Stephen R . Langhoff

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Full configuraton-interaction (FCI) calculations have given an unambiguous standard by which the accuracy of theoretical approaches of incorporating electron correlation into molecular structure calculations can be judged. In addition, improvements in vectorization of programs, computer technology, and algorithms now permit a systematic study of the(More)
We have observed and assigned a number of far infrared laser magnetic resonance spectra of CH, arising from rotational transitions within the lowest vibrational state of the d ' A , electronic excited state and from transitions between such singlet levels and vibrationally excited levels of the x' 'E , electronic ground state. The singlet-singlet(More)
Thanks to the mid-IR sensitivities of the ISO and IRTS orbiting spectrometers it is now possible to search the diffuse interstellar medium for heretofore inaccessible molecular emission. In view of the recent strong case for the presence of C(7-) (Kirkwood et al. 1998, Tulej et al. 1998),and the fact that carbon chains possess prominent infrared active(More)
Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of 1-methylanthracene, 9-methylanthracene, 9-cyanoanthracene, 2-aminoanthracene, acridine, and their positive ions. The theoretical data are compared with matrix-isolation spectra for these species also reported in this work. The(More)
For the Ca, Sc, Ti and Y atoms calculations performed for the ground states of the neutrals and the ground and several low-lying excited states of the negative ions. Overall the computed electron affinities are in good accord with experiment. The calculations show the rapid stalilization of the 3d orbital relative to the 4p as the nuclear charge(More)
Theoretical studies are reported of the complete dipole excitation and ionization spectrum in H 20 employing Franck-Condon and static-exchange approximations. Large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground-state equilibrium geometry, and previously devised moment-theory(More)
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