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  • 1
    Electronic Resource
    Electronic Resource
    Unstable intermediates. 4. Thioformaldehyde (1976)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 98 (1976), S. 6054-6055 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00435a055
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  • 2
    Electronic Resource
    Electronic Resource
    Unstable intermediates. 5. Thioketene (1977)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 99 (1977), S. 1663-1664 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00447a073
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  • 3
    Electronic Resource
    Electronic Resource
    Weakly bound NeHF (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 711-721 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used ab initio methods to characterize the Ne–HF van der Waals complex. The interaction energy was determined using size consistent, correlated CEPA wave functions expanded in a Gaussian basis chosen to represent both intraatomic effects and the low order multipole moments and polarizabilities of Ne and HF. The calculated well depths are −65 cm−1 for linear Ne–HF and −39 cm−1 for linear Ne–FH, with an intervening saddle point at −27 cm−1. The induction contribution to the energy is significantly greater for Ne–HF than for Ne–FH, but dispersion remains the dominant attraction over the region of interest. Converged variational and close-coupling calculations using the ab initio potential surface reveal three bound levels of the Ne–HF stretch mode, and several metastable levels correlating asymptotically with rotationally excited HF( j=1). Though nearly degenerate, the lifetimes of the two metastable Π (body frame Λ=±1) bending levels differ markedly because of different rotational coupling strengths to the Σ (body frame Λ=0) bending state, which undergoes rapid rotational predissociation. From the calculated line positions, widths, and intensities we have synthesized far infrared and infrared spectra of Ne–HF and Ne–DF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457177
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  • 4
    Electronic Resource
    Electronic Resource
    The ultraviolet absorption spectrum of the A˜ 1A‘2←X˜ 1A1 transition of jet-cooled ammonia (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6669-6676 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The A˜←X˜ absorption spectra of NH3 and ND3, recorded in a cold molecular jet, are presented. Vibrational band progressions resolvable up to v'2=14 appear. No other vibrations are present, either alone or in combinations. Relative band intensities for v2 progressions are recorded, and the homogeneous lifetime broadenings of vibrational levels of the A˜ state are reported. The FWHM linewidths span 34–293 cm−1 over all bands of NH3 and 30–135 cm−1 over the v'2=2 through 14 bands of ND3. In general, the rate of dissociation increases nonlinearly with vibrational energy. The band intensity alternation, previously observed only in matrix spectra below 15 K, has been observed in these very cold gas phase samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452415
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical A 1A‘2–X 1A1 absorption and emission spectrum of ammonia (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6677-6692 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential energy, electric dipole moment, and electronic transition moment surfaces have been calculated for the A and X states of NH3 from CASSCF and CEPA electronic wave functions. Anharmonic vibrational term values, Franck–Condon factors, and A–X radiative transition probabilities for the symmetric stretching and bending modes of NH3 and ND3 have been evaluated. The theoretical absorption spectra at room and low temperatures agree well with experimental data. The symmetric stretching mode in the A state has only small intensities in the A–X absorption spectrum. Emission rates from various initial vibronic levels of the A state are given. The ab initio electric dipole moment surfaces for the ground state of NH3 have been used to compute transition moments, which are in good agreement with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452416
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  • 6
    Electronic Resource
    Electronic Resource
    Dissociation of NH3 to NH2+H (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6693-6700 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential energy, dipole moment, and electronic transition moment surfaces for the lowest dissociative pathways of the singlet X˜ and A˜ states of NH3 yielding NH2 (X˜ 2B1,A˜ 2A1) +H(2S) products have been calculated using complete active space MCSCF ab initio wave functions. The A˜ state dissociation proceeds via a minimum barrier at the following planar geometry: αHNH =113°, rNH =1.042 A(ring) (in the NH2 fragment), and RNH =1.323 A(ring) (in the dissociation coordinate). The barrier height is calculated to be 3226 cm−1 with an expected accuracy of about 300 cm−1. The barrier height increases with increasing out-of-plane angle. Close to the barrier there are strong variations of the shapes of the dipole moment and transition moment surfaces. The minimum energy path through the X˜–A˜ conical intersection follows planar geometries. Along this pathway the angle αHNH decreases, but the distance rNH in the NH2 fragment hardly changes. The crossing distance RcNH of the X˜ and A˜ states in planar structures depends strongly on αHNH and varies from about 1.68 A(ring) (60°) to infinity (180°). The photodissociation process NH3(A˜) →NH2(X˜ 2B1) +H(2S) is discussed on the basis of the calculated potential energy surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452417
