Knowledge Bank

The infrared spectra of solid HI and DI as well as mixtures of the two have been reinvestigated in the temperature range $4\circ$ to $78\circ K$. Previously unreported transitions have been found indicating two new regions of thermodynamic stability making a total of five different structures in this temperature range. Marked differences in vibrational spectra in the fundamental region are exhibited. The lowest temperature phase gives a spectrum entirely similar to those of HBr and $HCl1$ in their low-temperature phases. This is consistent with the $observation2$ that the far infrared spectra of HCl, HBr, and HI at $4\circ K$ are analogous and that all three have the same structure at low temperature.