A new method for observing the rotational spectra of weak molecular complexes: KrHCl

Abstract

A new method of observing the rotational transitions of weak molecular complexes by combining the techniques of microwave Fourier transform spectroscopy, a Fabry–Perot cavity, and a pulsed nozzle source of molecules is described. High resolution and good sensitivity are achieved. Twelve isotopic species of the KrHCl molecule involving all combinations of the 86Kr, 84Kr, 82Kr, H, D, 35Cl, and 37Cl isotopes are assigned and the rotational constants, Cl nuclear quadrupole coupling constants, and centrifugal distortion constants are all given. The molecular structure indicates a linear equilibrium structure with the H(D) atom between the Kr and Cl atoms. However, the inverse moments of inertia measured here indicate large amplitude vibrations of the H(D) atom relative to the Kr–Cl internuclear line. Estimates of the Kr–Cl stretching frequency and force constants, which show considerable dependence on the isotopic species, are also given. Bending frequencies and force constants are also given.

A High-Resolution Microwave Study of the Conformations of Butan-2-ol in a Supersonic Expansion

“…The Fourier transform microwave spectrometer is based on the design of Flygare et al (7,8) and the details have been reported elsewhere (9,10). The main features are described briefly below.…”

Intramolecular hydrogen bonding in chiral alcohols: The microwave spectrum of the chloropropanols

“…Spectra were recorded using a Fourier transform microwave spectrometer, based on the design of Flygare et al [9,10], the details of which have been reported previously [11,12]. The main features of the instrument are described briefly below.…”

Microwave spectrum and molecular structure of the carbon monoxide-hydrogen bromide molecular complex

“…The microwave spectrum of OCHBr was recorded by using the Fabry-Perot Fourier transform spectrometer (5,6,8). The OCHBr dimers were formed by pulsing a mixture of 4% CO and 4% HBr in Ar through a 0.5-mm supersonic nozzle into the cavity.…”

“…A method for the measurement of the molecular properties of transient and other weakly bound molecular species has been developed'by applying Fourier transform techniques in the microwave frequency range (1)(2)(3)(4). The method combines the principles of the pulsed Fourier transform microwave technique, a Fabry-Perot cavity, and synchronization of the microwave pulse with a pulsed supersonic-nozzle beam of a gaseous mixture used to generate, in this case, weak van der Waals molecular complexes (5,6).…”

“…The data were fit by a nonlinear least-squares procedure involving diagonalization of the Hamiltonian matrix. A good fit to the measured transition frequencies was obtained by using the K = 0 symmetric top Hamiltonian, including Br nuclear-quadrupole coupling and the Br spin-rotation interaction, given by X = BOj2 -DJJ4 -Q:VE + ciLJ, 6 _ - [1] where go = 1/2(Bo + Co) is the rotational constant, Dj is the centrifugal distortion constant, c is the Br spin-rotation constant, and I = 3/2 is the Br nuclear spin. Xa, the Br nuclear-quadrupole-coupling constant, is simply related to the matrix elements of the quadrupole Hamiltonian (11), 1-Q:VE, 6 -and is the parameter determined from the fit.…”