Excitation of forbidden SI II fine structure transition by atomic hydrogen

Sergey A. Zapryagaev, S. I. Lavrinenko

P. F. Liao, John E. Bjorkholm

The fine-structure splitting of the $4F$ state of atomic sodium is determined using the technique of two-photon spectroscopy with a resonant intermediate state. The sensitivity of this Doppler-free technique allows observation of the electric-dipole-forbidden $3S\ensuremath{\rightarrow}4F$ two-photon transition. The $4F$ fine-structure splitting is found to be 229\ifmmode\pm\else\textpm\fi{}4 MHz. Its sign and magnitude are hydrogenic, in complete contrast to the $D$ levels of Na.

S. N. Tiwary, D. D. Singh

Sergey A. Rashkovskiy

We consider the microwave-to-optical frequency conversion based on the Lamb shift, fine structure and forbidden transitions. The theory of such a conversion is developed and the efficiency of the microwave-to-optical frequency conversion is calculated. We show that the ratio of the peak power of the induced optical emission to the power of the incident microwave, for a hydrogen atom, can reach 1000000.

W. Ewart Williams