MILLIMETER-WAVE SPECTROSCOPY AND GLOBAL ANALYSIS OF THE LOWEST EIGHT VIBRATIONAL STATES OF DEUTERATED HYDRAZOIC ACID (DN3)

Amberger, Brent K.

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Description

Title

MILLIMETER-WAVE SPECTROSCOPY AND GLOBAL ANALYSIS OF THE LOWEST EIGHT VIBRATIONAL STATES OF DEUTERATED HYDRAZOIC ACID (DN3)

Author(s)

Amberger, Brent K.

Contributor(s)

• McMahon, Robert J.
• Esselman, Brian J.
• Woods, R. Claude

Issue Date

26-Jun-15

Keyword(s)

Small molecules

Abstract

Hydrazoic acid (chem{HN_3}) and chem{DN_3} have qualitatively different rotational spectra, owing in large part to a substantial difference in their emph{A} rotational constants (345 GHz for chem{DN_3} emph{vs} 611 GHz for chem{HN_3}). Like chem{HN_3}, chem{DN_3} has six fundamental vibrational modes, of which four are visible in our millimeter-wave spectra at room temperature. Between 240 and 450 GHz, many pure rotational transitions for the ground vibrational state, nub{5} (496 cm$^{-1}$), nub{6} (586 cm$^{-1}$), nub{4} (955 cm$^{-1}$), nub{3} (1197 cm$^{-1}$), the first overtones of nub{5} and nub{6}, and the combination nub{5}+nub{6} have been observed and assigned. Because chem{DN_3} is a light molecule, the rotational energy levels are widely spaced, leading to numerous interactions between rotational states of different vibrational modes. We have drawn on a wealth of previously published ro-vibrational data from high resolution FTIR spectrafootnote{J. Bendtsen and F. M. Nicolaisen, emph{J. Mol. Spectrosc.} textbf{125}, 14 (1987)}$^{,}$footnote{J. Bendtsen, F. Hegelund and F. M. Nicolaisen, emph{J. Mol. Spectrosc.} textbf{128}, 309 (1988)}$^{,}$footnote{J. Bendtsen and F. M. Nicolaisen, emph{J. Mol. Spectrosc.} textbf{145}, 123 (1991)}$^{,}$footnote{C. S. Hansen, J. Bendtsen and F. M. Nicolaisen, emph{J. Mol. Spectrosc.} textbf{175}, 239 (1996)} in our efforts to understand these perturbations. The centrifugal distortion interaction between nub{5} and the ground state of chem{DN_3} is less dramatic than in chem{HN_3} but still significant. chem{DN_3} shows the same set of Coriolis interactions as does chem{HN_3}, but again, their magnitude is generally smaller. In chem{DN_3} the nub{4} state is at slightly lower energy than 2nub{5}, instead of being nearly degenerate with nub{5}+nub{6} as is the case for chem{HN_3}. Therefore, there are strong local interactions between 2nub{5} and nub{4}, as well as between nub{3} and 2nub{6}. A notable advantage in solving the chem{DN_3} problem compared to chem{HN_3} is the substantial increase in the number and diversity of observable emph{b}-type lines in our frequency region. Furthermore, the smaller emph{A} value permits higher emph{K} states to be observed due to a more gradual decrease in state populations. Ground state observations have been extended through emph{K} = 11 and through emph{J} = 50. Pickett's SPFIT has been employed to carry out multi-state fits using combined datasets of our millimeter-wave data and the published FTIR data.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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