Molecular electronic spectra, dispersion and polarization: The theoretical interpretation and computation of oscillator strengths and intensities

Abstract

HE theoretical computation of absolute transition probabilities for electronic spectra of molecules has been attempted only recently, though T theoretical formulas for relative intensities of lines in a band, and methods for calculating theoretically the relative intensities of bands in a band-system, are well known. The quantum-mechanical calculations on absolute intensities are, for most molecules, necessarily approximate ; their usefulness is still being explored and the methods of computation improved. Fortunately, even very rough theoretical calculations prove to be valuable, since the transition probabilities vary over a range of several powers of ten. The methods of computation, and the results so far achieved in the actual determination of intensities and their interpretation in terms of molecular structure, form the principal subject matter of this Report. Applications to various other molecular properties such as dispersion, polarizability, and the interpretation of molecular refractivities, and to dyes and to the abundance of molecules in astronomical sources, are also discussed.I n the discussion of transition intensities in this Report, we shall consider, for the most part, only absorption spectra, since it is not feasible to obtain extensive experimental data on absolute transition probabilities in emission spectra. 9 2.

Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy

“…where m is the oscillator mass, c is the speed of light, e is the oscillator charge, N is the number density of dipoles, and a S ðuÞ is the absorption coefficient of the intermolecular stretching vibration mode (94). The derived oscillator strength f S , which is proportional to the square of the transition dipole moment, is shown in Fig.…”

Optical spectra of electrons solvated in liquid ethers: temperature effects

“…The previously applied (3) correction for the internal field due to polarization of the solvent molecuies surrounding the absorber (28) is apparently not adequate (27,29,30). Equation 11 is reconimended when an accurate erilpirical equation is not available (30).…”

“…The previously applied (3) correction for the internal field due to polarization of the solvent molecuies surrounding the absorber (28) is apparently not adequate (27,29,30). Equation 11 is reconimended when an accurate erilpirical equation is not available (30). However, values offestimated from [ l l ] may be wrong by 20-30% (29,30), which reduces their usefulness as quantities for conlparison with theoretical calculations.…”

“…Equation 11 is reconimended when an accurate erilpirical equation is not available (30). However, values offestimated from [ l l ] may be wrong by 20-30% (29,30), which reduces their usefulness as quantities for conlparison with theoretical calculations.…”

Reduced-Scaling Coupled-Cluster Theory for Response Properties of Large Molecules

“…Quantum chemical models are now routinely employed to compute absorption properties such as excitation energies [5][6][7][8], oscillator strengths [9,10], and circular dichroism rotational strengths [11][12][13][14][15][16][17], as well as non-absorption properties such as static and frequency-dependent dipole (hyper)polarizabilities and magnetizabilities [18][19][20][21][22][23], and mixed-field perturbations, such as those related to chiroptical response [11,[13][14][15][16][17].…”