Knowledge Bank

The absorption spectrum of calcium vapor has been studied at 2300 K using a King furnance. With increasing temperature the 4227 \AA resonance line of atomic Ca broadens markedly to the red and under high resolution the region from 4600 \AA to 6000 \AA shows a complex many-line spectrum. Rotational analysis confirms the spectrum as due to a $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ --- $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ transition of diatomic calcium. The situation is analogous to that already observed for $magnesium,1$ where the transition is from a very lightly bonded ground state to a more stable excited state. The rotational and vibrational structure of the $Ca2$ spectrum will be discussed, and calculations of the Franck-Condon effect in the $Mg2$ spectrum will be reported.