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  • 1
    Electronic Resource
    Electronic Resource
    Vibrationally resolved cross sections for single-photon ionization of LiH (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6724-6734 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio studies of the single-photon ionization of LiH(X 1Σ+) leading to LiH+(X 2Σ+) are reported. The process is studied as function of the internuclear distance (2 a.u.–6 a.u.) and the kinetic energy of the electron (0.05 eV–10 eV). The calculations are based on the so-called iterative Schwinger approach which is implemented within the frozen-core single center approximation. By comparing vibrationally resolved cross sections calculated beyond and within the Franck–Condon principle we find, that the Franck–Condon principle applies relatively well to the present photoionization process. The vibrational wave functions needed for these calculations are obtained from very accurate CI-potentials, also reported in this paper. For LiH the first 10 vibrational spacings are found to agree with the experimental data within 0.2%. Photoelectron spectra (PES) calculated under simulated experimental conditions suggest that photoionization experiments on LiH may yield information on the vibrational structure of LiH+. The calculated permanent dipole moment of the LiH ground state shows strong influence of the ion-pair channel (Li+H−). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479970
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  • 2
    Electronic Resource
    Electronic Resource
    (1+1) resonant enhanced multiphoton ionization via the A 2Σ+ state of NO: Ionic rotational branching ratios and their intensity dependence (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1516-1521 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recent high resolution photoelectron spectroscopic studies of the (1+1) resonant enhanced multiphoton ionization (REMPI) of NO via the 0–0 transition of the A–X band (γ band) have shown a pronounced ΔN=0 signal (ΔN≡N+−Ni) and smaller, but measurable, ΔN=±2 peaks. The authors [K. S. Viswanathan et al., J. Phys. Chem. 90, 5078 (1986)] assign the excitation to be via an R(21.5) line, with no further specification. We have performed ab initio calculations of the rotational branching ratios for the four possible "R(21.5)'' transitions, namely, the rotationally "clean'' R21 and R22, and the "mixed'' R12+Q22 and R11+Q21 branches. We find the mixed R12+Q22(21.5) branch to agree best with the observed photoelectron spectrum collected parallel to the polarization vector of the light. The discrepancy is larger for detection perpendicular to the polarization. To understand this difference, we have assessed the influence of laser intensity and polarization "contamination'' on the branching ratios and photoelectron angular distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454130
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  • 3
    Electronic Resource
    Electronic Resource
    Photoionization cross sections of rovibrational levels of the B 1Σ+u state of H2 (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 6657-6661 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report theoretical cross sections for direct photoionization of specific rovibrational levels of the B 1Σ+u electronic state of H2. The calculated cross sections differ considerably from values recently determined by resonant enhanced multiphoton ionization (REMPI) studies. In an attempt to understand the disagreement, we analyze in detail the REMPI dynamics and find that the multiphoton ionization probability is extremely sensitive to the spatial and temporal profiles of the laser pulses. Accurate characterization of laser profiles and their jitter is therefore necessary for a comparison between theory and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450718
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  • 4
    Electronic Resource
    Electronic Resource
    (2+1) resonant enhanced multiphoton ionization of H2 via the E,F 1Σ+g state (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1748-1751 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper, we report the results of ab initio calculations of photoelectron angular distributions and vibrational branching ratios for the (2+1) REMPI of H2 via the E,F 1Σ+g state, and compare these with the experimental data of Anderson et al. [Chem. Phys. Lett. 105, 22 (1984)]. These results show that the observed non-Franck–Condon behavior is predominantly due to the R dependence of the transition matrix elements, and to a lesser degree to the energy dependence. This work presents the first molecular REMPI study employing a correlated wave function to describe the Rydberg–valence mixing in the resonant intermediate state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452174
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  • 5
    Electronic Resource
    Electronic Resource
    (2+1') rotationally resolved resonance enhanced multiphoton ionization via the E 2∑+(4s,3d) and H 2∑+(3d,4s) Rydberg states of NO (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7054-7065 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of studies of ionic rotational branching ratios and photoelectron angular distributions resulting from (2+1') resonance enhanced multiphoton ionization of NO via various high J (≈21.5) rotational branches of the E2∑+(4s,3d) and H2∑+(3d,4s) Rydberg states are presented. The rotational branching ratios show the expected ΔN=even rotational propensity rule with very small ΔN=odd signals. The branching ratios for the E2∑+ state are seen to be independent of photoelectron energy with the ΔN=+2 signals strongest and no appreciable higher rotational transfer peaks (||ΔN||≥3). The higher rotational transfer signal for ionization of the H2∑+ state are also negligible but the rotational branching ratios are strongly energy dependent due to a Cooper minimum in the l=3 partial wave of the kσ- and kπ-continua at a photoelectron kinetic energy of 2.6 eV and 2.9 eV, respectively. This leads to a strong rotational selectivity that can be exploited to produce ions in a specific rotational level. These consequences of Cooper minima close to threshold are quite general and their influence on rotational distributions should be readily observable in other molecular systems. The photoelectron angular distributions via both states show a strong energy dependence with a rapid change in the angular distributions around the Cooper minimum associated with the H2∑+ state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459428
