Band Spectra of BiBr, BiCl, BiF, and BiI in Absorption

The band spectra of BiBr, BiCl, BiF, and BiI have been examined in absorption and a vibrational analysis made for each of the observed systems. For BiBr there are two systems for each of the isotopes ${\mathrm{Br}}^{70}$ and ${\mathrm{Br}}^{81}$ with origins at 4045.7A and 4869.1A. The lower frequency system degrades to the red, but the direction in which the other degrades is in doubt. In BiCl a band system lying between $\ensuremath{\lambda}\ensuremath{\lambda}3600$ and 4000A has been found for each of the isotopes ${\mathrm{Cl}}^{35}$ and ${\mathrm{Cl}}^{37}$ in addition to the system at $\ensuremath{\lambda}\ensuremath{\lambda}4300$-5500A reported by Saper. The vibrational analyses are confirmed by the respective isotope shifts. One band system between $\ensuremath{\lambda}\ensuremath{\lambda}4150$ and 4900A for BiF and one between $\ensuremath{\lambda}\ensuremath{\lambda}4150$ and 4300A for BiI have been observed and analyzed.