PLASMA DIAGNOSIS USING INFARED SPECTROSCOPY: ANOMALOUSLY HIGH POPULATION OF THE $v=3$ LEVEL AND DOUBLING OF $ArH^{+}$ SPECTRAL LINES DUE TO DOPPLER SHIFT IN AN AC DISCHARGE
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Date
1986
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Ohio State University
Abstract
Among the molecular ions so far studied, $ArH^{+}$ is special in that its abundance in discharges is very high and that highly excited vibration-rotation states are populated (1,2). We have observed two anomalous effects in high J(R(20)-R(24)) rotational spectrum of $ArH^{+}$ for five vibrational states $(v=0-4)$. (A) The rotational spectral line corresponding to $v=3$ vibrational state is stronger than the lines in other vibrational states under certain discharge conditions with high Ar pressure, while spectral lines for other vibrational states are approximately thermal. Our observation indicates that $ArH^{+}$ is initially produced in the $v=3$ state after the ion-molecule reaction and that its vibrational relaxation is slow. (B) We have observed splitting of spectral lines due to AC Doppler effect which gives directly the ion velocity and then the ion mobility in the discharge(3). Observation and analysis of these results will be presented.
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(1) J. W. Brault and S. P. Davis, Physica Scripta 25, 268 (1982) (2) J. W. C. Johns, J. Mol. Spectrosc, 106, 124 (1984) (3) N. N. Haese, F. S. Pan and T. Oka, Phys. Rev. Lett. 50, 1575 (1983) Address of authors: Department of Chemistry and Astronomy \& Astrophysics, the University of Chicago, Chicago, 1L 60637.
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