Double resonance studies of hydroxyl radical complexes with hydrogen and nitrogen.

Format:

Book

Thesis/Dissertation

Author/Creator:

Schwartz, Rebecca Lynn.

Contributor:

Lester, Marsha I., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Chemistry, Physical and theoretical.

0494.

Penn dissertations--Chemistry.

Chemistry--Penn dissertations.

Local Subjects:

Penn dissertations--Chemistry.

Chemistry--Penn dissertations.

0494.

Physical Description:

158 pages

Contained In:

Dissertation Abstracts International 58-07B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

The interaction of OH (X $\sp2\Pi$, A $\sp2\Sigma\sp+$) with hydrogen and nitrogen has been characterized through spectroscopic means. Laser-induced fluorescence (LIF) and fluorescence depletion (FD) experiments have been used to probe the intermolecular vibrational levels supported by the OH A $\sp2\Sigma\sp+$ + H$\sb2$/D$\sb2$ and OH A $\sp2\Sigma\sp+$ + N$\sb2$ potentials. Additionally, infrared spectroscopy has been implemented to characterize the OH X $\sp2\Pi$ + H$\sb2$ potential.

Most of the intermolecular vibrational levels correlating to OH A $\sp2\Sigma\sp+$ (v$\sp\prime$ = 0) + H$\sb2$/D$\sb2$ have been accessed via FD. LIF experiments reveal a turn on of fluorescence at the OH A $\sp2\Sigma\sp+$ (v$\sp\prime$ = 0) + H$\sb2$/D$\sb2$ dissociation limits, enabling the determination of the ground state binding energies, 54 cm$\sp{-1}$ and 66 cm$\sp{-1},$ and a lower limit on the excited state binding energies, 631 cm$\sp{-1}$ and 705 cm$\sp{-1},$ respectively. The energies of these levels have been compared with predictions from ab initio theory. Homogeneous line broadening in the FD spectra suggests that electronic quenching and/or reaction are occurring on the picosecond time scale.

FD has been used to probe many of the intermolecular vibrational levels supported by the OH A $\sp2\Sigma\sp+$ (v$\sp\prime$ = 0) + N$\sb2$ potential. OH-N$\sb2$ complexes prepared in these levels have picosecond lifetimes due to electronic quenching. An onset of fluorescence at the OH A $\sp2\Sigma\sp+$ (v$\sp\prime$ = 0) + N$\sb2$ dissociation limit has been observed enabling the determination of the ground and excited electronic state binding energies at $\sim$250 cm$\sp{-1}$ and $\ge$1372 cm$\sp{-1},$ respectively. Both FD and LIF have been implemented to study OH-N$\sb2$ complexes in the OH A $\sp2\Sigma\sp+ -$ X$\sp2\Pi$ 1-0 region; these complexes have lifetimes of $\sim$200 fs. A lower limit on the binding energy of this potential is 1511 cm$\sp{-1}.$

An infrared-ultraviolet FD technique has been used to observe the rotationally-resolved infrared overtone spectrum of OH-H$\sb2$ near the OH X $\sp2\Pi$ 2 $\gets$ 0 origin. A comparison with ab initio theory confirms that the spectrum is due to ortho-H$\sb2$-OH. The lack of homogeneous line broadening in the spectrum indicates quenching and/or reaction are occurring slower than 45 ps. The magnitudes of the depletions suggest that these processes are taking place on the nanosecond time scale.

Notes:

Thesis (Ph.D. in Chemistry) -- University of Pennsylvania, 1997.

Source: Dissertation Abstracts International, Volume: 58-07, Section: B, page: 3660.

Supervisor: Marsha I. Lester.

Local Notes:

School code: 0175.

ISBN:

9780591501698

Access Restriction:

Restricted for use by site license.