Time-Resolved Photoelectron Spectra of ${\mathrm{CS}}_2$: Dynamics at Conical Intersections

We report results of the application of a fully ab initio approach for simulating time-resolved molecular-frame photoelectron angular distributions around conical intersections in ${\mathrm{CS}}_2$. The technique employs wave packet densities obtained with the multiple spawning method in conjunction with geometry- and energy-dependent photoionization matrix elements. The robust agreement of these results with measured molecular-frame photoelectron angular distributions for ${\mathrm{CS}}_2$ demonstrates that this technique can successfully elucidate, and disentangle, the underlying nuclear and photoionization dynamics around conical intersections in polyatomic molecules.

Figure 1

Potentials for the lowest few ${}^1{A}^{\prime }$ states of neutral ${\mathrm{CS}}_2$ along the C–S antisymmetric stretch coordinate for bond angles of (a) 180°, (b) 160°, and (c) 140° with the other C–S bond length fixed at 3.0 a.u. Each color curve represents (a) a diabatic state and (b),(c) an adiabatic state.

Figure 2

(a) Measured MFPADs with error bars (blue bars) and their best fit (blue curves) at time delays of 100 fs (left) and 500 fs (right), and calculated MFPADs convoluted by a Gaussian function with a standard deviation of 15 deg (red) at time delays of 106 fs (left) and 493 fs (right), (b) calculated MFPADs (red) and their contributions from the $S_2$ state (green) and $S_3$ state (light blue) at 106 and 493 fs, and (c) the density of the nuclear wave packet on the adiabatic $S_2$ and $S_3$ states at 106 and 493 fs. The (blue) banded region in (c) corresponds to the region producing 0.15 eV electrons for $r_2$ fixed at 3 a.u.