Knowledge Bank

The absorption spectrum of lithium, sodium and potassium in neon, argon, krypton and xenon matrices in the region from 2000 to 8000 {\AA} has been studied as a function of temperature and, at $4\circ K$, as a function of concentration. The first member of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}P\leftarrow 2S$ series can be observed in all matrices. Higher members are weak and can in most matrices not be assigned. At alkali concentrations $\ge 0.1$%, strong additional absorptions are observed which seem to be due to diatomics or higher aggregations. Most transitions appear blue shifted. The $P1/2$ and $P3/2$ components of lithium are not resolved. Sodium shows a greatly increased doublet splitting and in potassium a strong triplet is observed. The spectra are sharp in xenon but become increasingly diffuse when lighter rare gas host matrices are chosen. The line shape indicates partially resolved or unresolved fine structure in most absorption features. During the warm up the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}P\leftarrow 2S$ absorption broadens and shifts to the red. For a given ratio of observation temperature to melting point of host lattice, atomic absorption of the alkali metals seems to have the same line width in all of the observed matrices. The present observations will be compared with earlier literature on Na in $Ar1$ and with results on Hg in rare gas $matrices.2$