Spectroscopic and dynamical studies of the van der Waals complexes of benzene&#8211;Ar, benzene&#8211;N2 and benzene dimer in the electronically ground state (S0) have been performed by the use of stimulated Raman&#8211;UV optical double resonance spectroscopy. The vibrational frequency of mode 1 of the complexes and the decay rate constants of the 11 levels (&#8764;993 cm&#45;1) have been measured. The vibrational frequency
shifts of mode 1 in S0 upon complex formation were less than 1 cm&#45;1for all the complexes. On the
other hand, the decay rate constant due to intramolecular vibrational redistribution and/or vibrational
predissociation showed a drastic change. The decay rate constant of the 11 level of the benzene dimer
was 2.4 &#215; 107 s&#45;1, while those of the benzene&#8211;Ar and benzene&#8211;N2 complexes were much smaller than 1 &#215; 106 s&#45;1. It was also found that the decay rate constant in S0 is much smaller than that in S1. For the
benzene dimer, the depolarization ratio of Raman band of mode 1 was recalculated by taking into account
of the anisotropy of the polarizability of benzene molecule. The comparison between the observed and
calculated polarization ratio shows that the benzene dimer has the &#8220;T-shaped&#8221; structure which was
proposed by the group of Felker.

Takayuki  Ebata

Seiichi  Ishikawa

Mitsuo  Ito

Shi-Aki  Hyodo

Stimulated Raman&#8211;UV Optical Double Resonance Spectroscopy of Van Der Waals Complexes of Benzene

We report the results of rotational coherence spectroscopy on tolane, tolane&#8211;Ar, and tolane&#8211;N2. The
results on tolane are consistent with a planar geometry for the species. They also provide information
about the symmetries of excited vibronic states in the species. The results on the van der Waals complexes
provide significant experimental constraints on where the small species bind to tolane. In addition, we
report the observation of a rapid excited-state decay process in the complexes and discuss the possible
nature of this process.

Shane M. Ohline

Joann  Romascan

Peter M. Felker

Rotational Coherence Spectroscopy and Excited-State Dynamics of Tolane and its Van Der Waals Complexes with Argon and Nitrogen

The &#195;1Au &#8592; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mtext>X</mml:mtext><mml:mo>&#x02DC;</mml:mo></mml:mover></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msubsup><mml:mo>&#x2211;</mml:mo><mml:mi>g</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>
 electronic transition of the vibrationally excited acetylene molecule was studied by
IR&#8211;UV double resonance spectroscopy in gas and in a supersonic jet. The C&#8211;H antisymmetric stretching
vibration <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>ant in the &#195; state was clearly observed when the molecule was excited to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>sym &#43; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>ant
combination vibration in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mtext>X</mml:mtext><mml:mo>&#x02DC;</mml:mo></mml:mover></mml:math> state by the IR laser. When the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>ant fundamental vibration was excited,
the C&#8211;H in-plane cis-bending vibration &#957;cis(in) in the &#195; state was observed strongly, while <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>ant almost
disappeared. The difference was interpreted in terms of Fermi resonance of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>ant fundamental vibration
in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mtext>X</mml:mtext><mml:mo>&#x02DC;</mml:mo></mml:mover></mml:math>. The predissociation threshold was newly determined to be 46,439&#764;46,673 cm&#45;1 (133.11 &#177; 0.33 kcal/mol). In the region above the predissociation threshold, strong vibrational mixing was found. The
higher members of the progression of the trans-bending vibration starting from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03BD;</mml:mi><mml:mrow><mml:mtext>CH</mml:mtext></mml:mrow></mml:msub></mml:math>ant were assigned. It
was suggested that the nonradiative relaxation accelerated in the region above 51,744 cm&#45;1.

