Kauffman and Bentley [Laser Chem. 8, 49-59 (1988)] have reported increased laser output by changing
the anion of certain pyridinium oxazole dyes from the tosylate to the mesylate salt. Likewise, zwitterion
variants of these dyes are also reported to have a significantly improved laser output. We find anion
changes to be modest and, with one exception, all zwitterions tested were no better or not as good as the
tosylate salt with respect to lasing output. However, both the mesylate salt and the zwitterion variants
have greatly improved lifetimes if there is no fluorine auxochrome in the basic dye. These authors also
report observation of bifurcated lasing output curves. We see no such phenomena.

R. F. Kubin

R. A. Henry

M. E. Pietrak

D. E. Bliss

J. H. Hall

Anionic and Zwitterionic Photophysical Effects in Some Pyridinium Oxazole Laser Dyes

An effusive thermal molecular beam of CaCI was produced vapourizing a mixture of Ca and CaCI2 within
a crucible with subsequent expansion into vacuum. Lifetimes of <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>CaCl</mml:mtext></mml:mrow><mml:mo>&#x2217;</mml:mo></mml:msup><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>A</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mi>&#x03A0;</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> in its two lowest vibrational
levels were measured under collision-free conditions using laser-induced fluorescence, and values around
33 ns are found; these are discussed with respect to other available data.

E.  Verdasco

V. S&#225;ez Rabanos

H. H. Telle

A. Gonz&#225;Lez Urena

Lifetime Measurements Of <svg style="vertical-align:-2.3205pt" height="18.725" version="1.1" viewBox="0 0 85.449997 18.725" width="85.449997" 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="x43" d="M614 175l29 -10q-33 -109 -57 -154q-121 -26 -184 -26q-90 0 -160.5 29t-112.5 77t-63.5 105.5t-21.5 119.5q0 157 108 253t277 96q36 0 71.5 -5t69 -13.5t36.5 -8.5q15 -102 20 -150l-29 -8q-20 79 -66.5 114t-128.5 35q-119 0 -187.5 -86t-68.5 -207&#xA;q0 -140 73.5 -227.5t188.5 -87.5q73 0 119.5 37.5t86.5 116.5z" /></g><g transform="matrix(.017,-0,0,-.017,11.503,15.775)"><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 29.5q49 0 82 -27q45 -39 45 -123v-185q0 -60 35 -60q18 0 36 11zM275 84v156q-12 -6 -49 -23t-41 -19q-31 -14 -46 -31t-15 -43q0 -35 22.5 -55.5t48.5 -20.5q19 0 42 10.5t38 25.5z" /></g><g transform="matrix(.017,-0,0,-.017,18.965,15.775)"><use xlink:href="#x43"/></g><g transform="matrix(.017,-0,0,-.017,30.354,15.775)"><path id="x6C" d="M238 0h-223v26q48 5 60 17t12 61v473q0 50 -10.5 60.5t-58.5 15.5v24q73 8 148 35v-608q0 -49 11.5 -61t60.5 -17v-26z" /></g><g transform="matrix(.012,-0,0,-.012,34.675,7.613)"><path id="x2217" d="M471 153q-22 -15 -61 -13q-25 31 -45.5 49.5t-56.5 41.5q4 -71 28 -134q-17 -33 -42 -46q-24 12 -42 46q24 63 28 134q-36 -23 -56.5 -41.5t-45.5 -49.5q-36 -2 -61 13q0 28 19 59q65 10 130 43q-65 33 -130 43q-19 31 -19 59q22 15 61 13q25 -31 45.5 -49.5t56.5 -41.5&#xA;q-4 71 -28 134q17 33 42 46q24 -12 42 -46q-24 -63 -28 -134q36 23 56.5 41.5t45.5 49.5q36 2 61 -13q0 -28 -19 -59q-65 -10 -130 -43q65 -33 130 -43q19 -31 19 -59z" /></g><g transform="matrix(.017,-0,0,-.017,42.275,15.775)"><path id="x28" d="M300 -147l-18 -23q-106 71 -159 185.5t-53 254.5v1q0 139 53 252.5t159 186.5l18 -24q-74 -62 -115.5 -173.5t-41.5 -242.5q0 -130 41.5 -242.5t115.5 -174.5z" /></g><g transform="matrix(.017,-0,0,-.017,48.157,15.775)"><path id="x1D434" d="M716 28l-8 -28h-254l8 28q55 5 66 17.5t5 47.5l-30 145h-232l-74 -138q-21 -43 -11 -54.5t72 -17.5l-6 -28h-235l8 28q53 7 73.5 21t53.5 70l319 540l33 8q6 -43 33 -176l80 -381q10 -49 26.5 -63t72.5 -19zM495 281l-49 264h-2l-149 -264h200z" /></g><g transform="matrix(.012,-0,0,-.012,60.625,7.613)"><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 -149h186q42 0 58.5 10.5t38.5 56.5z" /></g><g transform="matrix(.017,-0,0,-.017,66.95,15.775)"><path id="x3A0" d="M703 650v-28q-62 -4 -76.5 -20t-14.5 -76v-402q0 -60 14 -76t74 -20v-28h-266v28q63 4 78 20t15 76v459q0 20 -6 25t-27 5h-249q-23 0 -28.5 -5.5t-5.5 -26.5v-457q0 -60 14 -76t72 -20v-28h-257v28q58 4 72 20.5t14 75.5v402q0 61 -14.5 76.5t-75.5 19.5v28h667z" /></g><g transform="matrix(.017,-0,0,-.017,79.495,15.775)"><path id="x29" d="M275 270q0 -296 -211 -440l-19 23q75 62 116.5 174t41.5 243t-42 243t-116 173l19 24q211 -144 211 -440z" /></g></svg> In A Molecular Beam

