Vincent D. Meyer

Intensity Distribution in the Electron‐Impact Spectrum of Carbon Monoxide at High‐Resolution and Small Scattering Angles

An electron spectrometer, which provides velocity selection before scattering, is described; and the results of a study of relative intensities in the carbon monoxide spectrum are reported. The vibrational levels of the fourth positive band system have been resolved and relative intensities determined for the first nine. The relative intensities are compared with calculated Franck—Condon factors. The agreement is good at low vibrational quantum numbers but noticeable discrepancies are found for high‐vibrational levels.The problem of calculating relative oscillator strengths from a fully resolved spectrum is considered and applied to data obtained in the present research. Relative oscillator strengths are compared with those obtained previously from unresolved spectra.If the Born approximation is valid, then the electron‐impact and ultraviolet absorption spectra should be closely similar. This is actually observed for most of the spectrum but the transition at 12.79 V is an outstanding exception. The relat...

Quadrupole‐Allowed Transitions in the Electron‐Impact Spectrum of N2

The forbidden transitions observed in the nitrogen spectrum below 12.5 V have been studied by electron‐impact methods. Since the theory indicates that electric quadrupole transitions are preferred to singlet—triplet in electron‐impact spectra at intermediate energies, the observed transitions are probably electric quadrupole allowed. This has been demonstrated for the 12.25‐V transition by studying its relative intensity as a function of the scattering angle. The data on the 11.86‐V transition are also compatible with an electric quadrupole transition. In addition, new data on the Lyman—Birge—Hopfield bands in the 60–400‐V energy range indicate that the intensity distribution among vibrational levels is independent of energy.

RELATIVE INTENSITIES OF TWO RYDBERG TRANSITIONS IN THE ELECTRON-IMPACT SPECTRUM OF WATER

The electron‐impact spectrum of water has been determined using a higher‐resolution electron spectrometer. The intensity distribution of five peaks in the spectrum which belong to two different Rydberg transitions has been investigated at zero scattering angle and electron kinetic energy of 200 V. Quantities proportional to the optical oscillator strengths for these excitations have been compared with absorption coefficients from ultraviolet spectra. The entire electron‐impact spectrum in the region below the first ionization potential shows good agreement with ultraviolet absorption.

Vibrational Intensities of the A1Π←X1Σ+ Transition in Carbon Monoxide

The electron‐impact spectrum of carbon monoxide has been investigated at electron energies of 400 and 200 V. The intensity distribution among vibrational levels of the A1Π←X1Σ+ transition has been studied as a function of the scattering angle and electron kinetic energy. The experimental data have been compared with theoretical predictions based on the Born approximation. The results indicate that in the range of the present measurements (θ<6°) the relative intensities are independent of the scattering angle. This observation agrees with the approximate theory of Craggs and Massey. The relative intensities agree fairly well with the Franck—Condon factors calculated by Nicholls except at high vibrational quantum numbers.