Band Spectra of the Two Isotopic Species of Yttrium Monochloride*

Emission spectra of Y35Cl and Y37Cl were photographed in the wavelength region from 6300 to 6930 Å using electrodeless discharge lamps. The molecular constants of the two species of YCl were determined from vibrational analyses of the band systems and rotational analyses of the (0,0), (0,1), and (1,0) bands. The electronic transition to which the bands correspond is of the singlet Σ to singlet Σ type.