Multichannel quantum theory for propagation of second order transition amplitudes

Formation of NaCl through radiative association: Computations accounting for non-adiabatic dynamics

The radiative association (RA) rate constant is computed for the formation of the diatomic sodium chloride (NaCl) molecule in the temperature interval 1 K-30 K. At these temperatures, RA of NaCl through non-adiabatic dynamics is important. A scattering program has been implemented to carry out calculations of RA cross sections, accounting for coupled dynamics on the lowest ionic and the lowest neutral diabatic ¹Σ⁺ states. The study shows that the non-adiabatic treatment gives a cross section that exceeds that of conventional adiabatic dynamics by one to four orders of magnitude. The contribution to the RA rate constant from Na and Cl approaching each other in the A¹Π state has also been computed using an established quantum mechanical method. Ab initio data from the literature have been used for the potential energy curves, the diabatic coupling, and the electric dipole moments of NaCl.

TWO-PHOTON–INDUCED FLUORESCENCE

Nonresonant two-photon electronic spectroscopy of polyatomic molecules is reviewed for the period since 1979. Emphasis is placed on studies that expose patterns in the two-photon fluorescence (also ionization, optoacoustic) excitation spectra of aromatic hydrocarbons and the effect of vibrations and substitution, particularly within the framework of pseudoparity rules. A section is devoted to biological molecules and the emerging use of two-photon-induced fluorescence anisotropy. Relevant theoretical results are discussed, with emphasis on quantum chemical predictions of vibronic coupling and substituent effects on two-photon absorptivity and tensor properties of individual molecules. This chapter includes higher-order spectroscopy, and a limited number of three- and four-photon studies are discussed.