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  • 1
    Electronic Resource
    Electronic Resource
    Hydrated Electron Reactions in View of Their Temperature Dependence (1967)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 89 (1967), S. 1263-1264 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00981a041
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  • 2
    Electronic Resource
    Electronic Resource
    Photodissociation dynamics of jet-cooled ClNO on S1(1 1A‘): An experimental study (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1107-1115 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report measurements of photofragment yield (PHOFRY) spectra and NO E, V, R distributions following dissociation of jet-cooled ClNO on the S1(1 1A‘) electronic surface. The dissociative S1(1 1A‘)←S0(1 1A') transition shows diffuse vibrational structure with a progression in ν1, the NO stretch. The absorption and PHOFRY spectra consist of two bands, corresponding to excitations into S1(000) and S1(100), whose widths are 1300±100 and 1000±70 cm−1, respectively. The relative partial absorption cross sections are S1(000):S1(100)=2.3:1.0. The narrowing of the absorption bands with increasing ν1 quanta is a consequence of the mismatch between ν1 and the free NO vibrational frequency. Dissociations on S1(000) and S1(100) yield NO in v‘=0 and 1, respectively. The NO(X2∏) rotational distributions in v‘=0 and 1 are inverted, peaking at J‘∼30.5 with widths of 10±1 J‘, and they do not vary significantly when the photolysis laser is scanned across the absorption band. The evolution of NO vibrational and rotational excitations appear to be largely uncoupled. In NO v‘=0 and 1, the upper spin–orbit state 2∏3/2 is more populated than the lower state 2∏1/2. For both v‘=0 and 1, the Λ-doublet ∏(A‘) component of NO(2∏1/2) is more populated than the ∏(A') component by a ratio of ∼3:1, as expected for excitation to a π* orbital of a‘ symmetry, but this propensity is much lower for NO(2∏3/2), possibly due to perturbations with another surface. The absorption spectra and NO V, R distributions are in good agreement with recent dynamical calculations on a three-dimensional (3-D) potential-energy surface (PES) calculated ab initio. The vibrational distribution appears to be determined near the Franck–Condon (FC) region, while final-state interactions affect the rotational distributions at larger Cl–NO separations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459174
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  • 3
    Electronic Resource
    Electronic Resource
    Correlated product state distributions in the unimolecular reaction of NCNO (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 209-218 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Following excitation to S1, expansion-cooled NCNO undergoes nonradiative couplings to S0 and predissociates to CN and NO. Doppler profiles of selected CN B 2Σ+←X 2Σ+ rotational lines were recorded using LIF at several excess energies between 0 and 3000 cm−1. This yields NO V,R distributions associated with specific CN(X 2Σ+) rotational states. The profiles can be fit using the statistical PST/SSE model, and the correlated distributions show no evidence of dynamical bias or exit channel barriers. Doppler profiles generated with polarized lasers show little or no spatial anisotropy of recoil velocities, and are fit by anisotropy parameters β∼0, even at excess energies where predicted unimolecular lifetimes are ≤1 ps. Possible causes for the lack of spatial anisotropy are discussed. Analyses of NO fragment LIF spectra obtained at excess energies of 2348 and 2875 cm−1 show a slight preference for the Π(A') Λ-doublet component for J‘≥30.5, suggesting planar dissociation. An in-plane orientation of the singly occupied pπ lobe in NO is to be expected for dissociation on the ground (A') electronic potential energy surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456523
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  • 4
    Electronic Resource
    Electronic Resource
    NO(X 2Π) product state distributions in molecule–surface collision-induced dissociation: Direct inelastic scattering of n,i-C3F7NO from MgO(100) at Eincident≤7.0 eV (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2330-2345 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecule–surface collision-induced dissociation (CID) has been studied for n-C3F7NO and i-C3F7NO molecular beams scattered from MgO(100) at incident kinetic energies (Eincident) up to 7 eV. The NO fragment was detected state selectively using two-photon, two-frequency ionization, and rotational and spin–orbit distributions are reported for several Eincident values. State and angle-resolved signals were integrated to give CID yields, which increased sharply with Eincident . In most cases, rotational excitation could be described by separate temperatures for each spin–orbit state. The upper 2∏3/2 state was underpopulated relative to statistical predictions (e.g., for n-C3F7NO at Eincident =5.0 eV, the spin–orbit temperature was ∼170 K, while Trot was ∼500 K). The CID results are compared to NO state distributions