The infrared multiple photon trans <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>&#x2192;</mml:mo></mml:math> cis isomerization of crotonitrile was studied over the pressure
range 0.02 torr to 10 torr at fluences of approximately 4J/cm2 using collimated TEA CO2 laser radiation at
942 cm-1. Only minor quantifies of fragmentation products were found at these conditions. At pressures
of 0.1 torr or less, the trans form was completely converted to cis form by about 5000 laser pulses. On
increasing the pressure a collisional regime was entered in which photostationary states were reached with
fewer pulses and having smaller conversions than at low pressure. Both the number of pulses and the
conversion decreased monotonically with increasing pressure. The tactic of driving the reaction in the
exothermic direction gave evidence that the reaction does not occur solely by thermal isomedzation even
in the highly eollisional 10 torr experiments, but that it still has a nonthermal component due to laser
induced isomerization.

Joseph R. Guckert

Robert W. Carr

Thermalization in Infrared Multiple Photon Induced Reactions. The Pressure
Dependence of the Trans <svg style="vertical-align:-0.0pt" height="7.6374998" version="1.1" viewBox="0 0 22.012501 7.6374998" width="22.012501" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,2.9,7.575)"><path id="x2192" d="M901 255q-71 -62 -185 -187l-22 15l102 147h-727v50h727l-102 147l22 15q114 -125 185 -187z" /></g></svg> Cis Isomerization of Crotonitrile

An investigation is presented of the transient vibrational excitation of O3 in the collision dominated
regime initiated by pulsed CO2-laser radiation. IR-UV-double resonance experiments and measurements
of the absorbance for the CO2-laser lines 9P18, 20, and 22 were carried out. Mixtures of O3 (p=17 mbar)
with 02 were investigated at pressures of 160 mbar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>&#x2264;</mml:mo><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:mtext>mixt</mml:mtext></mml:mrow></mml:msub><mml:mo>&#x2264;</mml:mo><mml:mn>1200</mml:mn></mml:mrow></mml:math> mbar and laser fluences of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>0.10</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:mtext>J</mml:mtext><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msup><mml:mo>&#x2264;</mml:mo><mml:msub><mml:mi>F</mml:mi><mml:mrow><mml:mi>i</mml:mi><mml:mi>n</mml:mi></mml:mrow></mml:msub><mml:mo>&#x003C;</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mn>2</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:mtext>J</mml:mtext><mml:mo>/</mml:mo><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math>
. The results are interpreted by numerical simulations in terms of a comprehensive
excitation/relaxation model based upon SSH-theory. Concerning the evolution of the excitation, simulated
transients of the UV-absorbance compare well with the corresponding observed signals. The
saturation of the absorbing O3-transitions is demonstrated by the measured fluence dependence of the
absorption coefficient at the laser wavelengths. The extent of the 03-excitation can be deduced according
to the model from the maximum vibrational temperature Tm reached in the v1- and v3-oscillators. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:mrow></mml:math>
accessible via the UV-transients and also via the absorbed laser energy in the case of slow relaxation at 160
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>160</mml:mn><mml:mtext>&#x200B;</mml:mtext><mml:mtext>mbar</mml:mtext><mml:mo>&#x2264;</mml:mo><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:mi>m</mml:mi><mml:mi>i</mml:mi><mml:mi>x</mml:mi><mml:mi>t</mml:mi></mml:mrow></mml:msub><mml:mo>&#x2264;</mml:mo><mml:mn>340</mml:mn></mml:mrow></mml:math> mbar. In this range both techniques result in the same values for <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:mrow></mml:math>. The experimental
and the corresponding simulated <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:mrow></mml:math> depend exponentially on the laser fluence <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>m</mml:mi></mml:msub><mml:mtext>&#x2009;</mml:mtext><mml:mo>=</mml:mo><mml:mtext>const</mml:mtext><mml:mtext>&#x2009;</mml:mtext><mml:mo>.</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:msubsup><mml:mover accent="true"><mml:mi>F</mml:mi><mml:mo>&#x00AF;</mml:mo></mml:mover><mml:mrow><mml:mi>i</mml:mi><mml:mi>n</mml:mi></mml:mrow><mml:mrow><mml:mn>0.3</mml:mn></mml:mrow></mml:msubsup></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>
provided <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mi>m</mml:mi></mml:msub><mml:mo>&#x003E;</mml:mo><mml:mn>400</mml:mn><mml:mtext>&#x200B;</mml:mtext><mml:mtext>K</mml:mtext></mml:mrow></mml:math> being also confirmed up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:mtext>mixt</mml:mtext></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>1200</mml:mn></mml:mrow></mml:math> mbar by the observed UV-transients.

