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  • 1
    Electronic Resource
    Electronic Resource
    Nascent rotational quantum state distribution of NaH (NaD) from the reaction of Na*(4 2P) with H2, D2, and HD (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 213-217 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The nascent rotational quantum state distributions of NaH and NaD products resulting from the reactions of Na*(4 2Pj) with H2, D2, and HD have been determined using the laser pump–probe technique. We have observed a bimodal rotational distribution with a minor component peaking at low J and a major component peaking at high J. We have observed no evidence for a kinematic isotope effect on the product distribution. Our results are consistent with a model wherein the reaction occurs predominantly on the attractive 2B2 potential energy surface in near C2v geometry with the rotational distribution being determined late in the exit channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462507
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  • 2
    Electronic Resource
    Electronic Resource
    Reactive collision dynamics of Na*(4 2P)+H2 and HD: Experiment and theory (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 218-229 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used a "half-collision'' pump–probe technique to measure the far wing absorption profiles of the NaH2 collision complex leading to the nonreactive formation of Na* and to four distinct final rotational states of the reaction product NaH(v‘=1, J‘=3, 4, 11, and 13). We have observed reaction on both the attractive potential energy surfaces and over a barrier on the repulsive surface. We have observed the effect of the Na* reagent electronic orbital alignment on the NaH final product rotational state distribution. Specifically, absorption to the repulsive surface leads preferentially to low-rotational product states, while absorption to the attractive surfaces leads preferentially to high-rotational product states of NaH. Isotopic substitution experiments give evidence of a kinematic isotope effect on the product rotational state distribution for reactive trajectories on the repulsive surface. We have developed a simple model using a quantum mechanical line shape calculation to estimate the NaH2 absorption probability as a function of wavelength. We then make simple phenomenological dynamical arguments to predict final state branching. There is an overall qualitative agreement between the experimental results and theoretical model predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462508
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  • 3
    Electronic Resource
    Electronic Resource
    Photodissociation of K2 (X 1Σ+g–B 1Πu) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4168-4176 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A semiclassical model based on an orbital following picture to describe the dissociation dynamics of K@B|2 (B 1Πu) is outlined. The results of this simple model are in complete quantitative agreement with an exact quantum calculation by Dubs and Julienne based on a half-collision multichannel quantum defect analysis (accompanying paper). These theoretical works give a complete description of the process and indicate that dissociation occurs adiabatically from the Hund's case (a) to the Hund's case (c) basis, followed by a sudden recoupling at long range to the Hund's case (e) basis. The experimentally observed bound–free excitation spectrum and the polarization of the atomic product fluorescence are in excellent agreement with the result of a full thermally averaged calculation based on this theoretical dynamical model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460772
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  • 4
    Electronic Resource
    Electronic Resource
    Alignment effects in Ca–He (5 1P1−5 3PJ) energy transfer half-collisions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7605-7606 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456195
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  • 5
    Electronic Resource
    Electronic Resource
    Alignment effects in Ca–He(5 1P1–5 3PJ) energy transfer collisions by far wing laser scattering (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4771-4776 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The far wing absorption profiles for excitation on the Ca(4s2 1S0–4s5p 1P01) atomic transition, broadened in collisions with He are measured. We observe strong absorption in both wings and a blue wing satellite near Δ∼125 cm−1. We tentatively identify this satellite as due to a maximum in the CaHe(4s2 1∑+–4s5p 1∑+) difference potential. These line-broadening techniques are used to study electronic energy transfer in the spin-changing collisions of Ca with He: Ca(5p 1P01) +He→Ca(5p 3P0J)+He+ΔE. Measurements of the "single collision'' triplet–singlet branching ratio as a function of laser detuning from the atomic resonance frequency indicate a clear red wing/blue wing asymmetry. We interpret this asymmetry in terms of a preferential orbital alignment effect in the energy transfer process [Phys. Rev. Lett. 53, 2296 (1984)]. No clear structure is observed in the range of detunings probed that might indicate the curve crossing responsible for the energy transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455671
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  • 6
    Electronic Resource
    Electronic Resource
