Juliet Buttenshaw

Vibration-rotation spectroscopy of the HD+ ion near the dissociation limit

A new method of detecting vibration-rotation transitions in the HD+ ion is described. The technique uses an ion beam and relies upon the detection of infrared photodissociation of levels close to the dissociation limit of HD+. These levels are populated by the electron impact ionization process and measurements of nine rotational components of the v = 18-16 band are described. The results reveal small but systematic discrepancies in the best available theoretical values of the relative energies of these vibration-rotation levels. The resolution of structure arising from proton hyperfine interaction is also described.

The laser magnetic resonance spectrum of the HCO radical at 5.3 μm

Abstract The CO stretching fundamental ν 2 of the HCO radical has been studied using CO laser magnetic resonance. The transitions have been assigned largely on the basis of their Zeeman patterns as low N and K a members of P , Q , and R branches of the a -component (Δ K a = 0) of the hybrid band. No b -type transitions have been detected. Measurements of the resonances have been used to determine the vibrational interval (1868.1714(5) cm −1 ) and the major molecular parameters for HCO in the (0,1,0) level. The changes in values of these parameters from their ground-state values are remarkably small.

The laser magnetic resonance spectrum of the ν2 band of NH2

Abstract The ν 2 fundamental band ( ν 0 = 1497.3 cm −1 ) of the NH 2 radical was studied by CO laser magnetic resonance. The NH 2 radicals were produced by the reaction of hydrated hydrazine and hydrogen atoms obtained from a discharge in water vapor. The assignment was established for about 160 Zeeman resonances which involved levels with 0 ≦ N ≦ 7 and 0 ≦ K a ≦ 5. From an analysis of the observed spectra, combined with the previously reported 10 μm and far infrared LMR spectra, the band origin, the rotational, the centrifugal distortion, and the spin-rotation constants were accurately determined both for the ν 2 = 1 and the ground states. As in the case of HCO, large changes of A , Δ K , ϵ aa , and Δ K s were observed upon the excitation of the ν 2 mode.

Vibration-rotation spectroscopy of the HD+ ion

An approach to the spectroscopy of molecular ions which has obvious appeal is to use the well-established technique of mass spectrometry for producing an appropriate mass-selected ion beam, and to allow the ion beam to interact with electromagnetic radiation. One soon concludes, however, that the direct detection of the absorption of radiation will be difficult, and probably impossible. The reason is that even an intense molecular ion beam (e.g., 1012 ions/sec) has a very low ion density. Consequently, the successful approaches to date have involved indirect detection of absorption spectra; the basic principle is that one attempts to detect the changes in internal state of the ion, brought about by the absorption of radiation, through changes in either the parent ion beam intensity or secondary ion intensities [1]. In the case of the HD+ ion two successful approaches have been described, one involving charge-exchange reaction with H2, the other involving photodissociation. These experiments are described in detail in the third and fourth sections of this review.