15min:

YUKIO HOSAKI AND KENTAROU KAWAGUCHI, Faculty of Science, Okayama University, Okayama 700-8530, Japan; SVATOPLUK CIVIS, J. Heyrovsky Institute of Physical Chemistry, Academy of Science of the Czech Republic, Dolejskova 3, 18223 Prague 8, Czech Republic.

The He₂ molecule is known to have many electronic transitions between Rydberg states in visible and ultraviolet regions. However, in infrared region only two bands b³ _g - a³ _u⁺ and B¹ _g - A¹ _u⁺ have been studied by using a DC discharge method so far. Recently we developed a time resolved Fourier transform spectroscopy with high resolution Bruker IFS 120 HR by using micro controller SX. In the present study, the FT system was applied to infrared emission spectroscopy of He₂ which was produced by a pulsed discharge in He with pulse width of 20 µsec and 1 A peak-to-peak current. In the 1800-10000 cm^-1 region, many electronic transitions have been observed in addition to the previously reported two bands. From observed time profiles of emission spectra, Rydberg states with higher energy than the b state are produced efficiently in afterglow plasma after termination of the discharge.

A least-squares analysis was carried out for the h³ _u⁺ - g³ _g⁺ and g³ _g⁺ - d³ _u⁺ bands in the 3200 cm^-1 region to determine the molecular constants. A transition from an un-identified state to the d³ _u⁺ state has been observed with irregular P- and R- branch intensities.