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  • 1
    Electronic Resource
    Electronic Resource
    Hund's case (e): Application to Rydberg states with a 2Π ionic core (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5898-5901 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Rydberg states of high n belonging to series converging to an ion state with a nonzero spin–orbit splitting must be described in so-called Hund's case (e). The derivation of the wave function obtained by transition from case (a) to case (e) is given. Application is made for a 2Π ionic core. This scheme is particularly useful to understand, for example, rotationally resolved spin–orbit autoionization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459499
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  • 2
    Electronic Resource
    Electronic Resource
    Competition between autoionization and predissociation in the HCl and DCl molecules (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7176-7183 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental photodissociation cross sections for HCl and DCl have been recently measured in the autoionization energy region. These cross sections are obtained from the fluorescence excitation spectra of the fragments in the visible [White et al., J. Chem. Phys. 87, 6553 (1987)] or VUV [Frohlich et al. (to be published)] energy region. The peaks observed between 770–900 A(ring) in the photodissociation cross sections do not appear in the same place as that observed in the photoionization cross sections. A theoretical explanation of this fact is proposed. The Rydberg states with a A 2 Σ+ core are predissociated due to the spin–orbit interaction, by Rydberg states belonging to series converging to the repulsive a 4 Π state of HCl+ . Using an unified MQDT treatment of autoionization and predissociation processes, the photoionization and photodissociation cross sections are calculated and compared with the experimental results. It is concluded that the states which are predissociated do not have the same symmetry as the states which are autoionized by the continuum of the X 2 Π state. The photodissociation cross section in HCl represents only a few percent of the photoionization cross section. It is predicted that for the heavier molecule HBr, the photodissociation cross section would be more than 10% of the photoionization cross section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456247
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  • 3
    Electronic Resource
    Electronic Resource
    Multiphoton ionization vs multiphoton dissociation: Competition between photoionization and dissociation in CO (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4272-4276 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The competition between photoionization and spontaneous dissociation involving the 3Π states of CO has been investigated both experimentally and theoretically. In this study we analyzed the mass and kinetic energy spectra of the photofragments generated after irradiating CO with a line narrowed (≈0.75 cm−1) tunable ArF* laser (λ≈193 nm) and calculated the cross section (3.2 Mb) for photoionizing the c 3Π Rydberg state of CO at the excitation energy. The basic conclusions of this study are that the interaction between the 3Π Rydberg states and the 3Π valence states near 12.8 eV causes rapid (picosecond time scale or faster) dissociation of CO which impedes photoionization and that multiphoton dissociation completely dominates multiphoton ionization at laser power densities up to at least 30 GW/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457786
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of the autoionization in the calculation of the fluorescence polarization for the A 2Πu –X 2Πg transition in O+2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2691-2696 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An ab initio calculation of the fluorescence polarization including autoionization is made in the case of O+2, using the multichannel quantum defect approach. If only the states belonging to Rydberg series converging to the b 4∑−g state of O+2 are included, due to their narrow ab initio calculated autoionization widths, the values of the polarization of the A 2Πu −X 2Πg fluorescence is found to be negative in the 73–69 nm wavelength region, in contradiction with recent experiments [Keller et al., J. Chem. Phys. 87, 3299 (1987)]. Good agreement with experimental results is obtained only in taking into account the influence of the 3∑−u Rydberg state (B 2∑−g) 4pσu, which enlarges the autoionized peaks either by perturbation or by predissociation. There results are compared to the qualitative theoretical interpretation of Keller et al. in terms of two 3∑−u valence states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455020
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  • 5
    Electronic Resource
    Electronic Resource
    Photoionization of jet-cooled HI with coherent vacuum ultraviolet radiation: Evidence for Hund's case (e) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1676-1687 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In the range of 83 500–89 200 cm−1, the photoionization spectrum of HI is strongly influenced by autoionization of Rydberg series converging to the higher lying 2Π1/2 component of the spin–orbit split 2Π ionic ground state. The photoelectron yield spectrum, exhibiting the various autoionization processes, has been measured on a rotationally cooled sample (Trot∼13 K), with a spectral resolution of the exciting vacuum ultraviolet radiation of 0.5 cm−1. Using a multichannel quantum-defect theory treatment explicitly including rotation, we calculate spin–orbit and rotational autoionization fine structure in the spectrum. In order to find a qualitative agreement of theory and experiment, the Rydberg states of HI have to be described in terms of a transition in angular momentum coupling cases, going from Hund's case (c) to case (e).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461783
