L-changing through very-long-range interactions in collisions between high-n, n$=$300, n$^{\mathrm{1}}$F$_{\mathrm{3}}$ strontium Rydberg atoms.

Studies of state-changing in collisions between high-$n$ Rydberg atoms are analyzed. While close collisions result in ionization of an atom, even at large distances the dipole-dipole interaction generates an effective electric field at each atom triggering Stark precession and L-changing which is examined using both classical and quantum theory. The theoretical predictions are tested experimentally using high-$n$ n$^{\mathrm{1}}$F$_{\mathrm{3\thinspace }}$strontium atoms and the results show that, even for impact parameters as large as 40 $\mu $m, collisions can lead to rapid L-changing, highlighting the long-range nature of the interactions responsible.