Vibrational Autoionization Research Articles

Photoionization of HOF with mass analysis

The ionization yields of HOF+, O+, and OH+ have been studied as a function of wavelength in the photoionization of HOF. The first ionization potential of HOF is 12.71±0.01 eV. The threshold for O+ formation, 14.34 eV, leads to Δ Hf00 (HOF)=−22.8± 1 kcal/mole. The threshold for OH+ formation, 15.07 eV, leads to a value for Δ Hf0 (HOF) in good agreement with the above result if one of two discrepant values for Δ Hf0 (HO+) is chosen. This choice implies that the ionization potential for OH is 12.9o±0.05 eV. The proton affinity of OF is 5.82 eV. Pronounced structure in the ionization yield curves is interpreted as vibrational autoionization in the region near threshold, and as electronic autoionization at higher photon energies.

Photoionization mass spectrometric study of NO. A closer look at the threshold region

The photoionization efficiency curve of NO+ was obtained using the argon continuum in the energy range 9.25–10.00 eV. Considerable fine structure is observed superimposed upon the vibrational steps of the NO+ ionization curve, which is attributed to vibrational autoionization. This structure has been assigned to Rydberg series converging to the excited vibrational levels of the ground NO+ ion (1Σ+).

Angular Distributions of Photoelectrons fromH2: Effects of Rotational Autoionization

Fano's theory of photoabsorption by ${\mathrm{H}}_{2}$ near the ionization threshold is extended to yield photoelectron angular distributions above as well as between the ionization thresholds for alternative rotational states of the ${\mathrm{H}}_{2}^{+}$ ion. In accordance with recent measurements, the angular distribution of direct photoionization is quite different depending on whether or not the ionization is accompanied by a rotational transition. In the autoionization range between rotational thresholds the angular distribution oscillates along each Rydberg line of the rotational autoionization spectrum, resulting in Beutler-Fano resonance profiles which depend strongly on angle of observation. The results are compared with available experimental data. Angular distributions provide very sensitive tests of the theory. The calculation may serve as a basis for extensions to electronic and vibrational autoionization processes.

Mass Spectrometric Studies of Photoionization. IV. Acetylene and Propyne

Photoionization efficiency curves for the parent ions of C 2 H 2 and C 3 H 4 have been measured with a photon bandwidth of 1.3A. For the C 2 H 2 + ion, the minimum onset for ionization of C 2 H 2 occured at 1088 A (11.395±0.015 eV). Vibrational structure and autoionization were observed above the threshold region. For the C 3 H 4 + ion, the minimum onset occured at 1198 A (10.349±0.015 eV), and the second ionization for the C 3 H 4 + ion was observed at 1103 A (11.24 eV). Above the threshold there were observed several vibrational structure and autoionization.