169 research outputs found
Infrared spectra of C2H4 dimer and trimer
Spectra of ethylene dimers and trimers are studied in the nu11 and (for the
dimer) nu9 fundamental band regions of C2H4 (~2990 and 3100 cm-1) using a
tunable optical parametric oscillator source to probe a pulsed supersonic slit
jet expansion. The deuterated trimer has been observed previously, but this
represents the first rotationally resolved spectrum of (C2H4)3. The results
support the previously determined cross-shaped (D2d) dimer and barrel-shaped
(C3h or C3) trimer structures. However, the dimer spectrum in the nu9
fundamental region of C2H4 is apparently very perturbed and a previous
rotational analysis is not well verified.Comment: 21 pages, 4 figure
Three new infrared bands of the He-OCS complex
Three new infrared bands of the weakly-bound He-OCS complex are studied,
using tunable lasers to probe a pulsed supersonic slit jet expansion. They
correspond to the (0400) <-- (0000), (1001)<-- (0000), and (0401) <-- (0000)
transitions of OCS at 2105, 2918, and 2937 cm-1, respectively. The latter band
is about 7900 times weaker than the previously studied OCS nu1 fundamental.
Vibrational shifts relative to the free OCS monomer are found to be additive.
Since carbonyl sulfide has previously been shown to be a valuable probe of
superfluid quantum solvation effects in helium clusters and droplets, the
present results could be useful for future studies of vibrational effects in
such systems.Comment: 16 pages, 1 figure, 4 table
Infrared diode laser spectroscopy of the CCO radical: the 2v1-v1 and v1+v3-v3 difference bands
Sherpa Romeo green journal. Permission to archive final published version. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.The 2n 12n 1 and n 11n 32n 3 difference bands of the CCO radical in the gas phase have been
studied using a tunable infrared diode laser spectrometer. The CCO radical was produced using a
flowing mixture of carbon suboxide and helium subjected to a hollow-cathode discharge. The
spectral region between 1920– 1960 cm21 was probed. Ninety and seventy-five rovibrational
transitions were measured in the 2n 12n 1 and n 11n 32n 3 bands, respectively. The analyses of
these bands yielded spectroscopic constants for the ~001!, ~200!, and ~101! vibrational states. The
band origins for 2n 12n 1 and n 11n 32n 3 were determined to be 1941.85761(54) cm21 and
1936.79402(56) cm21, respectively.Ye
Spectra of the D2O dimer in the O-D fundamental stretch region: the acceptor symmetric stretch fundamental and new combination bands
The O-D stretch fundamental region of the deuterated water dimer, (D2O)2, is
further studied using a pulsed supersonic slit jet and a tunable optical
parametric oscillator infrared source. The previously unobserved acceptor
symmetric O-D stretch fundamental vibration is detected, with Ka = 0 <-- 0 and
1 <-- 0 sub-bands at about 2669 and 2674 cm-1, respectively. Analysis indicates
that the various water dimer tunneling splittings generally decrease in the
excited vibrational state, similar to the three other previously observed O-D
stretch fundamentals. Two new (D2O)2 combination bands are observed, giving
information on intermolecular vibrations in the excited O-D stretch states. The
likely vibrational assignments for these and a previously observed combination
band are discussed.Comment: 23 pages, 5 figures, 2 table
Doped rare gas clusters up to completion of first solvation shell, CO2-(Rg)n, n = 3-17, Rg = Ar, Kr, Xe
Spectra of rare gas atom clusters containing a single carbon dioxide molecule
are observed using a tunable mid-infrared (4.3 micron) source to probe a pulsed
slit jet supersonic expansion. There are relatively few previous detailed
experimental results on such clusters. The assigned clusters include CO2-Arn
with n = 3, 4, 6, 9, 10, 11, 12, 15, and 17, as well as CO2-Krn and -Xen with n
= 3, 4, and 5. Each spectrum has (at least) partially resolved rotational
structure, and each yields precise values for the shift of the CO2 vibrational
frequency (nu3) induced by the nearby rare gas atoms, together with one or more
rotational constants. These results are compared with theoretical predictions.
The more readily assigned CO2-Arn species tend to be those with symmetric
structures, and CO2-Ar17 represents completion of a highly symmetric (D5h)
solvation shell. Those not assigned (e.g. n = 7, 13) are probably also present
in the observed spectra, but with band structures which are not well-resolved
and thus not recognizable. The spectra of CO2-Ar9, -Ar15, and -Ar17 suggest the
presence of sequences involving very low frequency (~2 cm-1) cluster
vibrational modes, an interpretation which should be amenable to theoretical
confirmation (or rejection).Comment: 34 pages, 12 figures, 9 table
Infrared spectra of the water-CO2 complex in the 4.3-3.6 micron region and determination of the ground state tunneling splitting for HDO-CO2
Spectra of water-CO2 dimers are studied using a tunable mid-infrared source
to probe a pulsed slit jet supersonic expansion. H2O-CO2 and D2O-CO2 are
observed in the CO2 nu3 fundamental region (~2350 cm-1), D2O-CO2 is also
observed in the D2O nu3 fundamental region (~2790 cm-1), and HDO-CO2 is
observed in the HDO O-D stretch fundamental region (~2720 cm-1), all for the
first time in these regions. Analysis of the spectra yields excited state
rotational parameters and vibrational shifts. They also yield the first
experimental values of the ground state internal rotation tunneling splittings
for D2O-CO2 (0.003 cm-1) and HDO-CO2 (0.0234 cm-1). The latter value is a
direct determination made possible by the reduced symmetry of HDO-CO2. These
results provide stringent and easily interpreted tests for theoretical water -
CO2 potential energy surface calculations.Comment: 19 pages, 6 figure and 5 table
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