A BROADLY TUNABLE, AUTOMATED MICROWAVE SPECTROMETER FOR THE OBSERVATION OF WEAKLY-BOUND COMPLEXES.
Loading...
Date
1989
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
A microwave spectrometer operating from 20.0-60.0 GHz has been constructed for the observation of rotational spectra of weakly bound complexes. The complexes are created in an expansion through a 0.001 ``by 0.06-1.75'' slit nozzle. The microwaves are frequency modulated at 50 kHz and free space propagated across the molecular beam after which they fall on a standard diode detector. Subsequent lock-in detection at twice the modulation frequency is performed to increase the signal-to-noise. A phase-locked, GPIB controllable frequency synthesizer capable of operating at 10.0 MHz-20.0 GHz is used in combination with a doubler or tripler to generate the radiation. The lock-in amplifier is also GPIB controlled so that the entire experiment is computer interfaced. The broadbandedness of the quasi-optical propagation scheme allows for sweeps of up to 20 GHz to be performed without operator intervention. Sweep rates of 200 MHz/hour are achievable with good signal-to-noise for weakly bound complexes. The higher frequency range of this spectrometer relative to currently operating Flygare-Balle type instruments should allow for a number of b-type transitions of near prolate complexes to be observed. Applications of this instrument to new measurements on Ar-HCl, Ar-HCN, $(HCN)_{2}$ and other molecules will be presented.
Description
Author Institution: Division of Geology and Planetary Sciences