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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 106 (1984), S. 4061-4062 
    ISSN: 1520-5126
    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 92 (1990), S. 1657-1660 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Chemiluminescent reaction H+(NO)2 →HNO*+NO was studied under single collision condition. The built-in third body much enhanced the formation of HNO*(A 1A‘) in bimolecular relatively large population in bending vibration (ν3 ) as compared with the HNO* produced from the termolecular recombination, H+NO+M. This apparent excitation in bending mode can be attributed to the smaller internal energy of HNO* produced in H+(NO)2 reaction. Higher rotational states of the (001) vibration, if formed in H+NO+M reaction, most probably suffer rapid losses to X 1A' state by internal conversion. The lower energy content of HNO* formed in H+(NO)2 reaction suppresses this internal conversion and hence the relative population of the (001) state becomes large. The reaction probability was also measured as a function of collision energy and the result indicates the absence of the reaction barrier.
    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 86 (1987), S. 1111-1117 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The van der Waals (vdW) complexes consisting of benzonitrile and various partner species were formed in a free jet and their laser-induced fluorescence (LIF) spectra were recorded. For all the species chosen as partners (Ar, Kr, N2O, CF3H, and H2O), the LIF spectra showed a red shift relative to that of benzonitrile monomer. The spectral shift increased with increasing dipole moment of the partner species owing to the large dipole–dipole interaction between the partner species and benzonitrile whose dipole moment amounts to 4.14 D. With the aid of computer simulation, the rotational contours of the LIF spectra of the benzonitrile dimer and benzonitrile–Ar complex were analyzed. The dimer was found to be in planar form with the two CN groups facing each other in an antiparallel geometry, whereas in the Ar complex the Ar atom lies over the benzene ring slightly leaning toward the CN group.
    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 94 (1991), S. 3496-3503 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dynamics of the electronically excited state of 9,9'-bianthryl (BA)–acetone complexes was studied in a free jet. The BA–acetone complexes were produced by supersonic expansion of BA/acetone/He mixtures. The laser induced fluorescence spectrum of the BA–acetone complexes showed several bands which were ascribed to the complexes containing different number of acetone molecules. The number of acetone molecules attaching to BA was determined by mass-selected resonance-enhanced multiphoton ionization (REMPI) spectra for each band. The Stokes shift and lifetime were measured for each band, i.e., for the BA–acetone complex with a specific number of "solvent'' molecules. These measurements revealed that there are two kinds of BA–acetone complexes; one giving the broad laser-induced fluorescence (LIF) spectrum and largely redshifted fluorescence, and the other yielding the structured LIF and the sharp fluorescence spectrum similar to that of bare BA. The Stokes shift and the lifetime of the former complex increased with increasing number of solvated acetone molecules, whereas those of the latter complex are insensitive to the degree of solvation. These findings can be explained in terms of the importance of both the "symmetry breaking'' and the "polar microscopic solvation'' in forming the so-called twisted intramolecular charge–transfer state.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4739-4747 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational and rotational state distribution was measured for NO produced from the reaction O(1D)+N2O→2NO via a reactant pair O(1D)⋅N2O, which, in turn, formed by the 193 nm photolysis of the N2O dimer. The dimer was generated by the supersonic expansion through a pulsed nozzle. The distribution was determined by using the laser-induced fluorescence of NO on its A–X transition. The rotational distribution was of the Boltzmann type characterized by a low temperature, 60–100 K, at each vibrational level measured. The vibrational distribution was found to be composed of the two components, one very cold and the other relatively hot. The experiment using an isotopically labeled N2O revealed that the vibrational energy was not equally distributed over two kinds of NO; the NO originally present in N2O was vibrationally cool while that formed from O(1D) and the terminal nitrogen of N2O was vibrationally hot. These results indicate that the reaction occurring is the abstraction of the terminal nitrogen by O(1D). The low rotational temperature, which sharply contrasts with the extremely high rotational excitation observed for the ordinary bimolecular reaction, can be rationalized by considering the geometrical difference in the encounter between the O(1D) atom and N2O. This fact, in turn, indicates that the product energy distribution is significantly affected by the orientation in the reactive encounter.
    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 86 (1987), S. 1118-1124 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dispersed fluorescence spectra of the van der Waals (vdW) complexes consisting of benzonitrile and various partner species were observed in a free jet following a single vibronic level (SVL) excitation. For the vdW complexes with atomic species (Kr and Ar), the fluorescence was found to come from the initially prepared state and/or from the monomer produced by vibrational predissociation. On the contrary, in the case of benzonitrile–molecule complexes (H2O, N2O, and CF3H), only the fluorescence from the relaxed vdW molecule was observed. These features are interpreted in terms of a simple general scheme of predissociation. Vibrational predissociation is considered to be a composite of the four processes: (1) radiative decay of the prepared state; (2) intracomplex vibrational energy transfer producing a relaxed vdW complex; (3) radiative decay of the relaxed vdW complex; and (4) dissociation of the relaxed vdW complex. The difference in fluorescent state between atomic and molecular vdW complexes are caused by the competition among these four processes. The relative importance among these processes is strongly dependent on the state density of the vdW modes which in turn reflects the degrees of freedom of the partner species.
