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.

Hiroshi  Miyasaka

Hiroshi  Masuhara

Noboru  Mataga

Picosecond 266-<small.letters>nm</small.letters> Multiphoton Laser Photolysis Studies on the Solvated Electron Formation Process in Water and Liquid Alcohols

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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>&#x03C0;</mml:mtext></mml:math> 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.

Katsuhiko  Okuyama

Naohiko  Mikami

Mitsuo  Ito

Internal Rotation of the Methyl
Group in the Electronically
Excited State: <svg style="vertical-align:-0.1638pt" height="7.9499998" version="1.1" viewBox="0 0 8.0749998 7.9499998" width="8.0749998" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,7.675)"><path id="x1D45C" d="M445 282q0 -64 -27.5 -125t-80.5 -104q-80 -65 -168 -65q-73 0 -109.5 46.5t-36.5 116.5q0 92 46.5 163t119.5 104q66 30 108 30q67 0 107.5 -43.5t40.5 -122.5zM355 280q0 62 -26.5 94.5t-64.5 32.5q-26 0 -44 -8q-39 -18 -74 -82t-35 -163q0 -57 25.5 -90.5t70.5 -33.5&#xA;q22 0 36 6q46 20 79 89t33 155z" /></g></svg>- and
<svg style="vertical-align:-0.1638pt" height="7.9499998" version="1.1" viewBox="0 0 13.5375 7.9499998" width="13.5375" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,7.675)"><path id="x1D45A" d="M766 88q-40 -45 -83.5 -72.5t-63.5 -27.5q-39 0 -16 103l49 224q15 68 -10 68q-36 0 -112.5 -78.5t-105.5 -133.5q-27 -101 -38 -165q-35 -4 -77 -18l-6 6q42 153 70 288q12 55 10 78t-19 23q-38 0 -114 -80.5t-101 -131.5q-24 -68 -41 -165q-36 -3 -76 -18l-8 6&#xA;q56 202 87 347q7 33 -3 33q-8 0 -31.5 -17.5t-41.5 -35.5l-12 28q42 45 84 72t63 27q44 0 10 -124l-20 -75h2q92 121 193 178q36 21 64 21q62 0 28 -159l-8 -37h2q50 67 103.5 112t94.5 65q39 19 62 19q60 0 23 -156l-45 -189q-9 -39 2 -39q17 0 71 49z" /></g></svg>-Toluidine

Photodissociation of cadmium diiodide was studied. The nascent vibrational distribution
of CdI(X2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>&#x03A3;</mml:mtext></mml:math>) 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(X2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>&#x03A3;</mml:mtext></mml:math>) 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.

Kazuo  Kasatani

Koji  Mori

Masahiro  Kawasaki

Hiroyasu  Sato

Photodissociation of Cadmium Diiodide

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 &#8220;hot&#8221; 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 (&#102;) of methallyl and allyl radicals were
found to remain about the same for hot and relaxed states. The values (&#102;) in the relaxed
states were determined with errors of &#177;10&#37; to be 0.14 for the methallyl radical, 0.26 for
the allyl radical, and 1.57 &#215; 10&#8722;2 (including the partition function) for the methyl radical.
The molar extinction coefficients of the allylic radicals were 1.4&#8211;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 &#215; 107s&#8722;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.

Nobuaki  Nakashima

Keitaro  Yoshihara

Oscillator Strengths of the Ultraviolet Bands of Hot and Relaxed Methallyl, Allyl, and Methyl Radicals

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.

Yasuki  Endo

Hideto  Kanamori

Eizi  Hirota

Millimeter- and Submillimeter-wave Kinetic Spectroscopy of Reaction Intermediates

Fluorescence decays of jet-cooled pyrazine excited at various positions of rovibronic
transitions within the 0&#8211;0 band were measured by the use of a pulsed dye laser pumped
by an excimer or a nitrogen laser. The experimental data thus obtained on the number
(N) of the triplet states coupled to the initially excited singlet rovibronic state were
analyzed and interpreted by the aid of computer simulation using an asymmetric rotor
program. The results indicate that the extraordinarily great variation of N with excitation
energy and unreasonably small values of N hitherto reported in the literature can be understood
in terms of the conventional theory based on the singlet&#8211;triplet mixed state
model which has been developed for elucidating the mechanism of the occurrence of
dual fluorescence in intermediate case molecules.

Osamu  Sekiguchi

Nobuhiro  Ohta

Hiroaki  Baba

The Mechanism of Occurrence of Dual Fluorescence in Intermediate Case Molecules as Viewed From Rotational Effects

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&#8594;Sn(CH3)3 + CH3 and the other for three-body dissociation,
Sn(CH3)4&#8594;Sn(CH3)2 + 2CH3.

