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Author Luckhaus, D. ♦ Scott, J. L. ♦ Fleming Crim, F.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CHEMISTRY ♦ NITROGEN COMPOUNDS ♦ PERTURBATION THEORY ♦ PHOTOLYSIS ♦ HYDROXYLAMINE ♦ VIBRATIONAL STATES ♦ FRANCK-CONDON PRINCIPLE ♦ MULTI-PHOTON PROCESSES ♦ EXCITATION ♦ ELECTRONIC STRUCTURE ♦ ABSORPTION SPECTRA
Abstract We present a detailed investigation of the photodissociation of hydroxylamine following direct single-photon and vibrationally mediated two-photon excitation below 42thinsp000 cm{sup {minus}1}. In all cases the lowest dissociation channel [NH{sub 2}({tilde X}thinsp{sup 2}B{sub 1})+OH({tilde X}thinsp{sup 2}{Pi})] dominates. Single-photon dissociation at 240 nm releases most of the excess energy (20thinsp550 cm{sup {minus}1}) into relative translation (53{percent}) and NH{sub 2} internal energy (40{percent}, mostly vibrational). OH carries little internal energy (7{percent}), most of it in the form of rotational excitation. Torsional excitation during the dissociation step leads to rotational alignment of the OH fragments and a preferential population of the {Pi}(A{sup {double_prime}}) component of the lambda doublet. Both are lost after isoenergetic two-photon excitation via O{endash}H stretching overtones of NH{sub 2}OH, also leading to higher internal excitation of the NH{sub 2} fragments ({approximately}50{percent}) at the expense of relative translation. At lower total excitation energies the relative translation takes up an increasing fraction of the total excess energy ({ge}80{percent} at 5820 cm{sup {minus}1} of excess energy). The results are discussed in terms of {ital ab initio} calculations using complete active space second-order perturbation theory with augmented triple-{zeta} basis sets for the lowest excited singlet states. One- and two-dimensional potential functions explain the OH product state distributions observed in different experiments in terms of the geometry relaxation of NH{sub 2}OH upon electronic excitation. Crossing between the lowest excitated A{sup {prime}} and A{sup {double_prime}} singlet states in the Franck{endash}Condon region leads to a barrier of {approximately}0.5 eV to dissociation in S{sub 1}, which dominates the photodissociation dynamics. {copyright} {ital 1999 American Institute of Physics.}
ISSN 00219606
Educational Use Research
Learning Resource Type Article
Publisher Date 1999-01-01
Publisher Place United States
Journal Journal of Chemical Physics
Volume Number 110
Issue Number 3


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