derived from the photodissociation of expansion-cooled molecules under collision-free conditions, at different energies (E°) above D0. These distributions were measured for both n-C3F7NO and i-C3F7NO up to E°∼4500 cm−1, and rotational excitation within each spin–orbit state was statistical, except at E°≥3000 cm−1. As with CID, a low [2∏3/2]/[2∏1/2] ratio was observed, and the reaction mechanism is probably unimolecular decomposition via the lowest triplet surface T1 with little or no exit channel barrier. The pronounced similarities between the CID and photodissociation results suggest that common reaction mechanisms may be operative. All of the CID results are compatible with direct inelastic scattering followed by unimolecular reaction on the S0 and/or T1 potential surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459905
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  • 5
    Electronic Resource
    Electronic Resource
    State-selective photodissociation dynamics of NOCl: The influence of excited state bending and stretching vibrations (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6547-6548 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation of jet-cooled NOCl following excitation in the lowest, structured absorption band is reported. We find that NO(2∏3/2) is produced preferentially, and that the rotational distributions depend strongly on the number of bending quanta in the upper electronic state. In addition, the NO vibrational excitation depends on parent NO stretch excitation. NO(v‘=0) is predominantly produced when v'1 =0 is excited, while NO(v‘=1) is mainly formed following excitation of v1 =1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455374
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  • 6
    Electronic Resource
    Electronic Resource
    Ab initio calculations of dissociative electronic states of ClCN: Implications to the photodissociation dynamics of the cyanogen halides (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 331-340 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio configuration interaction calculations with full geometric optimization along the Cl–CN dissociation coordinate have been carried out for several electronic states of ClCN. The calculations treat all low-lying singlet and triplet states and yield the vertical transition probabilities and oscillator strengths, as well as angular dependences near the Franck–Condon (FC) region and least energy paths for several electronic states as a function of rCCl. We find that the low-lying excited states derive from three electronic configurations: π3σ*, π3π*, and σπ4σ*. The lowest excited triplet and singlet states derive from the π3σ* configuration and give rise to bent 1,3A' and 1,3A‘ states. States arising from the π3π* configuration are linear (Σ and Δ states). There is evidence of surface crossings along the reaction coordinate between triplet states arising from the π3π* configuration and those arising from the π3σ* and σπ4σ* configurations. These crossings can be induced by slight bending of ClCN causing lowering of the symmetry. The calculated vertical excitation energies are in good agreement with features of the absorption spectrum, and suggest that the A continuum of ClCN involves transitions to the 2 1A' and 1 1A‘ states. The implications to the photodissociation dynamics of the cyanogen halides are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460347
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  • 7
    Electronic Resource
    Electronic Resource
    The influence of excited-state vibrations on fragment state distributions: The photodissociation of NOCl on T1(1 3A‘) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4296-4307 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: NO V,R distributions are reported following photodissociation of jet-cooled NOCl from selected vibrational levels of the T1(1 3A‘) state. By varying the photolysis wavelength while monitoring selected rovibrational levels of NO, a photofragment yield spectrum showing the same diffuse vibrational structure as the absorption spectrum is obtained. NO rotational distributions are obtained at photolysis wavelengths corresponding to peaks in the absorption spectrum. We find that the NO stretching vibrations of T1 evolve adiabatically into NO vibrational excitations [i.e., excitation of v1 quanta of the T1 NO stretch yields predominantly NO(v‘=v1) ]. The NO rotational distributions depend only on the number of T1 bending quanta, v3. The shapes of the distributions reflect the number of nodes in the bending wave functions, and similar rotational distributions are obtained following excitation of vibronic levels with equal number of ν3 quanta, but different number of ν1 quanta (v1=0–2).We also find that the excited NO(2Π3/2) state is much more populated than the lower NO(2Π1/2) state, and the widths of the absorption features increase with increasing number of ν3 quanta, but decrease with increasing ν1 excitation. The results are explained in terms of a model in which the bending and NO stretch motions in the excited state are largely uncoupled. In order to explain the multimodal rotational