FOURIER-TRANSFORM SPECTROSCOPY OF $^{14}$NH$_3$ AND $^{15}$NH$_3$ IN THE NEAR-INFRARED
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Date
2006
Journal Title
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Volume Title
Publisher
Ohio State University
Abstract
The near-infrared absorption spectrum of NH$_3$ is an interesting opportunity for atmospheric {\it in-situ} measurements of this species using tuneable diode-lasers. For this purpose, accurate line positions and intensities are indispensable. In the past, several studies of the absorption spectrum of $^{14}$NH$_3$ in the near-infrared were carried out, using Fourier-transform$^{1}$ and tuneable diode-laser spectroscopy.$^{2-4}$ More recently, high-resolution diode-laser spectra of $^{15}$NH$_3$ were analyzed for the first time.$^{5}$ The lines of $^{14}$NH$_3$ in this region are also useful for wavenumber calibration of absorption spectra obtained with tuneable lasers. In our group, we have recently investigated the possibility to detect atmospheric NH$_3$ using photoacoustic laser spectroscopy in the 1.5 $\mu$m region, and observed several discrepancies between individual line positions and intensities observed in our and previous studies$^{1,4}$, as already noticed by other groups.$^{2,5}$ In order to solve this problem we have measured new absorption spectra of $^{14}$NH$_3$ (and also of $^{15}$NH$_3$) in the 6300-7500 cm$^{-1}$ region using a Bruker IFS 120-HR Fourier-transform spectrometer. The length of the absorption cell was 30 cm. The NH$_3$ pressures employed were around 30 mbar, and the spectral resolution used was 0.02 cm$^{-1}$, leading to linewidths (Full-Width at Half-Maximum) of about 0.03 cm$^{-1}$. Based on these spectra, we have produced a list of individual line positions and line intensities at 296 K. Comparisons with the previous studies$^{1-5}$ will be presented. }, {\bf 162}, 230-245 (1993).} }, {\bf 40}, 2031-2042 (2004).} }, {\bf 45}, 31-45 (2004).} }, {\bf 28}, 59-66 (2004).} }, in press (2006).}
Description
Author Institution: Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA), CNRS and Universites Paris-7 et -12, Creteil, France; Laboratorio de Espectroscopia e Laser, Instituto de Fisica, Universidade Federal Fluminense, Niteroi, Rio de Janeiro, Brazil