mover></mml:mrow><mml:mi>Q</mml:mi><mml:mrow><mml:msub><mml:mi>H</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>38</mml:mn><mml:mo>&#x00B1;</mml:mo><mml:mn>4</mml:mn></mml:mrow></mml:math> in units of 10<sup>-16</sup> cm<sup>2</sup>.
These results are discussed in relation with previous measurements dealing with titanium-noble-gas
collisions, and with available published results.

V.  Quichaud

D.  D&#233;zert

J.  Aubreton

D.  Degout

A.  Catherinot

Change In Total Angular Momentum Within The <svg style="vertical-align:-0.0pt" height="15.8375" version="1.1" viewBox="0 0 35.625 15.8375" width="35.625" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,15.775)"><path id="x1D44D" d="M698 636l-541 -596q60 -5 176 -5q91 0 138.5 5t69.5 24q44 36 85 124l29 -15q-38 -125 -64 -173h-559l-9 16l545 598h-182q-81 0 -109 -8t-48 -31q-26 -29 -55 -103l-29 3q23 86 42 200h22q11 -16 21 -20.5t34 -4.5h428z" /></g><g transform="matrix(.012,-0,0,-.012,12.313,7.613)"><path id="x33" d="M285 378v-2q65 -13 102 -54.5t37 -97.5q0 -57 -30.5 -104.5t-74 -75t-85.5 -42t-72 -14.5q-31 0 -59.5 11t-40.5 23q-19 18 -16 36q1 16 23 33q13 10 24 0q58 -51 124 -51q55 0 88 40t33 112q0 64 -39 96.5t-88 32.5q-29 0 -64 -11l-6 29q77 25 118 57.5t41 84.5&#xA;q0 45 -26.5 69.5t-68.5 24.5q-67 0 -120 -79l-20 20l43 63q51 56 127 56h1q66 0 107 -37t41 -95q0 -42 -31 -71q-22 -23 -68 -54z" /></g><g transform="matrix(.017,-0,0,-.017,18.65,15.775)"><path id="x1D439" d="M599 650l-18 -160l-30 -2q-2 70 -11 94q-5 16 -26 24t-75 8h-94q-27 0 -33.5 -6.5t-12.5 -32.5l-43 -226h108q52 0 72.5 5t31 18t28.5 52h28l-40 -200h-28q-1 42 -6 56.5t-24.5 21t-70.5 6.5h-108l-32 -177q-13 -65 1 -80.5t88 -22.5l-8 -28h-279l6 28q61 5 77.5 20.5&#xA;t29.5 81.5l72 387l7.5 40.5t1 26.5t-4 18t-15.5 10t-24 6t-37 4l8 28h461z" /></g><g transform="matrix(.012,-0,0,-.012,29.225,7.613)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105&#xA;q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g></svg> Titanium Excited State
Induced By Collisions With Hydrogen And Nitrogen Molecules

The study of IR MPD of HCIC=CBCI<sub>2</sub>H molecule by CO<sub>2</sub>.-laser is presented. We provide experimental
results showing high degree of fragmentation of this molecule (down to elementary boron) during
nonequilibrium laser induced radical bimolecular reactions.

G. I. Abdushelishvili

T. G. Abzianidze

A. G. Bakhtadze

P. D. Kervalishvili

G. I. Tkeshelashvili

T. B. Tzinadze

Boron Particles Production in
Nonequilibrium Laser-Chemical Radical
Reactions During the IR Multiphoton
Dissociation of HCIC=CBCI<sub>2</sub>H Molecules

With reference to recent laser investigations of excited state reactions of maleic acid in Letokhov’s group,
relevant excited state constants were determined by means of a physico-mathematical methods package of
nonlinear absorption and the excited state populations were calculated for the experimental conditions.
Based on this, a change of the assignment of the found reactions to excited states is suggested in the
following manner: dimerization in T<sub>1</sub> and maleic acid formation in a higher excited triplet.

