Non-Born–Oppenheimer study of the muonic molecule ion 4He μ+
Yang Hang1, 2, Wu Meng-Shan1, †, Zhang Yi1, 2, Shi Ting-Yun1, Varga Kalman3, Zhang Jun-Yi1
       

Probability density distributions of ρ(rα–μ+) and ρ(rα–e) for the (j = 0,ν = 0,1,2) states. In panel (b), ρ(rα–e) for 4He is also shown.