ABINITIO STUDY OF MULTIPHOTON ABSORPTION PROPERTIES OF FORMALDEHYDE, ACETALDEHYDE, AND ACETONE

The low-lying Rydberg and intravalence excited states of formaldehyde, acetaldehyde, and acetone, accessed by multiphoton absorption, have been investigated at ab initio level according to quantum electrodynamical formalisms, by utilizing random-phase-approximation vertical transition energies and amplitudes. For all three carbonyls, two-photon spectroscopic properties which could be detected with various experimental arrangements have been reported. For formaldehyde, an exhaustive overview on spectroscopic observables associated with multiphoton absorption is presented. The transition probability coefficients and polarization ratios for two-, three-, and four-photon single-color absorption from plane polarized, circularly polarized, and unpolarized light have been evaluated. The molecular response to concerted absorption of two and three photons from two laser beams under various polarization conditions has been investigated as a function of the photon energies. An attempt has also been made to estimate the magnitude and direction of the electrochromic changes in two-photon spectroscopic properties brought about by an external static electric field. © 1990 American Institute of Physics.