Accession Number : ADA317972

Title :   Spectroscopic Studies of the Gas-Phase ArCH(D) Complexes: I. Detection and Analysis of B-X Electronic Transitions of ArCH by Laser-Induced Fluorescence.

Descriptive Note : Final rept. Jan 93-Jan 95,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : McQuaid, M. J. ; Sausa, R. C. ; Lemire, G. W. ; Kotlar, A. J.

PDF Url : ADA317972

Report Date : NOV 1996

Pagination or Media Count : 40

Abstract : Gas-phase argon-methylidyne (ArCH) van der Waals (vdW) complexes have been detected spectroscopically by laser-induced fluorescence (LIF) near CH B(2)sigma - X(2) Pi sub r (0,0) and (1,0) transitions. They are formed in a supersonic free-jet expansion of argon seeded with CH radicals generated by the 248-nm photolysis of CHBr2Cl. The LIF spectra reveal a number of rovibronic bands that are assigned to stretching and/or bending motions of the ArCH complex. From the spectra, lower limits for the ground and excited state binding energies are estimated. Analysis of the rotational energy level structure based on combination differences and computer simulations of eight of the rovibronic bands yields an average ground state value of B'av = 0.174 + or - 0.004 /cm and excited state constants ranging from B' = 0.086 - 0.116 /cm. This indicates that the ArCH vdW bond is lengthened considerably upon electronic excitation. A splitting of the ground state rotational energy levels is observed that is related to the nature of the intermolecular potential and Coriolis coupling. Based on the rovibronic structure of the ArCH bands and a hindered internal rotational model describing the interaction of Ar((1)S o) atom with a CH monomer, a linear equilibrium geometry is inferred for the excited state and a T-shaped geometry for the ground state.

Descriptors :   *SPECTROSCOPY, *LASER INDUCED FLUORESCENCE, *GASES, *ELECTRONS, *ENERGY LEVELS, *ARGON, COMPUTERIZED SIMULATION, COUPLING(INTERACTION), COMPLEX COMPOUNDS, DETECTION, MODELS, PHOTOLYSIS, EXCITATION, MOTION, ATOMS, BENDING, PHASE, NUCLEAR BINDING ENERGY, LOW LEVEL, GEOMETRY, GROUND STATE, MOLECULE MOLECULE INTERACTIONS, SUPERSONIC FLOW, ROTATION, VAN DER WAALS FORCES, CORIOLIS EFFECT.

Subject Categories : Inorganic Chemistry
      Organic Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE