  Self-focusing of a cw laser beam in rubidium atomic vapor was studied. The
beam power and beam spot size at entrance of a glass cell with the rubidium
vapor were variable parameters. A steep grow of the threshold power of
self-focusing for the small beam radii (< 30 {\mu}m) was observed. Our
experimental data are in an agreement with the theoretical results published by
Semak and Shneider in 2013. Additional experiments in resonance and transparent
media are suggested in order to check and extend our measurements.
