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We present molecular-frame measurements of the recombination dipole matrix element (RDME) in CO2, N2O, and carbonyl sulfide (OCS) molecules using high-harmonic spectroscopy. Both the amplitudes and phases of the RDMEs exhibit clear imprints of a two-center interference minimum, which moves in energy with the molecular alignment angle relative to the laser polarization. We find that whereas the angle dependence of this minimum is consistent with the molecular geometry in CO2 and N2O, it behaves very differently in OCS; in particular, the phase shift which accompanies the two-center minimum changes sign for different alignment angles. Our results suggest that two interfering structural features contribute to the OCS RDME, namely, (i) the geometrical two-center minimum and (ii) a Cooper-like, electronic-structure minimum associated with the sulfur end of the molecule. We compare our results to ab initio calculations using time-dependent density functional theory and present an empirical model that captures both the two-center and the Cooper-like interferences. We also show that the yield from unaligned samples of two-center molecules is, in general, reduced at high photon energies compared to aligned samples, due to the destructive interference between molecules with different alignments. [ABSTRACT FROM AUTHOR]

The first experimental observation of laser induced fluorescence from the furan cation, C4H4O+, is reported. The ion is formed in a supersonic free jet via a two photon ionization involving the 193 nm output of an ArF excimer laser. The B→X electronic transition is probed and vibrational assignments are presented for both states. Comparisons to the infrared, Raman, multiphoton ionization, and photoelectron spectrum of the parent molecule are made. The term value T00 for the B→X electronic transition is located at 24 675 cm-1, which differs drastically with previously reported values from both experimental and theoretical investigations. These differences are discussed and probable explanations proposed. The lifetime of the vibrationless level of the B state is measured to be 330 ns. [ABSTRACT FROM AUTHOR]

Presents a correction to an article on laser induced fluorescence study of the transition of the furan cation in a supersonic free jet expansion, which appeared in the 1987 issue of the 'Journal of Chemical Physics.'