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
       

The average interparticle distances (in units of a.u.) for all bound states of 4He μ+.