Acquisition and analysis of complex spectra in the ultraviolet. Large amplitude motion as a probe of acid-base chemistry in the gas phase
A new CW laser/molecule beam spectrometer has been constructed. The high resolving power of this instrument (2 parts in 10[sup 8]) makes it possible to observe the fully resolved electronic spectra of large molecules in the ultraviolet, using fluorescence excitation techniques. The molecules discussed in this thesis include 1- and 2-hydroxynaphthalene (1/2HN) and the hydrogen bonded complexes of 2HN with ammonia, 2HNA. From analyses of their spectra, the authors deduce structural and dynamical information about 1/2HN and 2HNA in their ground (S[sub o]) and first excited singlet (S[sub 1]) states. A low resolution jet study of the S[sub 1] [l arrow] S[sub o] fluorescence excitation spectra (FES) of 1HN and 2HN reveals the existence of two electronic origins of each isomer, one associated with a cis (or syn) and one with a trans (or anti) geometry with respect to the naphthalene frame. The rotational constants of the zero-point vibrational levels (ZPL) of 1/2HN and the hydroxy deuterated 1/2HN (1/2DN) have been measured to an accuracy of [+-]0.1 MHz. From these data, the authors determine the center of mass coordinates of the hydroxy hydrogen atoms in both the S[sub o] and S[sub 1] states to an accuracy of [+-]0.02 [angstrom]. These coordinates make possible an unambiguous assignment of the two electronic origins to the specific rotamers, cis and trans. S[sub 1] [l arrow] S[sub o] transition moment angles have been measured to an accuracy of [+-]5[degrees]. These are found to be significantly different for each rotamer. While significant differences in the hydrogen atom coordinates are observed for the cis and trans rotamers, no differences are observed between the S[sub o] and S[sub 1] coordinates in either rotamer. Photoexcitation of 1/2HN to S[sub 1] is known to significantly enhance their acid properties. In order to probe this property directly, high resolution FES of 2HN hydrogen bonded to the Broensted base ammonia have been obtained.
- Research Organization:
- Pittsburgh Univ., PA (United States)
- OSTI ID:
- 7070060
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMMONIA
MOLECULAR STRUCTURE
ULTRAVIOLET SPECTRA
COMPLEXES
NAPHTHALENE
ELECTRON SPECTRA
ELECTRONIC STRUCTURE
EXCITED STATES
AROMATICS
CONDENSED AROMATICS
ENERGY LEVELS
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
SPECTRA
400201* - Chemical & Physicochemical Properties