P.-M. Hillenbrand,
K. N. Lyashchenko,
S. Hagmann,
O. Andreev,
D. Banaś,
E. P. Benis,
I. Bondarev,
C. Brandau,
E. De Filippo,
O. Forstner,
J. Glorius,
R. E. Grisenti,
A. Gumberidze,
D. L. Guo,
M. O. Herdrich,
M. Lestinsky,
Y. Litvinov,
V. Pagano,
N. Petridis,
M. S. Sanjari,
D. Schury,
U. Spillmann,
S. Trotsenko,
M. Vockert,
A. B. Voitkiv,
G. Weber,
and T. Stoehlker

Phys. Rev. A,

**Electron-loss-to-continuum cusp in collisions of U89+ with N-2 and Xe**Phys. Rev. A,

**104**:012809 (July 2021)## Abstract:

We study the electron-loss-to-continuum (ELC) cusp experimentally and theoretically by comparing the ionization of U89+ projectiles in collisions with N-2 and Xe targets, at a beam energy of 75.91 MeV/u. The coincidence measurement between the singly ionized projectile and the energy of the emitted electron is used to compare the shape of the ELC cusp at weak and strong perturbations. A significant energy shift for the centroid of the electron cusp is observed for the heavy target of Xe as compared to the light target of N-2. Our results provide a stringent test for fully relativistic calculations of double-differential cross sections performed in the first-order approximation and in the continuum-distorted-wave approach.