    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 86 (1987), S. 5491-5499 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction O+(NO)2 was studied by use of a crossed-beam apparatus. An (NO)2 beam generated by the supersonic expansion crossed at right angles with a collimated effusive beam containing oxygen atoms which were formed by microwave discharge. The product NO@B|2 was detected by the chemiluminescence. The angular distribution of the product was measured by an angle-resolved emission detection technique. The distribution has forward and backward peaks with respect to the oxygen atom incidence and indicates the occurrence of an intermediate complex in the course of the reaction. The angular velocity distribution, as well as the onset of the chemiluminescence, indicates that the reaction exothermicity appears mostly as internal energy of NO*2 . The remaining energy flows into the product translation and rotation; the vibrational freedom of the third-body molecule is not effective as an energy absorber. The emission intensity was found to decrease with increasing relative collision energy. A sharp drop of the intensity was observed at 2 kcal/mol of collision energy, which is in good agreement with the bond energy of the NO dimer.
    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 113 (2000), S. 11109-11126 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure and excited state dynamics of jet-cooled 9,9′-bianthryl (BA) and its 1:1 van der Waals (vdW) complexes with Ne, Ar, and H2O were studied using rotational coherence spectroscopy (RCS). For a free BA molecule, the magnitude and persistence of the recurrent transient appearing in the time-correlated single photon counting (TCSPC) measurement was found to be dependent on the torsional level of BA, indicating the rotational constant changes with the torsional energy level. The RCS–TCSPC measurement of the BA–Ar and BA–H2O complexes in the S1 state showed no coherent transients. However, the pump–probe time-resolved fluorescence depletion (TRFD) detected the weak J-type transient. Those facts imply the loss of coherence in the BA vdW complexes due to the excited-state dynamics, which coincides with the analysis of the laser-induced fluorescence excitation and dispersed fluorescence spectra. The structure of the ground-state 1:1 BA complex with Ne, Ar, and H2O was determined based on the RCS transients observed in the TRFD measurement with the help of a minimum energy structure calculation using atom–atom pairwise potentials. The rapid dephasing in the excited state was demonstrated by the magic angle TRFD detection near t=0. The dominant dephasing process for the rare-gas complexes is ascribed to intramolecular vibrational energy redistribution (IVR) which is accelerated by significant coupling between the torsional vibration and the low-lying vdW vibrations. IVR process for the H2O complex accompanies the rapid conversion to the charge-transfer state, which is also responsible for the loss of excited-state coherence. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 8338-8346 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-selected differential cross sections (DCSs) have been measured for the OH radicals produced from the reactions of O(3P) with saturated hydrocarbons by utilizing Doppler-resolved polarization spectroscopy. Stereodynamics in the reactions of secondary (c-C6H12) and tertiary (i-C4H10) hydrogen atoms are discussed based on the dependences of the DCSs on the collision energy and the structure of these hydrocarbons. For the c-C6H12 reaction, the DCS of the OH(2Π3/2,v′=1,j′=3.5,A′) shows predominant intensities in the backward hemisphere with reference to the incident O(3P) atom at a mean collision energy of 〈Ecoll〉=12 kJ/mol. When the collision energy is raised to 〈Ecoll〉=33 kJ/mol, the OH radicals scattered in the forward hemisphere grow almost to match those in the backward hemisphere. The observed increase in the forward scattering implies that the collision energy makes the large impact parameter collisions contribute to the reactive scattering. At a similar collision energy of 〈Ecoll〉=31 kJ/mol the forward scattering component in the DCS of the i-C4H10 reaction does not exceed that of the c-C6H12. This shows that the cone of acceptance is not enlarged in the i-C4H10 reaction from that in the c-C6H12 reaction, as opposed to the expectation based on the height of activation barrier. The absence of the enlargement of the cone of acceptance can be attributed to a large steric hindrance caused by the three bulky methyl groups surrounding the reactive tertiary C–H bond of i-C4H10. The difference in the steric hindrance can explain the difference in the temperature-dependent pre-exponential factors of the macroscopic reaction rates between the abstraction of the secondary and tertiary C–H bonds. The collision energy dependence of the DCS as well as the internal excitation of alkyl radical products reveal that the O(3P)+alkane reactions are not always dominated by the simple rebound mechanism, which has long been believed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1752-1754 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra have been studied for clusters of 9,9'-bianthryl (BA) with acetone, diethyl ketone, and methyl–ethyl ketone. Two different kinds of clusters have been observed in clusters containing the symmetric ketones. One shows broad LIF and DF spectra which are characteristic to the polar excited state of BA. The other shows sharp LIF bands and short lifetime which indicate the absence of the electron transfer.
    Type of Medium: Electronic Resource
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