Spin-orbit coupling of the NaK 3Π and 3Π states: Determination of the coupling constant and observation of quantum interference effects

We have studied the mutually perturbing 3³Π_Ω=0(v = 32, J = 19) ∼ 3¹Π_Ω=1(v = 6, J = 19) levels of NaK that are coupled together by the spin-orbit interaction. We note that this coupling is nominally forbidden by the ΔΩ = 0 selection rule for spin-orbit perturbations. However 3³Π levels labeled by different values of Ω are mixed by rotational coupling; i.e. the 3³Π_Ω levels are best described by a coupling scheme intermediate between Hund’s cases (a) and (b). Thus the 3¹Π_Ω=1 level couples to the 3³Π_Ω=0 level via the small admixture of 3³Π_Ω=1 character in the latter. The 3³Π_Ω=0(v = 32, J = 19) ∼ 3¹Π_Ω=1(v = 6, J = 19) f symmetry pair is of particular interest since it appears to be very close to a 50-50 mixture of triplet and singlet character, and the splitting between these levels provides a direct measure of the 3³Π ∼ 3¹Π spin-orbit coupling constant. On the other hand, excitation spectra of the 3³Π_Ω=0(v = 32, J = 19) ∼ 3¹Π_Ω=1(v = 6, J = 19) e symmetry pair through the mixed “window” levels 1(b)³Π_Ω=0(v = 17, J = 18, 20) ∼ 2(A)¹Σ⁺(v = 18, J = 18, 20) display dramatic quantum interference effects associated with “singlet” and “triplet” excitation channels. Almost complete cancellation for populating one or the other of the two upper states is observed for excitation from the predominantly triplet members of the window level pairs.     

Li2 Autler-Townes分裂的实验观察

用光学-光学双共振激光光谱研究了 7Li2A 1Σ+u态的Autler-Townes (A-T) 分裂.一个强的耦合场 (泵浦激光)激发 7Li2A 1Σ+u v′, J′← X 1Σ+g v″, J″跃迁,诱发A 1Σ+u v′, J′能级和 X 1Σ+gv″, J″能级的A-T分裂.另一个探测激光从A 1Σ+u v′,J′能级进一步激发到4 1Σ+g态.扫描探测激光,监测4 1Σ+g态碰撞诱导紫色荧光,从而探测A 1Σ+u v′, J′能级的A-T分裂.当耦合场频率偏离共振时,激发光谱线出现双重分裂.在该实验条件下,分裂大小和泵浦激光频率偏离共振频率的失谐量成正比. 研究了A-T分裂的两条线的相对强度与泵浦、探测光的强度及缓冲气体压力的关系.