Knowledge Bank

The absorption spectrum of electronically excited $H2$ is being studied in a microwave discharge using the technique of dye laser intracavity absorption. As of the submission of this abstract, 82 absorption features have been observed between 584 and 601 nm. While most of these correspond to known transitions originating in the $c\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u$ metastable state of $H2$, about 18 do not correspond to transitions assigned by $Dieke1$. The wavelengths of most of these transitions are listed as having been seen in emission, but no assignments are given. We are attempting to assign these transitions. The wavelength range studied is being extended toward both the blue and the red, and additional results will be presented. The $H2$ is excited in a 2500 MHz discharge in a resonant cavity described $previously2$. The pressure in the cavity is about 5 Torr, and the discharge power is 30 watts. No other gases are added to the discharge. The absorption path is about 1 cm long, and, under these conditions, the observed transitions are quite strong. However, signal averaging by means of a computer is used to further improve the signal to noise ratio.