SUBMILLIMETER-WAVE SPECTRAL-LINES OF NEGATIVE-IONS (SH- AND SD-) IDENTIFIED BY THEIR DOPPLER-SHIFT

For the first time submillimeter-wave transitions of an anion have bee n firmly identified. We observed one transition of SH- (J = 1 <-- 0, 5 64 421.869 MHz) and two of SD- (J = 1 <-- 0, 292 359.129 MHz; J = 2 <- - 584 629.519 MHz) created in the positive column of an electric disch arge set up in a mixture of H2S and argon. By studying the Doppler shi ft brought about by the motion of charged species in the electric fiel d of the discharge we were able to distinguish between positively and negatively charged ions and neutrals. We have hence shown that velocit y modulation techniques commonly used for infrared spectroscopy could also be successfully applied for the study of ions in the submillimete r-wave region. (C) 1998 American Institute of Physics. [S0021-9606(98) 00220-7]