Hyperfine structure, isotopic level shifts, and pressure self-broadening of the $7 {}^{2}P$ states of natural thallium by Doppler-free two-photon absorption

The hyperfine constants, isotopic level shifts, and a pressure self-broadening constant of the

7 {}^{2}P

states of

{}^{203, 205}{Tl}

have been measured by the Doppler-free two-photon absorption technique. The hyperfine constant of the

7 {}^{2}P_{\frac{3}{2}}

state is found to be greater than that of the

6 {}^{2}P_{\frac{3}{2}}

state. This anomaly is tentatively attributed to a sign change in the promoted core

S

-electron spin-polarization contribution to the hfs as calculated by Fermi and Segrè for the

6 {}^{2}P_{\frac{3}{2}}

state. The isotope shift of the

7 {}^{2}P_{\frac{1}{2}}

state is 20% smaller than that of the

7 {}^{2}P_{\frac{3}{2}}

state, confirming the nuclear volume effect of the

p_{\frac{1}{2}}

electron. At higher pressures line broadening is observed as the Tl density is increased.

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Hyperfine structure, isotopic level shifts, and pressure self-broadening of the7P2states of natural thallium by Doppler-free two-photon absorption