654 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
Electric dipole rovibrational transitions in HD molecule
The rovibrational electric dipole transitions in the ground electronic state
of the HD molecule are studied. A simple, yet rigorous formula is derived for
the transition rates in terms of the electric dipole moment function ,
which is calculated in a wide range of . Our numerical results for
transition rates are in moderate agreement with experiments and previous
calculations, but are at least an order of magnitude more accurate.Comment: 7 pages, 1 figur
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
A molecular superfluid: non-classical rotations in doped para-hydrogen clusters
Clusters of para-hydrogen (pH2) have been predicted to exhibit superfluid
behavior, but direct observation of this phenomenon has been elusive. Combining
experiments and theoretical simulations, we have determined the size evolution
of the superfluid response of pH2 clusters doped with carbon dioxide (CO2).
Reduction of the effective inertia is observed when the dopant is surrounded by
the pH2 solvent. This marks the onset of molecular superfluidity in pH2. The
fractional occupation of solvation rings around CO2 correlates with enhanced
superfluid response for certain cluster sizes
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
Non-Born-Oppenheimer calculations of the lowest vibrational energy of HD including relativistic corrections
In this work we report variational calculations of the two lowest vibrational states of the HD molecule within
the framework that does not assume the Born-Oppenheimer BO approximation. The nonrelativistic energies
of the states were corrected for the relativistic effects of the order of 2 where = 1
c , calculated as expectation
values of the operators representing these effects with the nonrelativistic non-BO wave functions. The non-BO
wave functions were expanded in terms of the one-center explicitly correlated Gaussian functions multiplied by
even powers of the internuclear distance. The v=0→1 transition energy obtained in the calculations is compared
with the previous calculations, as well as with the transition frequency obtained from the experimental
spectra. The comparison shows the need to include corrections higher than second order in to further
improve the agreement between the theory and the experimen
Quark-Lepton Symmetry In Five Dimensions
We construct a complete five dimensional Quark-Lepton symmetric model, with
all fields propagating in the bulk. The extra dimension forms an orbifold with the zero mode fermions corresponding to standard model
quarks localised at one fixed point. Zero modes corresponding to
left(right)-chiral leptons are localised at (near) the other fixed point. This
localisation pattern is motivated by the symmetries of the model. Shifting the
right-handed neutrinos and charged leptons slightly from the fixed point
provides a new mechanism for understanding the absence of relations of the type
or in Quark-Lepton symmetric models. Flavour changing
neutral currents resulting from Kaluza Klein gluon exchange, which typically
arise in the quark sector of split fermion models, are suppressed due to the
localisation of quarks at one point. The separation of quarks and leptons in
the compact extra dimension also acts to suppress the proton decay rate. This
permits the extra dimension to be much larger than that obtained in a previous
construct, with the bound TeV obtained.Comment: 12 pages, references added to match published versio
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