Repetitive Q-modulated HCN gas maser

Abstract

Repetitive modulation of the Q of an HCN gas maser resonator has enabled the effective lifetimes of the rotational levels to be studied as a function of the discharge parameters. Investigation of a Q-modulated maser with pulsed electrical excitation has shown that under certain conditions useful increases in the peak output power at 337 μm can be achieved. The motivation of the investigation is to produce a sub-millimetre radiation source with a high peak power. Such a source will have many future applications in the investigation of phenomena in solid-state and plasma physics. Interest has been confined to a group of maser wavelengths near 337 μm, which are strongly excited when an electrical discharge is run in gases or vapours containing compounds of hydrogen, carbon and nitrogen. The emissions centred at 30 cm-1 have recently been assigned to known vibration-rotation transitions in the HCN molecule by Lide and Maki in 1967. The radiation frequencies calculated from their theoretical assignment are in good agreement with accurate frequency measurements made by Hocker and Javan in 1967. The proposed energy level scheme is also partially confirmed by the observation of competition effects between transitions which are reported here. These effects have also been observed by Hocker and Javan. Further details concerning spectroscopic measurements are given in the paper by Matthias et al. in 1968. The results of two experiments are reported. Firstly, certain conditions necessary for the emission of the radiations at 310 μm, 311 μm, 337 μm and 373 μm are discussed. Secondly, experiments in which there is Q modulation of the rotational levels are described.