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  • 1
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2216-2234 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report a two-color high-resolution energy- and angle-resolved study of the photoelectrons produced in the (1+1') REMPI of NO via rotational levels of the A 2Σ+ v=0 state. We find markedly different photoelectron angular distributions arising from production of ions in different rotational states (ΔN=0,±1,±2 transitions in the ionization step). We also observe that the ΔN=±2 angular distributions are very sensitive to the intermediate state alignment. A model is put forward in which experimental observables (angle- and energy-resolved photoelectron spectra) are used to determine the attributes (relative amplitudes and phase shifts) of a small number of interfering continuum channels that contribute to the ionization step as well as the fraction of parallel character of the ionization step. Nearly 70% of the ejected photoelectrons are associated with the ΔN=0 ionization transition; the partial wave composition of these electrons is dominated by p character. The less important ΔN=±1 peaks have both s- and d-wave character. The ΔN=±2 photoelectron peaks exhibit far more f-wave than p-wave character because destructive interference nearly removes the p-wave contribution to the angular distribution. The partial wave decomposition is used to predict angular distributions resulting from excitation of the intermediate state by different rotational branch transitions; these predictions are in excellent agreement with the measured distributions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1757-1767 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-of-flight photoelectron spectroscopy has been used to record energy-resolved photoelectron angular distributions (PADs) following (1+1') resonance-enhanced multiphoton ionization (REMPI) of NO via the vi=1,Ni=22 rovibrational level of the A 2∑+ state. The PADs corresponding to single rotational states of the resulting molecular ion show a strong dependence on the change in ion core rotation ΔN(≡N+−Ni) and also on the angle between the linear polarization vectors of the two light beams. Broken reflection symmetry [I(θ,φ)≠I(−θ,φ)] is observed when the polarization vectors of the two light beams form an angle of 54.7°. A fit to the PADs provides a complete description of this molecular photoionization, namely, the magnitudes and phases of the radial dipole matrix elements that connect the intermediate state to the ||lλ〉 photoelectron partial waves (Refs. 1 and 2). This information is then used to predict unobserved quantities, such as ion angular momentum alignment and the full three-dimensional form of the PADs.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1746-1756 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An expression is derived for the photoelectron angular distribution (PAD) following (1+1') resonance-enhanced multiphoton ionization (REMPI) of a molecule with linearly polarized light beams. When the two polarization vectors are parallel, cylindrical symmetry exists, and the PAD depends only on θ, the angle between the linear polarization vector of the ionizing radiation and the electron ejection direction. When the polarization vectors are perpendicular, cylindrical symmetry is broken, and the PAD shows φ and θ dependence. For an arbitrary angle between the two polarization vectors, the angular distribution ceases to have reflection symmetry. This breaking of cylindrical symmetry causes interference effects in the REMPI process that are readily described using a density matrix formalism. As an example, the (1+1') REMPI of NO via its A 2Σ+ state is considered.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 8154-8158 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5026-5039 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spectroscopy and dissociation dynamics of the N2O−2(C2v) anion have been investigated using the technique of fast ion beam translational spectroscopy. A newly developed pulsed supersonic discharge source is described for the production of internally cold N2O−2. A structured absorption band beginning near 580 nm is observed, and is assigned to the B˜(2A2)←X˜(2B2) transition with the aid of ab initio calculations. Two dissociation channels from the upper state are observed: (1) O−+N2O and (2) NO−+NO. Translational energy and angular distributions are measured for both channels at several excitation energies. The translational energy distribution for channel (1) at 570 nm shows resolved structure corresponding to N2O vibrational excitation. The translational energy distributions for channel (1) are reasonably well described by prior distributions, indicating this channel results from dissociation from the N2O−2 ground electronic state. In contrast, channel (2) appears to result from dissociation on a repulsive excited electronic state. From the translational energy distributions for channel (1), we obtain the bond dissociation energy and heat of formation (at 0 K) for N2O−2: D0(O–N2O)=1.40±0.03 eV and ΔH0f,0(N2O−2)=0.58±0.04 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 2495-2508 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The predissociation of the O2B 3Σ−u state (υ=0–11) is investigated using fast beam photofragment translational spectroscopy. The energy resolution of the experiment, 7–10 meV, is sufficient to yield the correlated fine structure distribution P(j1,j2) for the two O(3Pj) fragments. These spin–orbit branching ratios depend markedly on the vibrational quantum number, providing detailed insight into a relatively unexplored facet of molecular dissociation dynamics. No less than four repulsive states are expected to mediate the predissociation of the B 3Σ−u state, primarily via spin–orbit coupling, and the couplings among these states at long range (R∼5–7 A(ring)) determine the final spin–orbit distributions P(j1,j2). We have attempted to model these distributions in both the adiabatic and diabatic limits, with neither limit proving very successful. A more phenomenological approach to fitting our data suggests that products with j1=j2=2 result from single transitions between adiabatic potentials at long range, whereas the populations in the other product states are determined by multiple transitions among the repulsive states. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 4948-4957 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoionization process NO A 2Σ+ (v=0, N=22)→NO+ X 1Σ+ (v+=0, N+)+e− is studied with sufficient photoelectron energy resolution that the photoelectron angular distributions (PADs) associated with individual rotational levels N+ of the ion are determined. By ionizing with left and right circularly polarized light and observing the change in the rotationally resolved PADs, we can deduce all dynamical information, including the signs of the relative phase shifts of the photoelectron partial waves. This information constitutes the first complete description of the photoionization of a molecule. We discuss the consistency of our dynamical parameters with the Rydberg series of NO. We present a general formalism for (1+1') resonance-enhanced multiphoton ionization (REMPI) PADs for rotationally resolved ion states using linearly polarized light for excitation and elliptically polarized light for ionization. Based on the dynamical parameters determined from our fit, we use this formalism to predict the total system state, i.e., three-dimensional PADs and polarization of ion rotational levels following photoionization.
    Type of Medium: Electronic Resource
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