Exploration of the magnetic-field-induced $5s5p$³P₀–5s^{2 1}S₀ forbidden transition in bosonic Sr atom

We present experimental and theoretical studies of the effect of an external magnetic field on the $5s5p$ ³ P ₀–5s ^{2 1} S ₀ forbidden transition in the bosonic Sr atom. In our ultra-cold atomic system, the excitation fraction of the forbidden transition was measured under the circumstance of the different magnetic field strengths by using the normalized detection method. Based on the perturbation theory, we calculated the magnetic-field-induced $5s5p$ ³ P ₀–5s ^{2 1} S ₀ transition rate as a function of the magnetic field strength. Electronic matrix elements entering the calculation of the transition rate were also used to derive the theoretical excitation fraction as a function of the magnetic field strength. A good agreement was found between the experimental measurements and the calculations. This study should be helpful in evaluating the magnetic field effects on the forbidden transition rate with higher accuracy. Moreover, it can help to understand the ultra-cold atomic interaction in the external magnetic field. (paper)