B.  Raffel

J.  Wolfrum

Pulsed Co2-Laser Excitation of 03/02 Mixtures at Pressures From 0.16 to 1.20 Bar

An anisotropic spatial velocity distribution was observed for NO+ produced following one-color
photolysis/ionization of tert-butyl nitrite (TBN) by a pulsed polarized laser at 266, 355 and 532 nm in a
time-of-flight mass spectrometer. The dependence of the NO+ fragment mass peak profile on the
wavelength and on the polarization was monitored. The most striking feature is the varying fragment peak
splitting obtained under the same experimental conditions by changing the laser polarization direction.
This phenomenon is a result of the vector correlation between the laser polarization,&#202;, at a given wavelength,
the electronic transition dipole moment of TBN,&#956;, and the direction of the NO fragment velocity,
v. The dynamics of the photodissociation process and, in particular, its directional properties are
discussed in view of these results.

P.  Marcus

I.  Platzner

I.  Bar

S.  Rosenwaks

&#202;-&#956;-V Correlation In One-Colour Photolysis/Ionization Of Tert-Butyl Nitrite

The TEA-CO2 laser induced reaction of trans-l,2-dichloroethylene (TDCE) was investigated at 925
cm-1. The laser radiation was focused to yield beam waist fluences of approximately 125 J cm-2. The
major reaction product was cis-1, 2-dichloroethylene (CDCE), with a few per cent of chloroacetylene, and
minor amounts of acetylene, dichloroacetylene, chloroethylene and an unidentified C4 compound also
being formed. The reaction of pure TDCE was studied as a function of number of laser pulses and total
pressure (0.02 to 5 torr). Some experiments were also done with added ethane (20%) and propane (2%).
Evidence was obtained that the formation of the cis isomer occurs via two mechanisms, (1) a unimolecular
isomerization, and (2) a CI atom chain reaction. The results are consistent with laser induced decomposition
of TDCE occurring through the three lowest energy channels: unimolecular structural isomerization
(57.4 kcal/mol); molecular HCI elimination (69 kcal/mol); and C-CI bond scission (89 kcal/mol).

Infrared Laser Photochemistry of Trans-1, 2-Dichloroethylene. Evidence For A CI Atom Chain Reaction

The technique of Multiphoton Induced Chemistry (MPIC) has been employed to initiate ion-molecule
chemistry of organic molecules in solution. We report one of the first examples of the use of liquid phase
multiphoton ionization (MPI) to prepare organic cations, which then react with the solvent in ionmolecule
processes. The products obtained in this chemical sequence are significantly different from those
observed in conventional or multiphoton-induced neutral chemistry in the same solvent. The particular
example explored in this work is the reactivity of the nitrobenzene cation in methanol solvent. Products of
the ion-molecule chemistry, detected by gas chromatography/mass spectrometry, are phenol and benzyl
alcohol. These products depend upon the square of the laser intensity. It is shown by ionization current
measurements in a conductance cell, that ionic species are produced as precursors to the observed
products. The implications of this application of MPI are briefly discussed. A preliminary report on the
unimolecular chemistry of the highly excited neutral molecule is also included. The product of this channel
is nitrosobenzene. It is shown, in this case, that the reactive state is most likely a highly vibrationally
excited ground state molecule, not the lowest triplet level invoked in conventional photochemistry.

