# COLLISIONAL NUCLEAR SPIN INTERCOMBINATION IN $NH_{3}$ OBSERVED IN SUPERSONIC JET EXPANSION BY DIODE LASER SPECTROSCOPY

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 Title: COLLISIONAL NUCLEAR SPIN INTERCOMBINATION IN $NH_{3}$ OBSERVED IN SUPERSONIC JET EXPANSION BY DIODE LASER SPECTROSCOPY Creators: Hepp, M.; Winnewisser, G.; Yamada, Koichi M. T. Issue Date: 1992 Publisher: Ohio State University Abstract: The nuclear spin modifications of molecular wavefunctions are hardly changed in radiactive or collisional processes. In the present study we have found for the lower rotational levels of $NH_{3}$ experimental evidence for the nuclear spin intercombination by collision during the supersonic jet expansion; an over-population in the $(J, K) = (I, l)$ state has been observed in the jet spectra. The populations were determined by measuring the line intensities of the $v_{2}$ band of $NH_{3}$ by a diode laser spectrometer. The rotational temperature reached 9 K for 5 \% $NH_{3}$ seeded in Ar, 16 K for 10 \%, and 53 K for pure $NH_{3}$. The ratio of ortho and para concentration, which is 1:1 in room temperature, was found in the case of 10 \% $NH_{3}$ to be 0.65:1 after the cooling process by supersonic expansion. Description: Author Institution: I. Physikalisches Institut, Universit\""{a}t zu K\""{o}ln URI: http://hdl.handle.net/1811/12684 Other Identifiers: 1992-ME-12