The Pure Rotational Spectrum of ICl

Abstract

Frequencies and intensities of a number of lines of the $J=3\mathrm{}\to 4$ rotational transition of ICl were measured and the spectrum analyzed. Constants obtained for IC${\mathrm{l}}^{35}$ are (in megacycles) ${\mathrm{B}}_e=3422.300\mathrm{}$, ${\alpha }_e=16.060\mathrm{}$, $e{q}_{\mathrm{I}}{Q}_{\mathrm{I}}=-2930.0\mathrm{}$, $e{q}_{\mathrm{Cl}}{Q}_{\mathrm{Cl}}=-82.5\mathrm{}$. The mass ratio $\frac{{\mathrm{Cl}}^{35}}{{\mathrm{Cl}}^{37}}$ obtained from this spectrum is 0.9459801, which appears inconsistent with the most recent mass spectroscopic determination. The molecular dipole moment is approximately 0.65 × ${10}^{-18\mathrm{}}$ e.s.u. from intensity measurements.