distributions, we calculate separately the components of the NO rotational excitation that derive from the angular momentum inherent in the bending wave function and the angular anisotropy in the potential-energy surface. We find, using the momentum representation of the harmonic oscillator, that the rotational distributions map the bending wave functions and exhibit minima for v3〉0. In addition, a unidirectional torque generated by the angular anisotropy in the potential causes shifts in the distributions calculated by the pure Franck–Condon model that are bending level dependent. The observation that the absorption linewidth decreases with increasing NO stretch excitation in the parent T1 state may be a manifestation of the energy mismatch between the frequency of the NO stretch in NOCl and free NO; the increased mismatch with increasing stretch quantum number results in slower dissociation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457789
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  • 8
    Electronic Resource
    Electronic Resource
    Molecule–surface dissociative scattering of n-C3F7NO from MgO(100) at hyperthermal energies: Nascent NO (X 2Π) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3883-3885 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The title reaction was examined for incident kinetic energies in the range 3–7 eV and surface temperatures in the range 500–800 K; dissociation probabilities as high as 3±1% were measured. NO state distributions were obtained near the specular angle using two-photon, two-frequency laser ionization, and spin–orbit "temperatures''∼170 K were observed, in contrast to higher rotational excitations. Possible mechanisms are mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455798
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  • 9
    Electronic Resource
    Electronic Resource
    The electronic spectrum of NOCl: Photofragment spectroscopy, vector correlations, and ab initio calculations (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3903-3914 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic absorption spectrum of NOCl in the region 620–180 nm is assigned by using vector properties of the NO photofragment and the results of ab initio calculations at the CI level. In assigning the electronic spectrum, we take into account the recoil anisotropy, rotational alignment, and Λ-doublet populations of NO, as well as the calculated vertical excitation energies, oscillator strengths, and the nature of the orbitals involved in the transitions. In the experiments, we use expansion-cooled samples and measure the recoil anisotropy parameters from the Doppler profiles of selected NO A 2Σ+←X 2Π rotational lines. The alignment parameters and Λ-doublet populations are derived from the rotational spectra using different laser polarizations and excitation–detection geometries. The theoretical calculations treat all low-lying singlet and triplet states. The calculations yield least energy paths for the excited states, with optimized rNO and ClNO angle as a function of rClN, as well as the angular dependences of the potentials and oscillator strengths of the singlet–singlet transitions. The following assignments are proposed for the main absorption bands: (1) E band—T1(1 3A‘)←S0(1 1A'); the transition borrows intensity by mixing with remote singlet states, predominantly the 4 1A' state; (2) D and C bands—S1(1 1A‘)←S0(1 1A'); the C band corresponds to excitation of ν'1 in S1; (3) B band—S3(2 1A')←S0(1 1A'); (4) A band—S5(4 1A')→S0(1 1A'). The assignments proposed here are in full agreement with all the experimental observations and the results of the calculations. Despite the shallow minima calculated for the T1 and S1 surfaces, dissociation on all the surfaces is fast, and the implications of the results to the dissociation dynamics are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455801
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  • 10
    Electronic Resource
    Electronic Resource
    A nomenclature for Λ-doublet levels in rotating linear molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1749-1753 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is proposed that the two Λ-doublet levels of linear molecules with nonzero electronic orbital angular momentum be labeled Λ(A') and Λ(A‘), e.g., Π(A') and Π(A‘) for Π states, etc., according to the following prescription: All series of levels in which the electronic wave function at high J is symmetric with reflection of the spatial coordinates of the electrons in the plane of rotation will be designated Λ(A') for all values of J, and all those for which the electronic wave function is antisymmetric with respect to reflection will be denoted Λ(A‘). It is emphasized that this notation is meant to supplement, and not replace, the accepted spectroscopic e/f labeling and the parity quantum number. The utility of the Λ(A')/Λ(A‘) notation is that it is of most relevance in the mechanistic interpretation of reactive or photodissociative processes involving open-shell molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455121
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