Apparent change of the 3C/3D line intensity ratio in neonlike ions

The resonance 3 C ([(2 p 5 ) 1/2 3 d 3/2 ] J =1 → [2 p 6 ] J =0 ) to intercombination 3 D ([(2 p 5 ) 3/2 3 d 5/2 ] J =1 → [2 p 6 ] J =0 ) line intensity ratio of neonlike ions has been studied. The measured line intensity ratio for neonlike Xe 44+ ions shows an apparent change, which is reproduced by the calculations using the relativistic configuration interaction plus many-body perturbation theory. It is clearly elucidated that the change in the 3 C /3 D line intensity ratio is caused by strong configuration mixing between the upper levels of the 3 D and 3 F ([(2 p 5 ) 1/2 3 s ] J =1 → [2 p 6 ] J =0 ) lines. The present measurement allows us to discuss the 3 C /3 D line intensity ratio for the highest- Z ions hitherto, which suggests that the experiment-theory discrepancy in the 3 C /3 D line intensity ratio of neonlike ions diminishes with increasing atomic number Z and further trends to vanish at higher- Z ions. Furthermore, the present study provides benefits to better understand configuration mixing effect in the radiative opacity of hot plasmas.