Absorption Band Spectrum of Iodine Monochloride

Abstract

Wave-lengths and series relations in the visible absorption spectrum of ICl.—The visible absorption spectrum of ICl has been photographed and measured. Eight new members have been located in the two series described by Gibson and Ramsperger as corresponding to $n^{\prime \prime }=1\mathrm{}$ and $n^{\prime \prime }=2\mathrm{}$. The limit of convergence of the former series is at $\nu =17430\mathrm{}\pm 5$ ${\mathrm{cm}}^{-1\mathrm{}}$, which makes the heat of dissociation equal to 49650±15 calories per mol. Four members of a new series for which $n^{\prime \prime }=3\mathrm{}$ have been found, so that it has been possible to compute the fundamental vibratory frequency of the molecule as 381.9 ${\mathrm{cm}}^{-1\mathrm{}}$. Still another series of five members is recorded, whose presence may be due to the existence of a close electronic doublet having a separation of about 36 ${\mathrm{cm}}^{-1\mathrm{}}$. The ratio of the two specific heats of gaseous ICl has been calculated to be 1.30 in agreement with empirical results. The fine structure of three consecutive bands has been measured, and the corresponding values of the parabolic parameter $C$ have been computed to be in agreement with the theory of change of moment of inrtia, $I$, with $\omega$, the frequency of vibration of the molecule. By combining both sets of data for band heads and fine structure, the following approximate values for the moment of inertia have been computed: $I^{\prime \prime }=575\mathrm{}\pm 100\times {10}^{-40\mathrm{}}$ g·${\mathrm{cm}}^2$; $I^{\prime }=995\mathrm{}\pm 200\times {10}^{-40\mathrm{}}$ g·${\mathrm{cm}}^2$.