Infrared-pump–x-ray-probe spectroscopy of vibrationally excited molecules

Abstract

In the present paper we propose and discuss infrared (IR) pump x-ray probe scheme for molecular studies. We illustrate advantages of the pump-probe x-ray spectroscopy by means of numerical simulations employing vibrational wave-packet dynamics. Our study focuses on theoretical description of x-ray absorption (XAS) and resonant inelastic x-ray scattering (RIXS) spectra of molecules vibrationally excited by a preceding IR field, using the dissociative 1a 2

Ultrafast dissociation features in RIXS spectra of the water molecule

“…As mentioned above, the bending mode is not excited in RIXS via the lowest core-excited state |1s À1 O 4a 1 1 i. The 2D Hamiltonian for the stretching motion reads: 4,39,40…”

TD-DFT simulations of K-edge resonant inelastic X-ray scattering within the restricted subspace approximation

“…Recent studies ranging from isolated molecules, [2][3][4][5] molecules in solution, [6][7][8][9] fluctuating networks in liquid phase 10 and to correlated materials 11,12 demonstrate its versatility. RIXS also draws substantial interest for its applicability in pump-probe spectroscopies, [13][14][15][16][17] specially in the context of modern X-ray Free Electron Laser experiments.…”

Anomalous polarization dependence in vibrationally resolved resonant inelastic x-ray scattering of H2O

“…The kinetic energy operator was represented in the position space using a fourth order numerical difference formula. All calculations were performed with a modified version of the eSP ec code used in references [1,2,12,13].…”

“…This figure displays the y and z components of d c0 (R) where the y−axis lies along the antisymmetric coordinate and the z−axis is oriented along the molecular symmetry axis. Most prominent dependence is seen for d [2,12,13]: H (1) O − − − −H (2) and H (2) O − − − −H (1) . Here it is important to notice that the C 2v symmetry of the system is preserved in quantum mechanics contrary classical mechanics where the dissociation selects only one path and breaks the symmetry.…”

“…We consider here the RIXS channel of H 2 O which induce scattering through the dissociative |1a −1 1 4a 1 1 state into the electronic ground state. It has been previously shown [2,12,13] that this RIXS channel is weakly affected by the bending mode and it is well described by considering only the coupled dynamics of the OH stretching modes. We use here the same approximation and label the ground-state vibrational levels of water |n s , n a by quantum numbers of symmetric (n s ) and antisymmetric (n a ) stretching modes.…”