Angle-resolved line profiles in the predissociation of D2 : A summation of Fano and Lorentzian profiles

Abstract

Fano profiles usually refer to the line profiles due to the total photon absorption cross sections. In this work, we measured the angle-resolved line profiles of the $\mathrm{D}(2s,2p)$ fragments from the predissociation of ${\mathrm{D}}_{2}$ near the second threshold using the D-atom Rydberg tagging time-of-flight method. The line profiles of the fragments recoiling at the parallel and perpendicular directions to the polarization direction of the excitation laser were found to be significantly different from each other, as well as with the Fano profiles of total absorption cross sections. Based on the previous theoretical results, we found that the angle-resolved line profiles can be expressed as a summation of Fano and Lorentzian profiles. Using the formula and the previously determined parameters from the so-called \ensuremath{\beta} profiles, we calculated the angle-resolved line profiles, which are in good agreement with the experimental data. Anisotropy parameters arising from the interferences between the continuum and discrete states were found to play a role in the angle-resolved line profiles.