Joseph J. Belbruno

Gary  Siuzdak

Simon  North

Uv Multiphoton Induced Chemistry of Nitrobenzene in Solution

The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mn>1</mml:mn></mml:msub><mml:mo>&#x2190;</mml:mo><mml:msub><mml:mtext>S</mml:mtext><mml:mn>0</mml:mn></mml:msub></mml:mrow></mml:math> fluorescence excitation spectra and dispersed fluorescence spectra of jet-cooled (+)-, (-)-
and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mo>&#x00B1;</mml:mo><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>-1-phenylethylamine and their derivatives (amides) have been observed. The 0-0 band of the
amine locates at 37,641 cm-1. The amides which were synthesized from (+)-amine or (-)-amine with
(+)-tartaric acid are diastereomers. It was found that the two diastereomers give the identical spectra with
the 0-0 band at 34,757 cm-1. No difference in the spectrum indicates that the excitation is localized in the
phenyl group which is far from the asymmetric carbon causing diastereoism. It was also found that
1-phenylethylamine has a fast nonradiative relaxation process in the Sstate, but such a process is removed
by the formation of the amide.

Seiji  Yamamoto

Taeko  Niwa

Mitsuo  Ito

Electronic Spectra of 1-Phenylethylamine and its Derivatives in Supersonic Jets

SF6 at pressure of 0.6 Torr in gas mixtures with ozone (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>&#x00F7;</mml:mo></mml:math> 5 Torr) and inert gases: He, Ar, Kr (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>&#x00F7;</mml:mo></mml:math> 5 Torr) was vibrationally excited with and IR pulsed radiation of CO2 TEA laser at 10P20 laser line
(F= 0.6 J/cm2). The vibrational energy transfer from multiphoton excited (MPE) molecules SF6 to the components of gaseous mixture was probed by UV absorption of ozone at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BB;</mml:mi></mml:math> = 253.6 nm band. The relaxation
process of MPE molecules SF6 was proposed to occur through parallel V-V&#39; and V-T collisional channels.
Based on the kinetic model, collisional rate constants were determined from the time evolution of UV
absorption data after laser shot. The obtained values of relaxation rate constants are: <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtable columnalign="left"><mml:mtr><mml:mtd><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mi>V</mml:mi><mml:mo>&#x2212;</mml:mo><mml:mi>V</mml:mi></mml:mrow><mml:mrow><mml:mi>S</mml:mi><mml:msub><mml:mi>F</mml:mi><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2212;</mml:mo><mml:msub><mml:mi>O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>7.7</mml:mn><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>13</mml:mn></mml:mrow></mml:msup><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mtext>cm</mml:mtext><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mtext>s,</mml:mtext><mml:mtext>&#x2009;</mml:mtext><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mtext>V-T</mml:mtext></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mtext>SF</mml:mtext></mml:mrow><mml:mtext>6</mml:mtext></mml:msub><mml:mo>&#x2212;</mml:mo><mml:mtext>He</mml:mtext></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>3.1</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>13</mml:mn></mml:mrow></mml:msup><mml:msup><mml:mtext>cm</mml:mtext><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mi>s</mml:mi><mml:mo>,</mml:mo></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mtext>&#x2009;</mml:mtext><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mi>V</mml:mi><mml:mo>&#x2212;</mml:mo><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>S</mml:mi><mml:msub><mml:mi>F</mml:mi><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2212;</mml:mo><mml:mi>A</mml:mi><mml:mi>r</mml:mi></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>2.3</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>13</mml:mn></mml:mrow></mml:msup><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mtext>cm</mml:mtext><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mi>s</mml:mi><mml:mo>,</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mi>V</mml:mi><mml:mo>&#x2212;</mml:mo><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>S</mml:mi><mml:msub><mml:mi>F</mml:mi><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2212;</mml:mo><mml:mi>K</mml:mi><mml:mi>r</mml:mi></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>7.7</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>14</mml:mn></mml:mrow></mml:msup><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mtext>cm</mml:mtext><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mi>s</mml:mi><mml:mo>,</mml:mo></mml:mtd></mml:mtr><mml:mtr><mml:mtd><mml:mtext>&#x2009;</mml:mtext><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mi>V</mml:mi><mml:mo>&#x2212;</mml:mo><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>S</mml:mi><mml:msub><mml:mi>F</mml:mi><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2212;</mml:mo><mml:mi>S</mml:mi><mml:msub><mml:mi>F</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mo