FIG. 2.

(a) Relevant potential energy surfaces of formamide (chemical structure displayed in (c)) along the out-of-plane bending normal coordinate q initiated by the pump pulse and displayed in (d). The calculated potentials for the ground state, the first valence excitation, and the C, N, and O K-edges are shown. q = 0 is the planar achiral geometry, and the two minima at ±0.6q correspond to the two enantiomers. The geometries (a), (b), and (c) displayed in Fig. 1 are indicated in (a). In the pump-probe scheme sketched in (b), a left polarized NUV pump creates a valence excitation, and the molecule then evolves in the excited state double well potential, and is then probed after a delay τ by the circularly polarized X-ray light at various K-edges (C, N, and O). The difference between the left and right probe absorption gives the chiral contribution to the signal.