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Infrared spectra of the OCS–He van der Waals complex and of OCS–HeN clusters have been studied in the region of the OCS ν1 fundamental band using a tunable diode laser to probe a pulsed supersonic slit jet. For the complex, the spectrum of the normal isotope, 16O12C32S–4He, has been considerably extended and the 34S- and 13C-substituted forms have been recorded for the first time. The data could be analyzed satisfactorily using a conventional asymmetric rotor Hamiltonian with sextic centrifugal distortion terms. For the clusters, the 34S- and 13C-substituted forms have been observed and assigned for N=2–7, including some transitions with higher J values than previously reported for the normal isotope, e.g., R(5). The observed vibrational shifts, relative to the free OCS molecule, were very similar to those of the normal isotope, and most of the difference could be explained by simple scaling. These results constitute a subtle and precise probe of intermolecular forces and dynamical effects in a system which is of current interest for cluster studies. [ABSTRACT FROM AUTHOR]

Abstract: The vibration–torsion–rotation spectrum of CH3SiH3 has been measured from 470 to 725cm−1 at near-Doppler resolution. The full-width at half - maximum of the lines observed near 600cm−1 was 0.0011cm−1. The spectra were obtained using a Bruker IFS 125 HR Fourier transform spectrometer with the broadband source radiation being supplied from the synchrotron emission of the storage ring at the Canadian Light Source. Three vibrational bands were investigated: the lowest lying perpendicular fundamental ν 12 centred near 524cm−1, the lowest lying parallel fundamental ν 5 near 703cm−1, and the torsional hot band ν 12 + ν 6 − ν 6 near 534cm−1. For ν 12 and ν 5, the resolution and sensitivity are much improved over those in earlier studies, with many of the torsional multiplets now being resolved even in the cases where the upper levels are unperturbed. The primary motivation for the present work was the hot band, here reported for the first time, where the dependence of the silyl rock in ν 12 on the torsional motion is much more pronounced. In addition, for the vibrational ground state (gs), two “forbidden” high torsional overtones v 6 =3←0 and 5←0 have been observed that become allowed through resonant mixing of the upper states with ν 12 and ν 5, respectively. In each case, two (K, σ) series have been measured where the mixing is largest. Here σ =0, 1, −1 labels the torsional sub-levels. Using the Fourier transform waveguide spectrometer at E. T. H., the three σ-components of the (J =1←0) transition in ν 12 + ν 6 were observed, and a series of direct l-doubling transitions in ν 12 + ν 6 were measured for σ =0. In a global fit, all the new data have been analysed along with the frequencies for other transitions obtained in earlier investigations. The analysis takes into account the relevant interactions among the torsional stacks of levels in the gs, ν 12, and ν 5. These include the previously known (gs, ν 12) Coriolis-like and (gs, ν 5) Fermi-like interactions along with a higher order (ν 12, ν 5) Coriolis-like coupling introduced here. This last is responsible for the strong perturbation of the ν 5 series with K =10, 11, and 12, and of the corresponding hot band series. A good fit to 9282 frequencies including 7942 new measurements was obtained both with the Free Rotor model in which the torsion is classified as a rotation, and with the High Barrier model in which the torsion is classified as a vibration. The Hamiltonian is discussed with emphasis on the new terms required for treating ν 12 + ν 6 − ν 6. [Copyright &y& Elsevier]

In this work, we present a simple method to spatially encode the transition frequencies of nuclear spin transitions and to read out these frequencies within a single scan. The experiment works by combining pulsed field gradients with an excitation sequence that selectively excites spin transitions within certain sample regions. After the initial excitation, imaging the resulting ẑ-magnetization is used to determine the locations where the excitations occurred, from which the corresponding transition frequencies are determined. Simple experimental demonstrations of this technique on one- and two-spin systems are presented.