stretchy="false">(</mml:mo><mml:mn>4.8</mml:mn><mml:mo>&#x00F7;</mml:mo><mml:mn>6.4</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>13</mml:mn></mml:mrow></mml:msup><mml:mtext>&#x2009;</mml:mtext><mml:msup><mml:mtext>cm</mml:mtext><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mtext>s</mml:mtext><mml:mtext>.</mml:mtext></mml:mtd></mml:mtr></mml:mtable></mml:math>The observed decay of IR fluorescence from MPE SF6 molecules at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>&#x03BB;</mml:mi><mml:mo>=</mml:mo><mml:mn>6.3</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:mtext>&#x03BC;m</mml:mtext></mml:mrow></mml:math> wave number in SF6-Kr
gas mixtures had an exponential time profile with the constant characteristic relaxation time (V-T). The
rate of IR fluorescence cluenching allowed us to find an effective V-T relaxation rate constants for
collisional partners: <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mtext>V-T</mml:mtext></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mtext>SF</mml:mtext></mml:mrow><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2212;</mml:mo><mml:mtext>Ar</mml:mtext></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>7.8</mml:mn><mml:mtext>&#x200B;</mml:mtext><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>14</mml:mn></mml:mrow></mml:msup><mml:mtext>&#x200B;</mml:mtext><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mtext>s</mml:mtext></mml:mrow></mml:math>. <mml:math display="block" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>K</mml:mi><mml:mrow><mml:mtext>T-V</mml:mtext></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mtext>SF</mml:mtext></mml:mrow><mml:mn>6</mml:mn></mml:msub><mml:mo>&#x2212;</mml:mo><mml:msub><mml:mrow><mml:mtext>SF</mml:mtext></mml:mrow><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:msubsup><mml:mo>=</mml:mo><mml:mn>1.0</mml:mn><mml:mtext>&#x200B;</mml:mtext><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>&#x2212;</mml:mo><mml:mn>12</mml:mn></mml:mrow></mml:msup><mml:mtext>&#x200B;</mml:mtext><mml:msup><mml:mrow><mml:mtext>cm</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:mtext>s</mml:mtext></mml:mrow></mml:math>.

V. V. Timofeev

B. S. Lunin

N. Yu Mordkovich

Yu. N. Zhitnev

Dynamics of Vibrational Relaxation of Multiphoton Excited SF6 Molecules in
Gaseous Mixtures Containing Ozone and Inert Gases (He, Ar, Kr)

We present in this paper a theoretical analysis of the vibrational translational (V-T) relaxation process in
CH3F, carried out by using a numerical model based on rate equations. In particular, we have analysed the
dependence of the V-T relaxation time on the average vibrational energy absorbed per molecule. We
have also investigated the influence of the dependence of the rate constants used in the model, on the gas
translational temperature. The results of the model clearly outline the strongly nonlinear character of the
V-T relaxation process in CH3F, a situation commonly observed in other important polyatomic molecules
of intermediate size each as SF6, freons, and related methylhalides.

V.  Tosa

R.  Bruzzese

C.  de Lisio

S.  Solimeno

Modeling the Vibrational Relaxation of Polyatomic Molecules. The Methylfluoride Case Study

Results are presented of time-resolved absorption investigations of energy transfer processes between a
polymethine dye and an iron complex dye (dye E). For the first time the acceptor molecule transient
absorption depletion generated by energy transfer from an excited donor was observed. The decay time of
the acceptor deactivation <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mo>&#x2248;</mml:mo><mml:mtext>&#x2009;</mml:mtext><mml:mn>140</mml:mn><mml:mtext>&#x2009;</mml:mtext><mml:mtext>Ps</mml:mtext></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> in the presence of the energy donor agrees very well with the S1-state
lifetime of the energy donor.

K. -H. Feller

R.  Gadonas

V.   Krasauskas

Picosecond Absorption Spectroscopy of Energy Transfer Processes in Polymethine Dyes

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