Absorption Band Spectra of Germanous Sulfide: The Isotopic Constitution of Germanium

The absorption spectrum of GeS has been photographed with a 6 foot grating. Two band systems were found in the ultraviolet, the first lying in the region 3358-2709A, the second in the region 2782-2464A. All of the bands are degraded toward the red. The first system consisted of sharp heads, in which the vibrational isotope effect was clearly resolved. Rotational structure could also be observed but only at a considerable distance from the heads. The three abundant isotopes of germanium, 74, 72 and 70, and one of the five less abundant isotopes cited by Aston, 76, were recognized. The vibrational analysis led to the following equation for the bands due to ${\mathrm{Ge}}^{74}$S: - $\nu =32889.5+374.99(v^{\prime }+\frac{1}{2})-1.514\mathrm{}{(v^{\prime }+\frac{1}{2})}^2-575.80(v^{\prime \prime }+\frac{1}{2})+1.80\mathrm{}{(v^{\prime \prime }+\frac{1}{2})}^2.$ The band heads of the second system, for which no isotope analysis was possible because of the low intensity and poor contrast of the bands, can be fitted by the equation: - $\nu =38890.0+310.4(v^{\prime }+\frac{1}{2})-1.35\mathrm{}{(v^{\prime }+\frac{1}{2})}^2-575.8(v^{\prime \prime }+\frac{1}{2})+1.8\mathrm{}{(v^{\prime \prime }+\frac{1}{2})}^2.$ Direct extrapolation of the vibrational constants leads to the following values for the energies of dissociation: for the normal state, common to the two electronic transitions, 5.65 volts and for the two excited states, 2.84 and 2.17 volts respectively. Assuming that the products of dissociation from the normal state are normal atoms, calculation yields for the atomic excitation energy of the dissociation products from the excited state, an average value of 1.27 volts. Both Ge and S have a ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ low-lying, metastable level arising from their basic configurations, the energy values for which are 0.88 volts for Ge and 1.18 volts for S (estimated by McLennan).