Direct inelastic scattering of N sub 2 from Ag(111). IV. Scattering from high temperature surface

Journal Article · Wed Nov 01 04:00:00 EST 1989 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.457532· OSTI ID:5287423

Kummel, A C; Sitz, G O; Zare, R N ^[1]; Tully, J C ^[2]

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1. Department of Chemistry, Stanford University, Stanford, California 94305 (US)
2. AT T Bell Laboratories, 1D-346, Murray Hill, New Jersey 07974

We have measured the rotational state distribution and the angular momentum alignment and orientation of N{sub 2} scattered from Ag(111) at 540 K. Using resonance enhanced multiphoton ionization (REMPI), we are able to probe the scattered flux as a function of the exit angle {theta}{sub exit}. For a modestly glancing incident beam ({theta}{sub {ital i}} =30{degree}) and incident translational energy, {ital E}{sub {ital i}} =0.3 eV, the angular momentum alignment (tumbling vs helicoptering) at both quasispecular detection ({theta}{sub exit}=35{degree}) and superspecular detection ({theta}{sub exit}=50{degree}) is only weakly dependent upon the surface temperature. However, the angular momentum orientation (clockwise vs counterclockwise rotation) is strongly affected by the surface temperature. Raising the surface temperature from {ital T}{sub {ital s}} =90 K to {ital T}{sub {ital s}} =540 K causes the orientation to decrease substantially. Stochastic trajectory calculations were carried out in conjunction with the experiments. They reveal that at low temperature there is an averaging over two important initial conditions: the two-dimensional impact parameter and the molecular orientation geometry. At high temperature there is also an averaging over the instantaneous positions and momenta of the surface atoms. Hence, a given two-dimensional impact parameter and molecular orientation geometry results in a greater range of final {ital J} states, angular momentum polarizations, and velocities (exit angles) at high temperature than at low temperature. The resulting smearing'' accounts for the changes in rotational state distribution and polarization as a function of exit angle observed at high temperature.

• OSTI ID: 5287423
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 91:9; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ALIGNMENT
ANGULAR MOMENTUM
BEAMS
COLLISIONS
DISTRIBUTION
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
HIGH TEMPERATURE
IONIZATION
METALS
MOLECULAR BEAMS
MOLECULE COLLISIONS
MULTI-PHOTON PROCESSES
NITROGEN
NONMETALS
ORIENTATION
PHOTOIONIZATION
ROTATIONAL STATES
SILVER
SURFACES
TRANSITION ELEMENTS