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  • 7
    Electronic Resource
    Electronic Resource
    A theoretical rotationally resolved infrared spectrum for H2O+ (X 2B1) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2818-2833 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Three-dimensional potential energy and electric dipole moment functions for the electronic ground state of H2O+ have been calculated from highly correlated multiconfiguration reference configuration interaction (MRCI) electronic wave functions. The analytic representations of these functions have been used in vibrational and perturbational calculations of the rovibrational absorption spectrum of H2O+. The quartic force fields in normal coordinates have been employed in the evaluation of the equilibrium spectroscopic constants in H2O+, D2O+, and HDO+ by perturbation theory. The equilibrium structure, vibrational band origins, centrifugal distortion constants and rotational energy levels agree very well with the available experimental data. Absolute vibrational band intensities have been calculated from the dipole moment functions and are compared with theoretical integrated band intensities. The radiative lifetimes of excited vibrational states exhibit mode specific variations. The rotationally resolved room temperature absorption spectra have been evaluated ab initio for the pure rotational and the ν2, 2ν2, ν1, ν3, and 3ν2 transitions. The rovibrational electric dipole transition matrix elements and absolute line intensities are given for the most intense transitions. These data take full account of anharmonicity effects and vibration–rotation coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456951
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  • 8
    Electronic Resource
    Electronic Resource
    Ab initio calculations of the vibration–rotation spectrum of HCS− (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2641-2651 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The three dimensional near equilibrium potential energy and dipole moment surfaces of the electronic ground state of HCS− have been calculated from correlated MCSCF-CI electronic wave functions. These data have been used in perturbation and variational calculations of the bound and electron detachment anharmonic vibration–rotation levels. The electron affinity EA0 is calculated to be 0.41 eV and the equilibrium geometry to be RCH=1.111 A(ring), RCS=1.687 A(ring), α=106°. The fundamental vibrational band origins and integrated absorption band intensities are predicted to be 2648 cm−1/1318 cm−2 atm−1 (CH stretch), 1140 cm−1/145 cm−2 atm−1 (bend), and 911 cm−1/50 cm−2 atm−1 (CS stretch) in HCS−. The components of the dipole moment functions are given analytically. The dipole moment in the vibrational ground state of HCS− has been calculated to be 2.122 D. Radiative transition probabilities among low lying vibrational levels have also been evaluated. It is found that the radiative lifetimes vary in a mode-specific way. The theoretical photoelectron spectrum of HCS− and DCS− is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454044
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  • 9
    Electronic Resource
    Electronic Resource
    The radiative lifetime of A 1Πu C2 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2847-2853 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This note reports ab initio potential curves of A 1Πu and X 1Σ+g states of C2, and the A–X radiative lifetimes. The calculations are based upon configuration interaction wave functions formed from single and double electron excitations from state-averaged MC-SCF reference functions expanded in a Gaussian basis. The lifetimes for (J′=1,v′) A 1Πu are calculated to be about 25% longer than those found in previous ab initio works, but about 25% shorter than the most recent LIF measurements of Bauer, Becker, Bielefeld, and Meuser. Also reported are the quadrupole moments of the A 1Πu and X 1Σ+g states as a function of internuclear distance and the quadrupole lifetimes of several (v′=0,J′) levels in the X state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453072
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  • 10
    Electronic Resource
    Electronic Resource
    Ab initio calculation of potential energy surfaces and spectroscopic properties of H2S and H3S+ (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5107-5116 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Potential energy surfaces and spectroscopic properties were calculated for H2S and H3S+ from highly correlated SCEP-CEPA wave functions. The equilibrium geometry of H3S+ is predicted to be re =1.350 A(ring) and θe =32.2°. The vibrational frequencies of H323S+ (in cm−1) were calculated to be 2529 (ν1), 1050 (ν2), 2527 (ν3), and 1208 (ν4) which are all in close agreement with experimental values obtained for solid H3S+SbF−6. The computed proton affinity for H2S of PA298=716.7 kJ mol−1 is in very good agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451703
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