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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Photodissociation spectroscopy of Zn+(C2H4) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 5823-5829 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the spectroscopy and photochemistry of Zn+(C2H4) in an angular reflectron time-of-flight mass spectrometer. We identify four absorption bands in the spectral range 220–550 nm. These bands are assigned to radiative transitions in the bimolecular complex correlating with Zn-centered and ethylene-centered absorptions, and with Zn–ethylene photo-induced charge transfer processes. The lowest energy band, assigned as 1 2B2←1 2A1, is a weak continuum consistent with a large geometry change and fast predissociation. The higher energy 1 2B1←1 2A1 band shows a long progression in the intermolecular stretch with a mode frequency of ωe=333.7 cm−1. The spectroscopic results, including partially resolved rotational structure, are consistent with a weakly bound, π-bonded complex in C2v symmetry. A Birge–Sponer analysis gave an estimate for the dissociation energies of the excited 1 2B1 state as De′=2.76 eV and the ground 1 2A1 state as De″=0.86 eV. A second structured band at still higher energies is tentatively assigned as 2 2B2←1 2A1 and shows activation of higher frequency intramolecular ethylene modes. Zn+ and C2H4+ fragment ions are observed over most of the spectral range. At higher energies (λ〈250 nm) we also see a significant branching to reactive products C2H2+ and C2H3+ that result from charge transfer accompanied by C–H bond cleavage. We propose a reaction mechanism that involves coupling through an excited charge-transfer state followed by C–H bond insertion. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1399299
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  • 4
    Electronic Resource
    Electronic Resource
    Photodissociation spectroscopy of Al+-acetaldehyde (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 4847-4852 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the photodissociation spectroscopy of the Al+-acetaldehyde bimolecular complex over the spectral range 212–345 nm. We find evidence for three overlapping molecular absorption bands in the near UV. Two of the bands are unstructured and are assigned as 1A″ and 2A″←1A′. These continuum bands are of mixed character with contributions from Al+-centered 3pπ(A″)←3sσ(A′), acetaldehyde-centered π*(A″)←n(A′), and Al-acetaldehyde charge transfer excitation processes. The third absorption band at short wavelengths, λ〉223 nm, shows a prominent vibrational progression with a mode frequency ωe=210±4 cm−1. The structured band is assigned as 2A′←1A′ and correlates to an Al+-centered 3pπ(A′)←3sσ(A′) radiative transition; the vibrational progression is assigned to the intermolecular Al+-acetaldehyde in-plane bend. Spectroscopic results are in good agreement with ab initio predictions. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1452729
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  • 5
    Electronic Resource
    Electronic Resource
    Photodissociation spectroscopy of Ca+(C2H4) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 6583-6589 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have studied Ca+(C2H4) by photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer over the spectral range 440–790 nm. Ca+ is the only photofragment observed. We find four absorption bands of the complex and assign them to metal-centered transitions correlating with excitation of Ca+(3d and 4p). Spectral assignment is supported by ab initio electronic structure calculations of the complex and isotope substitution experiments. Calculations find a weakly bound ground state equilibrium structure with C2V π-bonding geometry and a dissociation energy of De″=0.506 eV. Theoretical and experimental results show the 4pπ(2 2B2 & 2 2B1) excited states to be relatively weakly bound at long range. Spectral analysis gives vibrational constants for the Ca+--C2H4 intermolecular a1-stretch in the 1 2A1, 2 2B1, and 2 2B2 states, and for the CH2–CH2 a1-wag and the HCH a1-bend in 2 2B2. The results offer an interesting comparison with previous studies of similar weakly bound bimolecular complexes of light metal ions with alkene or alkane hydrocarbons. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481231
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  • 6
    Electronic Resource
    Electronic Resource
    Photodissociation spectroscopy of Mg+–acetaldehyde (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 10288-10293 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have investigated the photodissociation spectroscopy of the Mg+–acetaldehyde bimolecular complex over the spectral range 220–400 nm. We find evidence for four distinct absorption bands in the near ultraviolet that correlate with Mg+-based and acetaldehyde-based transitions. Our results suggest that the Mg+-centered 3pπ(A″)←3sσ(A′) and acetaldehyde-centered π*(A″)←n(A′) transitions are mixed, and result in significant vibrational excitation in the complex leading to broad and unresolved absorption bands. In contrast, the predominantly Mg+-based excitation bands, assigned as 3pπ(A′)←3sσ(A′) and 3pσ(A′)←3sσ(A′), each show prominent vibrational progressions identified with intermolecular wagging modes of the complex. These intermolecular wag progressions are short and anharmonic indicating low barriers to isomerization. In the 3pσ(A′)←3sσ(A′) band several higher frequency vibrational modes are also active and have been assigned to the Mg–OCHCH3 intermolecular stretch, a CCO deformation mode, and the C–O stretch. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1374579
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Electronic orbital alignment effects in the reaction Mg*(3p 1P1)+CH4→MgH+CH3 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6476-6480 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the final state resolved far-wing action spectra for the MgCH4 reactive collision system. The results show a dramatic "Π-like'' orbital alignment preference in the reaction channel. The reactive channel action spectra for different MgH rotational states in v=0 are identical, suggesting that the reaction follows from a single approach geometry, with the product rotational distribution determined by exit channel effects. Based on these observations and molecular orbital considerations, we propose that the reaction proceeds in η2 approach geometry through a triangular C–Mg–H transition state. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469362
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  • 9
    Electronic Resource
    Electronic Resource
    A classical path theory of collisional redistribution in CaHe spin-changing energy transfer collisions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 10485-10492 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have applied a semiclassical (classical path quantum close-coupling) nonadiabatic theory of collisional redistribution to model Ca–He spin-changing energy transfer collisions. The theory predicts the total far wing absorption and final state resolved action spectra. The semiclassical model predictions are in excellent agreement with full quantum mechanical close-coupling calculations [J. Chem. Phys. 95, 5861 (1991)] and both are in good accord with the experimental observations. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467867
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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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