The Coriolis Interaction between the v2 = 1 and v3 = 2 States of Nitrosyl Bromide: Anomalous Quadrupole Patterns and Interstate Transitions in the Millimeter-Wave Spectrum.
The millimeter-wave rotational spectra of 79BrNO and 81BrNO in the v2 = 1 and v3 = 2 vibrational states have been reinvestigated. Measurements of the rotational spectrum in the region of maximum c-type Coriolis interaction between the two states allowed the previous analysis to be extended to account for some uncommon effects. For the most perturbed transitions the nuclear quadrupole hyperfine structure arises from coupling of not only the bromine nucleus, but also the nitrogen nucleus with the rotational angular momentum. These effects were satisfactorily fitted with a Hamiltonian describing Coriolis coupling in a molecule with two quadrupolar nuclei. The successful analysis of pure rotational transitions then allowed accurate prediction of rovibrational transitions, six of which were measured for 79BrNO and four for 81BrNO. Copyright 1998 Academic Press.
The rotational spectrum of chlorine nitrate (ClONO2): The ν5/ν6ν9 dyad
Abstract Chlorine nitrate is a molecule of both spectroscopic and atmospheric interest. It is a species whose spectrum in the infrared is marginally resolved in the Doppler limit, thereby limiting the spectroscopic study of its dense rovibrational structure. Analyses of its pure rotational spectrum in the millimeter and submillimeter (mm/submm) spectral regions of the ground, ν 9 , 2 ν 9 , ν 7 , 3 ν 9 , and ν 7 ν 9 vibrational states have been previously reported. In this paper, we report the recording of a new ‘complete’ mm/submm spectrum from 78 to 378 GHz using phase-lock and FASSST (FAst Scan Submillimeter Spectroscopic Technique) systems. We also report the use of these new data for redetermination of spectroscopic constants for the ground state and for an analysis of the ν 5 / ν 6 ν 9 interacting dyad, whose corresponding infrared spectrum lies near 560 cm −1 . The simulation of the rotational structure of ν 5 from the mm/submm analysis is of particular interest because it is one of the bands that is used for atmospheric remote sensing.
Inversion of the Ka = 0 and 1 rotational levels in the lowest excited vibrational state of HNCS☆
Abstract Fairly strong, regularly spaced absorption lines have been observed in the microwave spectrum of HNCS and assigned to b -type, K a = 0 ← 1, Q -branch transitions arising from molecules in the lowest excited vibrational state. The Fortrat diagram of these lines has the appearance of a c -type Q branch, which is impossible in HNCS because of its symmetry. This anomalous b -type Q -branch spectrum is caused by strong a -type Coriolis interactions among the three low-lying bending modes; the K a = 1 levels of the lowest excited vibrational state are perturbed and shifted lower in energy than the K a = 0 levels for each J . This interpretation has been confirmed by the observation of P - and R -branch transitions associated with this Q branch. The band origin has been determined to be −40 104.287 MHz (−1.3377 cm −1 ). The inversion of the K a = 0 and 1 energy levels is consistent with the interpretation of HNCS as a quasi-linear molecule.