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  • 6
    Electronic Resource
    Electronic Resource
    Cooper minima and circular dichroism in photoelectron angular distributions (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7513-7514 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We demonstrate that circular dichroism in photoelectron angular distributions (CDAD), resulting from resonance enhanced multiphoton ionization (REMPI) of an aligned molecular Rydberg state, is a highly sensitive probe of the presence of a Cooper minimum near threshold. To illustrate this application of CDAD, we present the results of ab initio calculations for (1+1') REMPI via the R21(5.5) branch of the D 2Σ+(3pσ) state of NO, where a Cooper minimum is found in l=2 (d wave) of the kπ continuum at a photoelectron kinetic energy of 3.2 eV. The CDAD signal is found to vary rapidly with photoelectron kinetic energy, go through zero, and change sign in the region of the Cooper minimum. This result is predicted by CDAD theory for photoionization from an aligned atomic p orbital.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459377
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  • 7
    Electronic Resource
    Electronic Resource
    Vibrational state dependence of ionic rotational branching ratios in resonance enhanced multiphoton ionization of CH (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1374-1376 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show that rapid evolution of a Rydberg orbital with internuclear distance in a resonance enhanced multiphoton ionization (REMPI) process can have a profound influence on the production of molecular ions in alternative rotational states. This is illustrated by calculations of ionic rotational branching ratios for (2+1') REMPI via the O11 (20.5) branch of the E' 2Σ+(3pσ) Rydberg state of CH. The rotational propensity rule for ionization changes from ΔN=odd (ΔN=N+−Ni) at lower vibrational excitation, as expected from the ΔN+l=odd selection rule, to ΔN=even at higher vibrational levels. This effect is expected to be quite general and should be most readily observable in diatomic hydrides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457161
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  • 8
    Electronic Resource
    Electronic Resource
    Rotational branching ratios at low photoelectron energies in resonant enhanced multiphoton ionization of NO (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2570-2574 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report calculated rotational branching ratios for very low energy (50 meV) photoelectrons resulting from (1+1') resonant enhanced multiphoton ionization (REMPI) via the Ji =1/2, 3/2, 5/2, and 7/2 levels of the P11 branch of the A 2Σ+ (3sσ) state of NO. Even angular momentum transfer (ΔN≡N+−Ni) peaks are dominant in these rotational distributions, in agreement with the selection rule ΔN+l=odd. Angular momentum coupling in the photoelectron wave function arising from the molecular ion potential leads to smaller but appreciable ΔN=odd peaks. The calculated ΔN=0 to ΔN=+2 peak ratios show the same strong decrease when Ji increases from 1/2 to 3/2 as seen in the experimental zero-kinetic-energy (ZEKE) photoelectron spectra [Sander et al., Phys. Rev. A 36, 4543 (1987)], but do not show the rapid die-off of the ΔN≠0 peaks for higher Ji observed experimentally. The calculated trend in the ΔN=+2 vs ΔN=0 peaks could be understood on the basis of simple angular momentum transfer arguments. These same arguments indicate that this trend in the ΔN=0 and +2 peaks with increasing angular momentum is not generally expected in other branches. Spectra via the R21 ( J) branch are presented to support this assertion. We also present photoelectron angular distributions which show a strong dependence on ΔN reflecting the changing composition of the photoelectron wave function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455953
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  • 9
    Electronic Resource
    Electronic Resource
    Erratum: (1+1) resonant enhanced multiphoton ionization via the A 2Σ+ state of NO: Ionic rotational branching ratios, and their intensity dependence [J. Chem. Phys. 88, 1516 (1988)] (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2591-2591 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455738
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  • 10
    Electronic Resource
    Electronic Resource
    Submillimeter wave spectroscopy of XeH+ and XeD+ (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2352-2360 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The J=0–1 rotational transition of XeH+ and the J=1–2 transition of XeD+, which both occur near 390 GHz, have been studied by microwave absorption spectroscopy. For each of these all nine naturally occurring stable isotopes of xenon were detected. The magnetic hyperfine structure for the 129Xe forms and the electric quadrupole–magnetic hyperfine structure of both 131Xe forms were fully resolved and analyzed to determine the CI and eQq0 constants. The scaled spin–rotation parameter CI/(gIB) is found to be practically identical in XeH+ and HI, as it is also in the isoelectronic pair KrD+ –DBr/HBr. The available magnetic field was too small to resolve the rotational Zeeman effect, but the rotational g factor of XeH+ was estimated from Zeeman broadening. The mass-independent Dunham parameters U01, ΔH01, and ΔXe01 were determined from the very accurate microwave frequencies combined with higher order Dunham coefficients from published Fourier-transform infrared (FTIR) spectroscopy of XeH+ . Although it was not practical to observe XeH+ or XeD+ in excited vibrational states, we were able to detect the J=0–1 (v=1) transition of ArD+ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460941
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