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  • 1
    Electronic Resource
    Electronic Resource
    The ultraviolet photodissociation of Cl2O at 235 nm and of HOCl at 235 and 266 nm (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 1315-1323 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The primary photochemistry of gas phase dichlorine monoxide (Cl2O) and of hypochlorous acid (HOCl) following excitation at 235 nm has been investigated using photofragment ion imaging to obtain the recoil velocity and angular distributions of the ground (2P3/2) and spin-orbit excited (2P1/2) atomic chlorine products. In the case of Cl2O, both Cl spin-orbit products exhibit angular distributions characterized by an anisotropy parameter, β=1.2±0.2, consistent with previous interpretations of the ultraviolet (UV) absorption spectrum of Cl2O which associate the broad intense absorption feature peaking at λ∼255 nm with excitation to a (bent) dissociative state of 1B2(C2v) symmetry. The recoil velocity distributions of the two Cl spin-orbit products are markedly different. The ground state atoms (which constitute 〉90% of the total Cl atom yield) are partnered by ClO fragments carrying significantly higher average levels of internal excitation. The slowest Cl atoms are most readily understood in terms of three body fragmentation of Cl2O to its constituent atoms. These findings are rationalized in terms of a model potential energy surface for the 1 1B2 state, which correlates diabatically with ClO(X) radicals together with a spin-orbit excited Cl atom, with efficient radiationless transfer to one (or more) lower energy surfaces at extended Cl-O bond lengths accounting for the dominance of ground state Cl atom fragments. The image of the ground state Cl atoms resulting from photolysis of HOCl at 235 nm is consistent with parent excitation via a transition for which the dipole moment is closely aligned with the Cl-O bond, followed by prompt dissociation (β=1.7±0.2) with the bulk of the excess energy partitioned into product recoil. Such conclusions are consistent with the results of laser induced fluorescence measurements of the OH(X) products resulting from 266 nm photodissociation of HOCl which reveal OH(X) products in both spin-orbit states, exclusively in their zero-point vibrational level, and carrying only modest levels of rotational excitation (well described by a Boltzmann distribution with Trot∼750±50 K). © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476682
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  • 2
    Electronic Resource
    Electronic Resource
    Ion Imaging of the Photodissociation of OCS Near 217 and 230 nm (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 16307-16314 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100044a017
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  • 3
    Electronic Resource
    Electronic Resource
    Control of photofragment velocity anisotropy by optical alignment of CH3I (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 2164-2167 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A molecule placed in an electric field can be aligned because of the anisotropy of its polarizability tensor. As an alternative to high static electric fields, the electric field of a pulsed laser can be used for alignment. The alignment can be demonstrated by measurement of the control of the anisotropy of photodissociated fragments generated by polarized light. Sakai et al. have recently reported such an experiment on aligned iodine molecules [J. Chem. Phys. 110, 10235 (1999)]. This paper reports an independent finding of the same phenomenon with CH3I. General equations are presented for the degree of alignment and its control of the photodissociation amplitude. The control parameter for a symmetric top or linear molecule is −(α−αzz)(E2/2kT)P2(cos χ), where α is the mean polarizability, αzz is the element of the polarizability tensor along the symmetry axis, and χ is the angle between the E vectors of the aligning and dissociating lasers. The fragment velocity anisotropy can be increased or decreased by varying this control parameter. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480782
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  • 4
    Electronic Resource
    Electronic Resource
    Photofragment excitation spectrum for O(1D) from the photodissociation of jet-cooled ozone in the wavelength range 305–329 nm (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 6390-6397 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photofragment excitation (PHOFEX) spectrum for O(1D) production from the photolysis of ozone under supersonic free-jet conditions was measured, scanning the photodissociation wavelength in the region of 305–329 nm and probing the O(1D) atoms by vacuum ultraviolet laser induced fluorescence at 115.2 nm. The bond dissociation energy D00(O2–O) was determined to be 101.53±0.25 kJ mol−1 from the cut-off wavelength in the PHOFEX spectrum for the photodissociation of jet-cooled ozone (Trot(approximate)5 K) to O(1D)+O2(a 1Δg). The cut-off wavelength for vibrationally hot band excitation to the dissociative continuum of O(1D)+O2(a 1Δg) was also observed in the PHOFEX spectrum. It was found that the active mode for the hot band excitation was the antisymmetric stretching mode ν3 in the ground electronic state of ozone. Sharp peaks corresponding to vibrational bands in the Huggins system were also observed in the PHOFEX spectrum of the O(1D) atoms produced via the spin-forbidden dissociation process, O(1D)+O2(X 3∑g−). The spectral widths of the vibronic bands in the Huggins system are discussed in terms of the dissociation dynamics. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473629
