Knowledge Bank

Absorption coefficients of hydrogen have been measured photoelectrically with a 2-meter vacuum monochromator using the helium continuum as background at a bandwidth of $0.25\backslash AA$. Corrections due to scattered light and pressure gradients in the cell were made; however, no correction for fluorescence was necessary. From 1030 to $845\backslash AA$, the absorption coefficient curve has many fairly weak, overlapping bands. The maximum absorption coefficient is about $20cm-1$. At wavelengths less than $845\backslash AA$, there are strong bands, and the largest k-value is approximately $1500cm-1$. In particular, the $D1\Pi u\leftarrow X1\Sigma g+$ bands of $H2$ are prominent, especially at wavelengths less than $845\backslash AA$, the 1s $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}S+2p2P$ dissociation threshold. A dissociation continuum begins near $845\backslash AA$ and extends to shorter wavelengths. The ionization continuum is observed at wavelengths shorter than the ionization threshold of $803.67\backslash AA$, and at wavelengths shorter than $720\backslash AA$ no bands are superimposed. The curve slowly decreases toward shorter wavelengths from about $300cm-1$ at $700\backslash AA$ to about $190cm-1$ at $600\backslash AA$.