Relaxation effects in photoionization time delay near the 3s Cooper minimum of Ar

The discrepancy in the attosecond time delay between theory and experiment near the 3s Cooper minimum (CM) of Ar [1] is addressed. It is found that inclusion of the relaxation effects in the time delay difference between Ar 3s and 3p photoionization near the 3s CM dramatically alters the 3s time delay and brings the theory into substantial agreement with experiment using the relativistic random phase approximation [2] with relaxation [3]. The key point is that 3s photoionization is dominated by interchannel coupling in this region and the interchannel coupling matrix elements were found to be considerably altered by the inclusion of relaxation. This implies that relaxation should be important for any atomic or molecular transition that is dominated by interchannel coupling. [1] C. Alexandridi et al., Phys. Rev. Research 3, L012012 (2021). [2] W. R. Johnson and C. D. Lin, Phys. Rev. A 20, 964 (1979). [3] V. Radojević, M. Kutzner and H. P. Kelly, Phys. Rev. A 40, 727 (1989).