Absorption Spectra of PbF, PbCl and PbBr

A vibrational analysis has been made of absorption band systems due to PbF, PbCl, and PbBr. A single system of double-headed bands lying between $\ensuremath{\lambda}\ensuremath{\lambda}4100$ and 5300A has been observed for PbF. The separation of the heads is nearly constant. In PbCl a band system with the origin at 4571.8A has been found for each of the isotopes ${\mathrm{Cl}}^{35}$ and ${\mathrm{Cl}}^{37}$. Similarly a system of bands between $\ensuremath{\lambda}\ensuremath{\lambda}4400$ and 5400A has been observed for each of the isotopes ${\mathrm{Br}}^{79}$ and ${\mathrm{Br}}^{81}$. The vibrational analyses are confirmed by the respective isotope shifts. All the bands degrade to the red.