Masaaki  Fujii

Shigeki  Tanabe

Yasuo  Okuzawa

IR-UV Double Resonance Spectrum of Acetylene Below and Above the Predissociation Threshold

High resolution photoelectron spectra are reported for styrene and stilbene with an emphasis on identifying
the low frequency modes which are important in the phenyl&#8211;vinyl torsional motion. In the styrene
cation three low frequency out-of-plane vibrations are measured, &#957;42, &#957;41 and &#957;40 as well as a number
of higher frequency in plane modes. Generally the low frequency modes do not appear with significant
intensity but by pumping the appropriate modes in the S1 intermediate state the intensity for these modes
in the threshold ionization spectrum is quite good. In the stilbene cation the analogous phenyl&#8211;vinyl
torsion, &#957;37, is also measured as well as the related mode &#957;36. The ethylene torsional mode in stilbene
is not observed. In both molecules the observed frequencies are used to relate the electronic structure
of the cation to the S1 and S0 states of the molecule.

Jonathan M. Smith

J. L. Knee

Threshold Ionization Spectroscopy of the Low Frequency Vibrational Modes of Styrene and Trans-Stilbene Cations

The spectroscopic properties of mercury and mercury dimer clustered with water, ammonia and 1&#8211;1
dimethylether have been studied through mass selected resonance enhanced multiphoton ionization
spectroscopy. The ground state structure of these clusters have been calculated. Comparison between
calculations and experimental results show that the spectrum is not governed by the structural properties
of the clusters.

C.  Dedonder-Lardeux

S.  Martrenchard-Barra

C.  Jouvet

D.  Solgadi

F.  Amar

Evolution of the Spectroscopic Properties of Hg and Hg2 Interacting with Molecular Clusters

The fluorescence/phosphorescence excitation spectra, the dispersed fluorescence/phosphorescence spectra
and the sensitized phosphorescence excitation spectrum have been measured for jet-cooled p-benzoquinone.
The assignments of vibronic bands in the 1B1g(n&#45;,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>&#x03C0;</mml:mi><mml:mo>&#x2217;</mml:mo></mml:msup></mml:math>) &#8592; 1Ag and 1Au(n&#43;,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>&#x03C0;</mml:mi><mml:mo>&#x2217;</mml:mo></mml:msup></mml:math>) &#8592; 1Ag transitions
have been definitely established. The phosphorescence spectra from vibronic levels of 3Au exhibit a
feature of single vibronic level emission. The 3Au &#8592; 1Ag transition was also vibrationally analyzed.

Isamu  Suzuka

Masaomi  Sanekata

Nobuhiro  Ohta

Singlet And Triplet n,<svg style="vertical-align:-0.1638pt" height="13.95" version="1.1" viewBox="0 0 17.775 13.95" width="17.775" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,13.688)"><path id="x1D70B" d="M574 449q-23 -58 -38 -79q-16 -4 -79 -4q-27 -100 -46 -219q-14 -87 7 -87t74 36l13 -27q-74 -81 -139 -81q-48 0 -48 62q0 22 8 59l60 258l-154 4q-21 -103 -54.5 -209t-64.5 -151q-38 -23 -83 -23l-7 15q46 36 94 152.5t64 216.5q-81 0 -138 -54l-18 23q22 27 39.5 43&#xA;t61.5 33.5t100 17.5q43 0 131.5 -2.5t129.5 -2.5q23 0 33.5 5t24.5 25z" /></g><g transform="matrix(.012,-0,0,-.012,10.113,5.525)"><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></svg> Transitions of Jet-Cooled p-Benzoquinone

Three types of analyses: generalized conventional spectroscopic analysis, statistical analysis, and hierarchical
analysis, by which we aim to extract dynamical information from the complex spectrum of small
polyatomic molecules are reviewed by referring to recent studies on vibrationally highly excited acetylene.
A convolution analysis, one type of hierarchical analysis, is performed on the dispersed fluorescence
spectrum of acetylene to demonstrate its practical applicability. Based on previous studies, as well as
on the convolution analysis, a systematic and efficient procedure to treat such complex spectra is
discussed.

