Giant modification of atomic transition probabilities induced by a magnetic field: forbidden transitions become predominant

摘要

The magnetic field-induced giant modification of probabilities for seven components of 6S_(1/2), F_g = 3 → 6P_(3/2), F_e = 5 transition of the Cs D_2 line, forbidden by selection rules, is observed experimentally for the first time. For the case of excitation with circularly polarized laser radiation, the probability of a F_g = 3, m_F=-3 → F_e = 5, m_F=-2 transition becomes the largest of 25 transitions of the F_g = 3 → F_e = 2,3,4,5 group in a wide-range magnetic field of 200-3200 G. Moreover, the modification is the largest among D_2 lines of alkali metals. A half-wave-thick cell (the length along the beam propagation axis L = 426 nm) filled with Cs has been used in order to achieve sub-Doppler resolution, which allows the large number of atomic transitions that appear in the absorption spectrum to be separated when an external magnetic field is applied. For B > 3000 G the group of seven transitions F_g = 3 → F_e=5 is completely resolved and is located at the high frequency level of F_g=3 → F_e=2,3,4 transitions. The applied theoretical model describes very well the experimental curves.