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of molecular bending on the photodissociation of OCS (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 7095-7101 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: At 230 nm, the photodissociation of OCS via a hot band and a triplet state was investigated by selective probing of high rotational levels of product CO (J=45–67) with photofragment imaging spectroscopy: OCS(v=0)+hν(UV)→CO(X 1Σ+,J≥65)+S(3P), OCS(v=1)+hν(UV) →CO(X 1Σ+,J∼65)+S(1D). Additional two-photon IR excitation of the UV photoprepared OCS with intense 1.06 μm laser pulses bleaches the UV processes listed above and induces a new excitation channel of OCS: OCS(v=0)+hν(UV)→OCS*, OCS*+2hν(IR)→CO(X 1Σ+,J∼74)+S(1S). The bending mode of OCS in the excited states plays a central role in the excitation and dissociation dynamics. Additionally, the alignment effect of OCS by nonresonant infrared laser pulse, which appears on the angular distribution of the photofragment, is discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481324
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  • 6
    Electronic Resource
    Electronic Resource
    Laser-induced fluorescence detection of ClO radicals at 167–180 nm (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 8262-8263 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: ClO radicals are detected by a laser-induced fluorescence technique, using the C 2Σ–X 2Π transition with a tunable vacuum ultraviolet laser system. Predissociation in the C 2Σ state is discussed in terms of the fluorescence lifetime and excitation spectra. The vibrational distribution of ClO produced by the reaction between O(1D) and HCl is measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468197
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  • 7
    Electronic Resource
    Electronic Resource
    Fine structure branching ratios and translational energies of O(3Pj) atoms produced from collision induced intersystem crossing of O(1D) atoms (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 315-324 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Collision induced intersystem crossing of O(2p 1D) to O(2p 3Pj) j=0,1,2 was studied by vacuum-ultraviolet laser induced fluorescence. The nascent j-branching ratios of O(3Pj) produced from collision of O(1D) with Xe, Kr, N2, CO2, and CF3H at the collision energy of 15.6, 14.7, 11.4, 13.0, and 14.4 kcal/mol are [O(3P0)]/[O(3P1)]/[O(3P2)]=(0.28±0.04)/(0.58±0.05)/1, (0.33±0.05)/(0.45±0.07)/1, (0.23±0.05)/(0.35±0.05)/1, (0.14±0.05)/(0.41±0.05)/1, and (0.20±0.05)/(0.45±0.05)/1, respectively. The j-branching ratios are discussed in terms of potential curve crossing between singlet and triplet surfaces and nonadiabatic nature of the potential surfaces. Doppler profiles of the product O(3Pj) atoms were measured as a function of time delay between pump and probe laser pulses. By calculating the kinetic energy from the Doppler profiles, electronic energy transfer efficiencies to the internal energy of N2, CO, CO2, and CF3H are obtained to be (30±7), (31±7), (49±3), and (52±5)%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467000
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of the spin-forbidden O(1D)+O2(X 3Σg−) channel in the 317–327 nm photolysis of ozone (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5290-5293 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photofragment excitation spectra for O(1D) production from the 317–327 nm photolysis of ozone under supersonic free-jet and low-temperature flow conditions show structure superimposed on an underlying continuum. Doppler profiles of the nascent O(1D) photofragments confirm that the O(1D) formed by photolysis at the wavelengths of the peaks in the photofragment excitation spectrum arises from the hitherto unobserved spin-forbidden predissociation to O(1D)+O2(X 3Σg−) products. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472370
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  • 9
    Electronic Resource
    Electronic Resource
    Laser photodissociation of chlorine and methyl chloride on low-temperature silicon substrates (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 792-798 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser irradiation at 193 or 351 nm of a multilayer of Cl2 or CH3Cl on an Si wafer at 100 K leads to both photodissociation of these molecules and formation of photoetching products. The kinetic energy distributions of photofragments (Cl, CH3) and etching products (SiCl, SiCl2) were measured. The kinetic energy distribution of Cl or CH3 is bimodal for the case of thin deposition of parent molecules on substrates, in which the two-component analysis of Maxwell–Boltzmann represents experimental results, assuming average kinetic energies of ∼1 and 10 kcal/mol. The etching products have kinetic energies of 1 kcal/mol. For the thick-deposition case, the kinetic energy distribution of Cl or CH3 fragments is composed of a single component with an average kinetic energy of 10 kcal/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343404
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  • 10
    Electronic Resource
    Electronic Resource
    Spatially and time-resolved detection of gallium atoms formed in the laser photochemical vapor deposition process of trimethylgallium by laser-induced fluorescence: Decomposition in the adsorbed state (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 371-374 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spatially and time-resolved detection of gallium atoms formed in the excimer-laser photochemical vapor deposition (CVD) process of trimethylgallium at 248 nm was made by the laser-induced fluorescence technique. The result shows the importance of chemically adsorbed species in the photo-CVD process. The presence of a thermally assisted effect in the photochemical decomposition was indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342489
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