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Dissertation Information for Yaling Chen

NAME:
- Yaling Chen

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2000)

ADVISORS:
- Michael C. Heaven

COMMITTEE MEMBERS:
- Joel M. Bowman
- Tianquan Lian

MPACT Status: Fully Complete

Title: The dynamics of cyanogen radical van der Waals clusters and low-energy collisions

Abstract: "The spectroscopy and predissociation dynamics of CN-Ne were investigated using a variety of laser excitation techniques. Properties of the A 2 ¦° were characterized through studies of the A-X system. Both spin-orbit components of CN( A )-Ne were subject to predissociation. The upper component (¦¸ = 1/2) was predissociated by rapid spin-orbit relaxation. The lower component (¦¸ = 3/2) was predissociated by the nonadiabatic internal conversion process, CN( A 2 ¦° 3/2 , v)-Ne [arrow right] CN( X 2 ¦² + , v + 4) + Ne. Double resonance techniques were used to simplify the spectra and establish ro-vibronic assignments. Details of the intermolecular potential energy surfaces were derived from these data.

Electronic predissociation of CN( B )-Ar n (n [approximate] 100) clusters has been examined using optical-optical double resonance techniques. Rotationally cold (T rot [approximate] 130 K) CN( A , ¦Ô = 9) fragments were detected following excitation of CN( B , ¦Ô = 0)-Ar n . An upper bound for the predissociation rate of ¦£ p < 2 ¡Á 10 6 s -1 was determined. These results are consistent with a surface-bound structure for the CN-Ar n clusters, or a sequential dissociation process that involves a surface-bound intermediate. Demonstration that free CN( A ) is produced by predissociation of CN( B )-Ar n validates a previous determination of the radiative lifetime for CN( A ) 7 ¡Ü ¦Ô ¡Ü 9 levels.

Spectra for the H 2 -CN and D 2 -CN complexes have been observed in association with the monomer B 2 ¦² + - X 2 ¦² + and A 2 ¦° - X 2 ¦² + transitions. Ground state dissociation energies of D 0 '' = 38 ¡À 1 cm -1 (H 2 -CN) and D 0 '' = 42 ¡À 1 cm -1 (D 2 -CN) were determined. Ground state complex rotational constants were determined to be 0.245 cm -1 (H 2 -CN) and 0.229 cm -1 (D 2 -CN). The abnormal isotope effect was attributed to Coriolis Coupling.

Electronic predissociation of CN( A 2 ¦°)-H 2 was examined by characterizing action spectra and product state distributions. For comparison with the predissociation data, CN( A ) + H 2 collisional energy transfer was examined at temperatures near 10K. The product state distributions resulting from collisions showed symmetry preferences that were not evident in the distributions resulting from predissociation. Qualitative differences in the predissociation and collisional transfer dynamics can be explained by considering the symmetry properties of the intermolecular potential energy surfaces, and the regions of these surfaces that are sampled by each type of event."

MPACT Scores for Yaling Chen

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-04-13 14:09:08

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