MEASUREMENT OF NEAR-THRESHOLD VIBRATIONAL-EXCITATION OF HCL BY ELECTRON-IMPACT

Relative differential cross sections (sum of 0 and 180-degrees scattering) have been measured for excitation of the vibrational levels of HCl up to upsilon = 5 by impact of electrons at energies from threshold to 3 eV above. Pronounced threshold peaks are observed in the excitation of upsilon = 1 and upsilon = 2, but not for the higher levels. The shapes of the cross sections agree well with the results of several published theoretical studies. The recent unexpected experimental observation of 'boomerang' vibrational structure by Cvejanovic and Jureta in the upsilon = 1 channel has been confirmed.