D. Leupold

J. Ehlert

S. Oberl&#xE4;nder

E. Klose

S. Mory

G. Winkelmann

Nonlinear Laser Chemistry of Maleic Acid

The photochromism of N-phenyl-rhodaminelactame (3&#39; ,6&#39; -bis-(diethylamino)-2-phenyl-spiro[1H-isoindole-1,9&#39;[9H] Xanthaen]-3-[2H]-one) was investigated in solutions of acetonitrile, dioxane and
mixtures of dioxane with H<sub>2</sub>0, methanol and ethanol by laser flash time resolved absorption measurements.
The colouring reaction kinetics and the relative quantum yield of the red product were measured
using nanosecond excimer laser excitation at 308 nm. In most cases, first order kinetics was.observed. The
first order rate constants and the quantum yield were found to be dependent on the solvent and the
number of laser pulses that had previously irradiated the solution. The thermal fading reaction occurred
on a millisecond timescale and showed large deviations from first order kinetics in all solvents. In addition,
picosecond laser pulses at 285 nm were used to measure the fluorescence lifetime of the S<sub>1</sub> state of
the rhodamine derivative with picosecond resolution. Single exponential decays were observed in all
solvents and the lifetime ranged between 3 and 6 nanoseconds. We conclude that the photoreaction does
not proceed directly from the S<sub>1</sub> state, and propose a mechanism for the photochromic process, in which
an intermediate decomposes to rotameric isomers of the coloured product, which are not equilibrated on
the millisecond time scale of the reverse reaction.

H.  Willwohl

J.  Wolfrum

R.  Gleiter

Kinetics and Mechanism of the Photochromism of N-Phenyl-Rhodaminelactame

Relative values of the total chemiluminescence cross.section for the crossed molecular beam <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Ca</mml:mtext></mml:mrow><mml:mo>&#x2217;</mml:mo></mml:msup><mml:mo>+</mml:mo><mml:msub><mml:mrow><mml:mtext>SF</mml:mtext></mml:mrow><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2192;</mml:mo><mml:msup><mml:mrow><mml:mtext>CaF(A</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msup><mml:mi>&#x03A0;</mml:mi><mml:msub><mml:mrow><mml:mtext>)+SF</mml:mtext></mml:mrow><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math> reaction have been measured as a function of collision energy. Both metastable calcium
atom states <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi></mml:mi><mml:mn>3</mml:mn></mml:msup><mml:msup><mml:mi>P</mml:mi><mml:mn>1</mml:mn></mml:msup></mml:mrow></mml:math>
 were produced by low voltage de-discharge while translational excitation of the SF<sub>6</sub>
beam was achieved via the seeding technique. Whereas chemiluminescence yield from the <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>CaF(A</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msup><mml:mi>&#x03A0;</mml:mi><mml:mtext>)</mml:mtext></mml:mrow></mml:math> was
observed from both of the metastable atom reactions, no chemiluminescence signal was detected from the
ground atom reaction even though enough translational excitation was used to produc.e that excited
product. By changing the discharge conditions different metastable concentrations were produced to
measure the state-to-state cross-section for both <sup>3</sup>P and <sup>1</sup>D reactions, as a function of collision energy, up
to 0.6 eV. Laser induced fluorescence of the atomic 4s5s <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi></mml:mi><mml:mn>3</mml:mn></mml:msup><mml:msub><mml:mtext>S</mml:mtext><mml:mn>1</mml:mn></mml:msub><mml:mo>&#x2190;</mml:mo><mml:mn>4</mml:mn><mml:mi>s</mml:mi><mml:mn>4</mml:mn><mml:mi>p</mml:mi></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi></mml:mi><mml:mn>3</mml:mn></mml:msup><mml:msub><mml:mtext>P</mml:mtext><mml:mrow><mml:msup><mml:mi>J</mml:mi><mml:mo>&#x2218;</mml:mo></mml:msup></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mi>J</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn><mml:mo>,</mml:mo><mml:mn>1</mml:mn><mml:mo>,</mml:mo><mml:mn>2</mml:mn><mml:mo>,</mml:mo><mml:mn>3</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> lines have been
measured to account for the metastable population in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>J</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math> level.

