Electronic spectrum of the haloacetylenes. Part 1.—Chloroacetylene

The electronic spectra of chloroacetylene and deuterochloroacetylene have been photographed from 3000 to 1000 A. Above 2000 A there are two transitions leading to non-linear excited states. Below 2000 A there is a number of Rydberg transitions all of which are to linear excited states. No Rydberg series have been identified but comparison with the spectrum of acetylene indicates an ionization potential of about 11.4 eV. A number of hot bands involving non-totally symmetric vibrations has been observed indicating that the usual angular momentum selection rules do not hold.