Hisanori  Shinohara

Nobuyuki  Nishi

Photodissociation of Tetramethyltin at 193 <small.letters>nm</small.letters>

The vibrational relaxation mechanism of CH3F whose <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 mode is excited by a transversely
excited atmospheric (TEA)CO2 laser-pulse has been discussed on the basis of
observation of the laser-induced fluorescence (LIF) of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 overtones and of the C&#8211;H
stretching modes and kinetic analyses. The time-evolved LIF in the 3-&#956;m region was
found to be dependent significantly on the laser fluence; at a low fluence (&#60;0.01 J cm&#8722;2),
the emission intensity increased almost exponentially with a rate similar to the one
determined in the experiment with a Q-switched laser, while at a higher fluence
(&#62;0.1 J cm&#8722;2) the emission rose much faster to form a peak which decayed quickly
before a second broad peak appeared. In the wavelength-resolved fluorescence
measurement, it was found that the kinetics of population in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4 level were similar to
those in the 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 level, while those in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>1, 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>5, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>2 + <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>5 and 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>2 levels behaved in a way
different from those in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4 level. These observations lead to the conclusion that the
laser energy poured into the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 mode flows to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4 level directly through 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 as well as
by the successive inter- and intramode V&#8211;V energy transfers, i.e., <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3&#8594;<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>6&#8594;<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>2, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>5&#8594;2(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>2, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>5)&#8594;<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>1&#8594;<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4. A model calculation of the relaxation kinetics, including the
direct V&#8211;V energy transfer between two 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4 levels, could reproduce the 3-&#956;m
emission data. Another significant finding is a non-exponential depopulation in the 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3
level, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>1 and other vibrational levels in the 3-&#956;m region in the final stage of the
relaxation. The deactivation rate is larger for a higher level and is a decreasing function
of time and is much larger than the V&#8211;T/R energy transfer rate. determined in the experiment of weak laser excitation. This may be attributed primarily to the successive
intermode V&#8211;V energy transfers from the 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>4, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>1, 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>5, . . . levels which lie
between the 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 and 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 levels. This process may be repeated if the intramode V&#8211;V
energy transfer from the 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 to the 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 level occurs. The deactivation mechanism found
in this experiment is called &#8216;catastrophic cyclic path&#8217; which is effective until the relative
population distribution in relevant levels between 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 and 3<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math>3 becomes that in equilibrium
at the translational temperature of the CH3F gas.

Hideaki  Nakane

Soji  Tsuchiya

Intra- and Intermode Vibrational
Energy Flow in CH3F Excited by
Irradiation With an Intense CO2
Laser: A Non-Linear Vibrational
Relaxation

The D(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>) ion-pair state of I2 has been analyzed by the optical&#8211;optical double resonance
(OODR) technique. In a stepwise three-photon excitation scheme,
D(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>)&#8211;B3&#928;(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>)&#8211;X1<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mi>g</mml:mi><mml:mtext>+</mml:mtext></mml:msubsup></mml:math>, the D(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>) 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>&#x0394;</mml:mtext></mml:math>J &#61; 0 and &#177;2 for the coherent two-photon transition from the B3&#928;(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>)
state. The D(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>)&#8211;X1<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mi>g</mml:mi><mml:mtext>+</mml:mtext></mml:msubsup></mml:math> fluorescence was resolved to determine the absolute vibrational
numbering of the D(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>u</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>) state. We derived Dunham parameters effective for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math> &#61; 0
through <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>&#x03BD;</mml:mi></mml:math> &#61; 124 which were used to construct a Rydberg&#8211;Klein&#8211;Rees (RKR) potential curve.

Takashi  Ishiwata

Ikuzo  Tanaka

A Spectroscopic Study of the D(<svg style="vertical-align:-3.3907pt" height="18.3375" version="1.1" viewBox="0 0 15.8875 18.3375" width="15.8875" 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="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><g transform="matrix(.012,-0,0,-.012,8.225,5.887)"><path id="x2B" d="M535 230h-212v-233h-58v233h-213v50h213v210h58v-210h212v-50z" /></g><g transform="matrix(.012,-0,0,-.012,8.225,18.138)"><path id="x1D462" d="M515 96q-37 -44 -84.5 -76t-71.5 -32q-12 0 -18 7t-6 34t10 75l19 89h-2q-87 -113 -181 -176q-43 -29 -83 -29q-46 0 -46 63q0 31 9 67l52 222q7 36 -1 36q-10 0 -76 -50l-13 24q47 45 92 71.5t67 26.5q18 0 21 -16.5t-8 -65.5l-56 -242q-16 -67 13 -67q41 0 114 74&#xA;t114 146l32 145l74 26h11q-52 -199 -80 -347q-8 -39 6 -39q7 0 32 17.5t47 39.5z" /></g></svg>) Ion-Pair State of I2 by Optical&#x2013;Optical Double Resonance

The photoionization spectrum of HBr around the first ionization limit was measured at
resolution of up to 5 x 10&#8722;4 nm. The ionizing vacuum ultraviolet radiation was generated
by frequency tripling of the second harmonic output of a dye laser. Three sets of
Rydberg series, each converging to the ground state (2&#928;3/2) of HBr+, were observed on
the longer wavelength side of the ionization limit. By extrapolation of the Rydberg
series, the ionization potential of HBr was determined to be 11.666 &#177; 0.001 eV.

Toshiaki  Munakata

Tadahiko  Mizukuki

Akira  Misu

Motowo  Tsukakoshi

Takahiro  Kasuya

High Resolution Photoionization Spectrum of HB<small.letters>r</small.letters> Measured With Frequency Tripled Laser Radiation

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