[en] This book reveals the interrelationships between apparently unrelated observables, electronic states, and molecules. This book emphasizes: introduction to the theory of rotating-vibrating diatomic molecules with nonzero spin and orbital angular momenta; simplification and calculation of matrix elements of all of the important terms in the molecular Hamiltonian; methods for reduction of the exact Hamiltonian to molecular fit-parameters; sizes of and relationships among molecular constants and perturbation parameters; and specific examples: intensity effects, predissociation, and autoionization

No abstract available

[en] In molecular photoionization, many shape resonances have been observed these last years. They appeared mainly in non-hydride molecules built on atoms of the first or second rows of the periodic table. These resonances have been called molecular shape resonances. Another class of shape resonances, named atomic-like shape resonances, is expected in heavy hydrides composed of atoms for which giant shape resonances have been observed in their 4d inner shell photoionization spectra for example Xe, Ba and Eu³. A preliminary calculation of the 4d inner shell photoionization of HI has been made recently and gives a first theoretical example of such atomic like shape resonances. A question could be asked: are these two different types of shape resonances in molecules comparable to giant resonances in atoms? In this paper, the author tries to give an answer to this question. 16 references, 2 figures, 2 tables

[en] Most of the rules for atomic or molecular autoionization have been derived within a two-channel model, involving one open channel (the continuum) and one closed channel (the discrete states). Very often, especially in molecules, autoionization processes involve additional coupled channels, open or closed, which complicate the resonance features by violating the two-channel rules. As an example the authors discuss the case of complex resonances, due to the autoionization of a Rydberg series close to its ionization threshold, perturbed by an isolated discrete state. 14 references, 5 figures

No abstract available

[en] The high resolution relative photoionization cross section for HCl is reported in the wavelength region 720--975 A. In addition, results of calculations are presented for spin--orbit autoionization in the energy region between the X ²Pi/sub 3/2/ and X ²Pi/sub 1/2/ ionization thresholds and for electrostatic autoionization in the energy region containing Rydberg series converging to the A ²Σ⁺ excited ionic state. For the case of spin--orbit autoionization in the region just above the X ²Pi/sub 3/2/ ionic threshold, it is found that the energy positions of the first peaks are approximately correct if the ionization potential is modified by ≅80 cm^-1; however the intensities of the peaks are strongly perturbed, most probably by high lying vibrational levels of the V ¹Σ⁺ valence state. In the wavelength region 780--930 A, two progressions of Rydberg states converging to the A ²Σ⁺ excited ionic state and autoionized by electrostatic interaction are also studied by ab initio multichannel quantum defect theory. Qualitative agreement with the experimental data is obtained by a slight adjustment of some quantum defects, the other parameters being those obtained by ab initio calculations. Comparison with the absorption spectra of both HCl and DCl is also made. Progression I of Terwilliger and Smith [J. Chem. Phys

[en] The high resolution relative photoionization cross section for HBr is reported in the energy region between the ²Pi₃/sub //₂ and ²Pi₁/sub //₂ ionic limits. A theoretical interpretation of the spectrum is given using the multichannel quantum defect theory with an ab initio calculation of the relevant electronic quantities. The vibrational couplings due to the R variation of both the electrostatic and the spin-orbit matrix elements are introduced and are shown to be essential to reproduce the qualitative features of the experimental data in the 1052--1060 A wavelength region

[en] The rotational structure associated with the X ²Π_g (000) ground ionic state of CO⁺₂ has been investigated by threshold photoelectron spectroscopy and semiempirical calculations based on the distribution of Rydberg state levels at n=2000. The calculations are in very good agreement with the rotationally resolved spectra for the X ²Π_g,3/2 and X ²Π_g,1/2 spin--orbit levels for both room temperature and supersonically cooled ground state CO₂. Intensity anomalies are partly explained by decay mechanisms involving rotational and spin--orbit autoionization. copyright 1995 American Institute of Physics

[en] With the goal to interpret the experimental results obtained quite recently by Heays et al. [J. Chem. Phys. 141, 144311 (2014)] on the predissociation of the Rydberg W ¹Π (v = 1) vibrational level of the CO molecule, we report herein ab initio potential energy curves of some of its valence and Rydberg states of both ¹Π and ³Π symmetry. Our results confirm that the above vibrational level is perturbed by a new electronic ¹Π state not observed until now. They correctly reproduce the linewidths of predissociation of the two interacting levels.

[en] Full text: Molecular nitrogen is a major absorber of extreme ultraviolet (XUV) solar radiation in the Earth's atmosphere, and is associated with 1Σ_u + and ¹π_u states which undergo strong predissociation via ³π_u states. Knowledge of the spectroscopy and dissociation dynamics of N₂ are also vital to analyse data from, e g., the current encounter of Cassini with Titan We have determined new N₂ isotopic lifetimes via ultrahigh resolution XUV + UV laser ionization (resolving power 10⁷). The lifetimes depend strongly on the vibrational level and the isotope. A coupled Schrodinger equation model for the linewidths reveals new information about the predissocation processes that determine these lifetimes. Copyright (2005) Australian Institute of Physics