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  • 6
    Electronic Resource
    Electronic Resource
    Ion-pair formation in the photodissociation of HCl and DCl (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4986-4992 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrationally resolved excitation functions for Cl− formation from jet-cooled HCl and DCl, following photoabsorption in the region 75–86 nm (HCl/DCl+hν→H+/D++Cl−), are reported and compared with ab initio calculations. This completes our understanding of the various possible decay channels available to superexcited states of HCl and DCl that lie above the first ionization limit. Our experimental and theoretical results suggest that the Rydberg states responsible for ion-pair formation in HCl and DCl via predissociation by the V 1Σ+ ion-pair state correspond to 1Σ+ states that are only weakly autoionized. These same Rydberg states appear to act as, at least, one class of precursor states for neutral dissociation to yield excited H* and Cl* atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466000
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  • 7
    Electronic Resource
    Electronic Resource
    Rotationally resolved single-photon ionization of HCl and DCl (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2300-2306 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotationally resolved photoionization yields of jet-cooled HCl and DCl have been measured in the energy range between their spin–orbit split 2Π ionic thresholds. For single-photon excitation, narrow-band vuv radiation is generated by resonant frequency mixing. The spectra are complex due to an interaction of autoionizing resonances belonging to series converging to different rotational states of the ion core. This is taken into account using the multichannel quantum defect theory in a treatment capable to handle a transition in angular momentum coupling from Hund's case (c) to case (e). Even for Rydberg orders n(approximately-greater-than)35 the experimental data cannot be explained using a pure case (e) picture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465245
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  • 8
    Electronic Resource
    Electronic Resource
    Spin–orbit and rotational autoionization in HCl and DCl (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2287-2299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotationally resolved spin–orbit autoionization spectrum of HCl has been obtained in double resonance via levels of lowest angular momentum in v=0 of the 4pσ D 1Π state. A self-consistent assignment is offered for the portion of the spectrum ranging over principal quantum numbers from 13 to 18. Positions established in HCl point to series of similar quantum defect converging to the rotational ground state of DCl+ 2Π1/2. HCl features are further confirmed by comparison with earlier double-resonance spectra obtained via the F 1Δ state, and with vuv autoionization spectra observed in single-photon transitions from the neutral ground state. Multichannel quantum defect theory calculations have been carried out, which introduce 28 parameters corresponding to the quantum defects, transition moments, and s–d l-mixing coefficients for Rydberg states of HCl in Hund's case (a). As output they predict positions and intensities for transitions involving all 53 channels accessible in Hund's case (e) for l ranging from 0 to 2 and J from 1 to 2. The same parameters for both isotopes yield reasonable correspondence between experiment and theory for all the major resonances in HCl and DCl from principal quantum number 13 to 18 (about 70 resonances), with an average ΔE less than 3 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465244
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  • 9
    Electronic Resource
    Electronic Resource
    On the vibrational autoionization in NO2 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7657-7658 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational autoionization for NO2 is evaluated by ab initio calculations and compared to recent experimental results of Grant et al. It is concluded that the resonances are broader for symmetric stretching than for asymmetric stretching as in the case observed, but this conclusion depends of the nature of the Rydberg orbital.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464682
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamics of high-n Rydberg states employed in zero kinetic energy-pulsed field ionization spectroscopy via the F 1Δ2, D 1Π1, and f 3Δ2 Rydberg states of HCl (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5702-5710 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The intensity anomalies in the spin–orbit and rotational branching ratios in the zero kinetic energy pulsed-field ionization (ZEKE-PFI) spectra via the F 1Δ2, D 1Π1, and f 3Δ2 Rydberg states of HCl have been studied. In general, the branching ratios are observed to depend on three parameters employed in the pulsed field ionization experiment: (i) the delay time between excitation and ionization; (ii) the magnitude of the bias electric field; and (iii) the magnitude of the applied pulsed electric field. The results can be rationalized on the basis of the increasing number of autoionization decay channels that become available to the high-n Rydberg states as each ionization threshold is surpassed. The delay dependence of the ZEKE-PFI spectra via the F 1Δ2 state has been analyzed in more detail by ab initio calculations. These calculations show that the observed spin–orbit branching ratios can be reproduced thereby giving evidence for a nonexponential decay of the high-n Rydberg states (n≈100). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472415
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