The Absorption Spectrum of Lead Vapor in the Ultraviolet

Absorption spectrum of lead vapor, 5000 to 2000A.—Using a column of vapor about 3 cm long in a carbon tube at various temperatures up to 1600°C, absorption was found at 34 lead lines, of which 20 are new. The results may be interpreted very well on the basis of the energy diagram given by Thorsen and Grotrian. Absorptions were observed only from the normal state $2p_4$ and the metastable states $2p_3$ and $2p_2$. The introduction of the $2p_5$ state does not seem to be necessary. Additional combinations have been found with the terms $X_1$ and $X_2$. A new term $X_3$ (10232) is proposed. Values are suggested for the terms $3p_2$, $3p_3$, $4p_2$, $4p_3$. Evidence is given for interchanging the terms $3d_1$ and $3d_2$ and for a new series ($2p_3-mx$).