    Erratum: Reactive collision dynamics by far wing laser scattering: Mg+H2 [J. Chem. Phys. 85, 5493 (1986)] (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7783-7783 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461835
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  • 7
    Electronic Resource
    Electronic Resource
    Collisional energy transfer in Na(4p–3d)–He,H2 collisions (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 1101-1104 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the direct collisional energy transfer process Na*(4p)+M→Na*(3d)+M, where M=He,H2 under gas cell conditions. We have measured the temporal profiles of the Na(3d–3p) sensitized fluorescence as a function of quenching gas pressure and fit the profiles to a two-state rate equation model to obtain the quenching rate coefficients from the Na*(4p) state. The total energy transfer rate coefficient out of the 4p state for He is small [(0.5±0.2)×10−10 cm3/s]. The total quenching rate coefficient out of the 4p state is much larger for H2[(3.9±0.5)×10−10 cm3/s]. Evidence suggests that the energy transfer rate coefficient for the 4p–3d process is ∼2.0×10−10 cm3/s with the remainder of the 4p quenching being predominantly reactive. We also compare the far-red wing absorption line shapes for the NaHe and NaH2 systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464333
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  • 8
    Electronic Resource
    Electronic Resource
    Photodissociation spectroscopy of MgCH+4 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 6452-6459 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation spectroscopy of MgCH+4 has been studied in a reflectron time-of-flight mass spectrometer. MgCH+4 molecular absorption bands are observed to the red of the Mg+(3 2PJ←3 2S1/2) atomic ion resonance lines. The photofragmentation action spectrum consists of a broad structureless continuum ranging from 310 nm to 342 nm, and peaking near 325 nm. In this spectral region, both the nonreactive (Mg+), and two reactive fragmentation products (MgH+ and MgCH+3) are observed, all with similar action spectra. The product branching is independent of wavelength, Mg+:MgCH+3:MgH+∼60:33:7. The absorption is assigned to the transition (1 2E←1 2A1) in C3v symmetry (with η3 coordination), followed by a geometrical relaxation of the complex toward states of 2B1 and 2B2 symmetry in C2v geometry (with η2 coordination). Dissociation requires a nonadiabatic transition to the ground electronic surface. Analysis of broadening in the photofragment flight time profile shows the nonreactive Mg+ product angular distribution to be isotropic, with an average translational energy release which increases slightly from Et∼370±150 cm−1 at 332.5 nm to Et∼520±180 cm−1 at 315 nm. These values are less than 2% of the available energy and are well below statistical expectations. Analogous experiments on MgCD+4 show the kinetic energy release in the nonreactive channel to be significantly larger for the CD4 case, ranging from Et∼540±180 cm−1 at 332.5 nm to Et∼830±200 cm−1. These results clearly demonstrate that the dissociation is nonstatistical. Preliminary ab initio potential surface calculations suggest a possible dynamical mechanism to explain these unusual results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471366
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  • 9
    Electronic Resource
    Electronic Resource
    Collisional redistribution in Sr–He spin-changing energy transfer collisions: Final-state alignment (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1917-1924 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the product alignment resulting from the collisional redistribution of polarized light in Sr–He inelastic spin-changing energy transfer collisions. The experimental results are in good agreement with the predictions of an analytic theoretical model, based on a standard orbital-locking and following approximation, but generalized to this inelastic collision process. The good agreement indicates a clear understanding of the energy transfer dynamics in this case, and suggests that this simple analytic approach may be generalized to a much broader range of collisional phenomena. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468757
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  • 10
    Electronic Resource
    Electronic Resource
    Photofragmentation dynamics of Mg2(CO2)+1,2 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 5235-5245 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the photofragmentation spectroscopy of Mg2(CO2)+1,2 in a reflectron time-of-flight mass spectrometer. For the linear bimolecular complex Mg2(CO2)+, we have observed three distinct molecular absorption bands, in the red, the green, and the near uv spectral regions. In each band both Mg+ and Mg+2 fragments are observed, although with different action spectra. In the uv band, we also observe reactive fragmentation to form the chemical product Mg2O+. As an initial step in investigating the dissociation mechanism and the dynamical effects which determine the final state branching, we have carried out preliminary calculations of the low lying Mg2(CO2)+ potential energy curves in collinear geometry. Photofragmentation of the complex Mg2(CO2)+2 occurs over a broad spectral range in the visible. We have found that the addition of the second solvent molecule dramatically enhances the solvent cage effect, as evidenced by a large increase in the Mg+2/Mg+ branching ratio throughout this spectral region. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469249
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