THE EMISSION SPECTRUM OF ALUMINUM MONOCHLORIDE IN THE VACUUM ULTRAVIOLET

Abstract

The spectrum of aluminum monochloride as excited in a high frequency discharge is photographed in the Schumann region using a 1 meter normal incidence grating spectrograph in the first order. Six brief new systems of bands were obtained in the region λλ2075–1820, in addition to three characteristic continua on the longer wavelength side of the discrete systems. The analyses of five of these systems indicate a common lower level which is identified as the ground state of the AlCl molecule. For the remaining system, only the upper state vibrational frequency ω e ′ is derived. All these systems involve six new, hitherto unknown, excited electronic states of the AlCl molecule. The spectrum, when excited in a condensed discharge from a high voltage transformer through steaming AlCl 3 vapor, is found to consist of numerous discrete emission bands in the region λλ2365–2020. These bands are different from those occurring in the high frequency discharge. Because of overcrowding of these bands, owing possibly to lack of adequate dispersion, no analysis is presented.