E.  Verdasco

V. Saez Rabanos

A. Gonzalez Ure&#241;a

Reaction Dynamics of Translational
and Electronic Excitation In Ca + SF<sub>6</sub>
Collisions

The evolution since 1982, of far-UV laser photoablation of polymers is described. The experimental data
can be fitted by using a dynamic model which states that the irradiated interface moves at a rate
proportional to the difference between, the intensity reaching it, and the ablation threshold intensity <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>I</mml:mtext><mml:mi>t</mml:mi></mml:msub></mml:mrow></mml:math>.
The screening effect of the ablated gaseous products is taken into account. The experimental etch depth
versus fluence, obtained with our new quartz crystal microbalance technique, can be fitted by adjusting
two parameters of this model; the mean absorption coefficient of the products <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03B2;</mml:mi></mml:math> and the so-called ablation
rate constant k, which is the etch rate for <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mtext>I=I</mml:mtext></mml:mrow><mml:mi>t</mml:mi></mml:msub><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math> MW/cm<sup>2</sup>. These two parameters are wavelength
dependent. The model allows also the calculation of the dose of absorbed energy as a function of depth in
the material. For each layer of the ablated depth, the dose absorbed before and after (reabsorption of the
gas products) ablation are distinguished. The dose of reexcitation varies highly with fluence and the
distribution of gas products broadens accordingly. However, primary products need to be studied. Surface
products are formbd on the final surface, during the postablation phase of the pulsed irradiation. The
probable mechanism of the evolution of excitation energy is discussed, with stress on the elementary steps
leading to heat production.The perspectives of evolution of etching and patterning polymer surfaces by far-UV photoablation are
high in basic research and technology.

Sylvain  Lazare

Vincent  Granier

Ultraviolet Laser Photoablation of Polymers: A Review and Recent Results

The chemiluminescence of BaO in the range 600-800 nm has been observed for the first time in the
reaction between Ba<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mn>6</mml:mn><mml:mtext>s</mml:mtext><mml:mn>6</mml:mn><mml:msup><mml:mtext>p</mml:mtext><mml:mn>1</mml:mn></mml:msup><mml:msub><mml:mi>P</mml:mi><mml:mn>1</mml:mn></mml:msub><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mtext>CO</mml:mtext></mml:mrow><mml:mtext>2</mml:mtext></mml:msub></mml:mrow></mml:math> in a crossed beam experiment under single collision conditions.
The observed spectrum is attributed to the emission from the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>A</mml:mtext><mml:mn>1</mml:mn></mml:msup><mml:msup><mml:mi>&#x03A3;</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:mrow></mml:math> state of BaO and no emission from the
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>A</mml:mtext><mml:mrow><mml:mtext>'1</mml:mtext></mml:mrow></mml:msup><mml:mtext>&#x03A0;</mml:mtext></mml:mrow></mml:math> is visible under our experimental conditions. The distribution of low <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>&#x03BD;</mml:mtext><mml:mo>&#x0027;</mml:mo></mml:msup></mml:mrow></mml:math> in the <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>A</mml:mtext><mml:mn>1</mml:mn></mml:msup><mml:msup><mml:mi>&#x03A3;</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:mrow></mml:math> state appears
statistical at low collision energy and, at higher collision energy, the <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>&#x03BD;</mml:mi><mml:mo>&#x0027;</mml:mo></mml:msup><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math> appears less populated than
statistically predicted. 

