OBSERVATION OF SUB-DOPPLER INFRARED SPECTRUM OF THE $H_{3}O^{+}$ ION
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Date
1987
Authors
Chen, Yit-Tsong
Oka, T.
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The frequency tunable infrared source obtained by using the microwave modulation sidebands on $CO_{2}$ laser radiation is sufficiently powerful ($5 \sim 10 mWatts$) and monochromatic $(\Delta \nu \le 20 kHz)$ to conduct systematic saturation-dip spectroscopy in the $10\mu m$ region. Recently this technique was combined with the multiple reflection mirror system to increase the $sensitivity^{1}$ so that it can be applied to molecular ion spectroscopy. We report on the first successful observation of this technique applied to the $\nu_{2}$ vibration-inversion-rotation transition of $H_{3}O^{+}$ ion. The magnetic field enhanced D.C. negative glow $discharge^{2}$ of $\sim 30$ mTorr and low current produced the best result. So far the $*Q(6.6)$ transition has been observed with the signal to noise better than 10 with linewidth of $\sim 500 kHz$ (FWHM). Using the frequency stabilized $CO_{2}$ laser allows us to measure the frequency of the $H_{3}O^{+}$ transition with an absolute accuracy of $\le 300 kHz$. The measurement of more transitions and attempts at observing rotational Zeeman effect and proton hyperfine structure are in progress.
Description
$^{1}$ Y. T. Chen, J. M. Frye and T. Oka, J. Opt. Soc. Am. B 3, 935 (1986). $^{2}$ F. C. DeLucia, E. Herbst, G. M. Plummer and G. A. Blake, J. Chem. Phys., 78, 2312 (1983).
Author Institution: Department of Chemistry and Department of Astronomy and Astrophysics, The University of Chicago
Author Institution: Department of Chemistry and Department of Astronomy and Astrophysics, The University of Chicago