HYDROGEN ABSORPTION COEFFICIENTS IN THE $580-1030 {\AA}$ A WAVELENGTH REGION

Author Institution: Air Force Cambridge Research Laboratories, L. G. Hanscom FieldAbsorption coefficients of hydrogen have been measured photoelectrically with a 2-meter vacuum monochromator using the helium continuum as background at a bandwidth of $0.25 {\AA}$. Corrections due to scattered light and pressure gradients in the cell were made; however, no correction for fluorescence was necessary. From 1030 to $845 {\AA}$, the absorption coefficient curve has many fairly weak, overlapping bands. The maximum absorption coefficient is about $20 cm^{-1}$. At wavelengths less than $845 ^{\AA}$, there are strong bands, and the largest k-value is approximately $1500 cm^{-1}$. In particular, the $D ^{1}\Pi_{u} \leftarrow X ^{1}\Sigma^{+}_{g}$ bands of $H_{2}$ are prominent, especially at wavelengths less than $845 {\AA}$, the 1s $^{2}S+2p ^{2}P$ dissociation threshold. A dissociation continuum begins near $845 {\AA}$ and extends to shorter wavelengths. The ionization continuum is observed at wavelengths shorter than the ionization threshold of $803.67 {\AA}$, and at wavelengths shorter than $720 {\AA}$ no bands are superimposed. The curve slowly decreases toward shorter wavelengths from about $300 cm^{-1}$ at $700 {\AA}$ to about $190 cm^{-1}$ at $600 {\AA}$