J. P. Visticot

P.  Meynadier

J.  Cuvellier

A.  Binet

J. M. Mestdagh

Chemiluminescent Emission in the Reaction <svg style="vertical-align:-3.27605pt" height="19.924999" version="1.1" viewBox="0 0 234.53751 19.924999" width="234.53751" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,15.775)"><path id="x42" d="M372 352v-2q176 -27 176 -159q0 -99 -95 -151q-73 -40 -196 -40h-221v28q65 5 78.5 19t13.5 76v404q0 63 -12 77t-72 18v28h257q102 0 150 -34q26 -18 41 -48.5t15 -65.5q0 -111 -135 -150zM213 362h47q80 0 117.5 32t37.5 96q0 56 -33 92t-100 36q-41 0 -56 -10&#xA;q-13 -8 -13 -50v-196zM213 328v-203q0 -54 17 -72.5t66 -18.5q67 1 110.5 37t43.5 110q0 147 -192 147h-45z" /></g><g transform="matrix(.017,-0,0,-.017,10.194,15.775)"><path id="x61" d="M433 39l-85 -51q-27 0 -47 20q-16 16 -24 44q-5 -3 -24 -16.5t-27 -18.5t-23 -13.5t-25 -12t-19 -3.5q-52 0 -86 36.5t-34 85.5q0 71 81 99q128 43 155 65v17q0 54 -23 83.5t-62 29.5q-28 0 -45 -19t-29 -66q-7 -23 -29 -23q-15 0 -29 13t-14 30t31 40q25 19 68.5 40.5&#xA;t81.5 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The vibrational (and rotational) energy distribution of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mtext>N</mml:mtext><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:msubsup><mml:mtext>(X)</mml:mtext></mml:mrow></mml:math> ions
produced in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>He</mml:mtext></mml:mrow><mml:mo>+</mml:mo></mml:msup><mml:mo>/</mml:mo><mml:msub><mml:mtext>N</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:mtext>O</mml:mtext></mml:mrow></mml:math> charge transfer reaction at thermal
energy has been measured by laser induced fluorescence using
an Ion Cyclotron Resonance cell to store the ions. Vibrational
levels up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>V</mml:mtext><mml:mtext>&#x0022;</mml:mtext></mml:msup><mml:mo>=</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:math> have been observed.The relaxation processes experienced by the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mtext>N</mml:mtext><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:mrow></mml:math> (X) ions before
laser detection are discussed.

j.  Lemaire

R.  Marx

F. Morlet Savary

Laser Induced Fluorescence of <svg style="vertical-align:-3.27605pt" height="18.200001" version="1.1" viewBox="0 0 60.400002 18.200001" width="60.400002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,14.05)"><path id="x4E" d="M719 650v-28q-43 -2 -62 -15t-22 -44q-6 -47 -6 -169v-403h-31l-426 524h-2v-251q0 -111 6 -169q4 -37 24 -50.5t72 -16.5v-28h-237v28q45 2 64.5 16t23.5 49q6 62 6 171v220q0 54 -3 68.5t-17 32.5q-16 19 -34.5 26.5t-54.5 10.5v28h147l418 -502h3v246q0 117 -7 166&#xA;q-4 34 -24.5 47t-73.5 15v28h236z" /></g><g transform="matrix(.012,-0,0,-.012,12.687,5.887)"><path id="x2B" d="M535 230h-212v-233h-58v233h-213v50h213v210h58v-210h212v-50z" /></g><g transform="matrix(.012,-0,0,-.012,12.687,18.138)"><path id="x32" d="M412 140l28 -9q0 -2 -35 -131h-373v23q112 112 161 170q59 70 92 127t33 115q0 63 -31 98t-86 35q-75 0 -137 -93l-22 20l57 81q55 59 135 59q69 0 118.5 -46.5t49.5 -122.5q0 -62 -29.5 -114t-102.5 -130l-141 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Emission properties of <em>s</em>-triazine vapor have been examined for excitation into various vibronic levels of
S<sub>1</sub>. The emission involves broad fluorescence besides the sharp fluorescence emitted from the initially
prepared vibronic level (IPL). At low pressures, the IPL fluorescence exhibits a biexponential decay
composed of fast and slowly decaying portions, and the broad fluorescence also consists of fast and slow
components with lifetimes comparable to those of the IPL fluorescence. The broad fluorescence exhibits
another slow component, which is characterized by a less tendency to undergo collisional quenching. The
emitting levels of the broad fluorescence are regarded as reached directly from the IPL and indirectly via
triplet state. The quantum yield of the slow component of the IPL fluorescence remarkably depends on the
rotational level excited, whereas the quantum yield of the broad fluorescence is nearly independent of the
rotational level excited. These results suggest that K scrambling occurs not only in the intersystem crossing
between singlet and triplet levels but also in the relaxation to other singlet levels from the IPL.

Nobuhiro  Ohta

Effects of Molecular Vibration and
Rotation on Intramolecular Dynamics in S<sub>1</sub> of <em>s</em>-Triazine Vapor

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

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Laser Chemistry