INFRARED EMISSION SPECTRUM OF $He_{2}$ OBSERVED BY A PULSED DISCHARGE
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Date
2003
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Ohio State University
Abstract
The $He_{2}$ molecule is known to have many electronic transitions between Rydberg states in visible and ultraviolet regions. However, in infrared region only two bands $b^{3}\Pi_{g} - a^{3}\Sigma^{+}_{u}$ and $B^{1}\Pi_{g} - A^{1}\Sigma^{+}_{u}$ 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 $SX^{a}$. In the present study, the FT system was applied to infrared emission spectroscopy of $He_{2}$ which was produced by a pulsed discharge in He with pulse width of $20 \mu$sec 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 $h^{3}\Sigma^{+}_{u} - g^{3}\Sigma^{+}_{g}$ and $g^{3}\Sigma^{+}_{g} - d^{3}\Sigma^{+}_{u}$ bands in the $3200 cm^{-1}$ region to determine the molecular constants. A transition from an un-identified state to the $d^{3}\Sigma^{+}_{u}$ state has been observed with irregular P- and R- branch intensities.
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$^{a}$K. Kawaguchi, O. Baskakov, Y. Hosaki, Y. Hama, and C. Kugimiya, Chem. Phys. Lett. 369, 293(2003)
Author Institution: Faculty of Science, Okayama University; J. Heyrovsky Institute of Physical Chemistry, Academy of Science of the Czech Republic
Author Institution: Faculty of Science, Okayama University; J. Heyrovsky Institute of Physical Chemistry, Academy of Science of the Czech Republic