Kaoru  Yamanouchi

Jun  Miyawaki

Soji  Tsuchiya

David M. Jonas

Robert W. Field

New Scheme for Extracting Molecular Dynamics from Spectra: Case Study on Vibrationally Highly Excited Acetylene

Extreme ultraviolet-visible double resonance excitation has been employed to populate selected rovibronic
levels of the EF <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mi>g</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>, H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mi>g</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:math>, I <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msub><mml:mtext>&#x03A0;</mml:mtext><mml:mtext>g</mml:mtext></mml:msub></mml:math> and J <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msub><mml:mtext>&#x0394;</mml:mtext><mml:mtext>g</mml:mtext></mml:msub></mml:math> states of H2 lying in the range between 115,000 and
117,600 cm&#45;1 above the ground state X <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mtext>g</mml:mtext><mml:mo>+</mml:mo></mml:msubsup></mml:math>. Tunable coherent extreme ultraviolet radiation, generated
by a four-wave mixing process in Xe, prepares H2 in the intermediate B <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mtext>u</mml:mtext><mml:mo>+</mml:mo></mml:msubsup></mml:math> (v &#61; 6, J) state. Subsequent absorption of the visible laser radiation brings H2 to the higher gerade states and the fluorescence light
from these states is detected. Term values of 41 rovibronic levels in these gerade states, including 23
previously unidentified levels, were determined. The single rovibronic fluorescence lifetimes were also
measured under the collision-free condition. The fluorescence lifetimes of the EF <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi></mml:mi><mml:mn>1</mml:mn></mml:msup><mml:msubsup><mml:mtext>&#x03A3;</mml:mtext><mml:mtext>g</mml:mtext><mml:mo>+</mml:mo></mml:msubsup></mml:math> states exhibited
significant rotational dependences. The nonadiabatic coupling among the adiabatic upper gerade vibronic
states explained the observed rotational dependences successfully.

Juntarou  Ishii

Koichi  Tsukiyama

Kiyoji  Uehara

Identification of Excited Gerade States of Molecular Hydrogen with Extreme Ultraviolet-Visible Double Resonance Excitation Technique

The SEP&#8211;LIF (stimulated emission pumping-laser induced fluorescence) technique was applied to the
investigation of dynamical behavior of vibrationally excited phenol and anisole produced in the supersonic
expansion. In the SEP&#8211;LIF scheme, a molecule excited to a specific vibrational state by SEP is detected
by measuring the LIF excitation spectrum with an appropriate delay to probe the vibrational relaxation.
Four vibrational states, 6a1, 16a2, 121 and 11, of phenol, and six vibrational states, 18b1, 18b2, 6a1, 121,
16a2 and 11, of anisole were investigated. For both of phenol and anisole, it is found that the relaxation
of the vibrational states below 1,000 cm&#45;1 in the ground electronic state is so slow under the collisionless
condition that only the transitions from the vibrational states initially prepared by SEP are observed as
the SEP-induced bands in the SEP&#8211;LIF spectra. The low frequency torsional motion of methyl group in
anisole does not accelerate IVR (intramolecular vibrational redistribution) much in this energy region.

Masao  Takayanagi

Ichiro  Hanazaki

Stimulated-Emission-Pumping Laser-Induced-Fluorescence Spectroscopy of Phenol and Anisole

Absorption spectra are detected for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>C</mml:mtext><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>&#x2212;</mml:mo></mml:msubsup></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>C</mml:mtext><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>2&#x2212;</mml:mo></mml:msubsup></mml:math> produced electrolytically in solution at room temperature.
Theoretical analysis of the spectrum of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>C</mml:mtext><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>&#x2212;</mml:mo></mml:msubsup></mml:math> by CNDO/S calculations gives an interpretation of the characteristic
near-IR bands, the weak visible bands, and the strong bands in the UV region. The emission
spectrum of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>C</mml:mtext><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>&#x2212;</mml:mo></mml:msubsup></mml:math> is a mirror image of the near-IR absorption band, and the detection of the emission
reconfirms our original assignment of the absorption spectrum. The nature of the spectrum of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>C</mml:mtext><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>2&#x2212;</mml:mo></mml:msubsup></mml:math> is
characterized by a similar orbital picture to that of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mtext>C</mml:mtext><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>&#x2212;</mml:mo></mml:msubsup></mml:math>. Further laser experiments of significance are
proposed.

Tatsuhisa  Kato

Absorption and Emission Spectra for C60 Anions

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