Ab initio numerical methods for attosecond molecular spectroscopy*

We present our recent advances towards the development of two original numerical methods to describe the interaction between ultra-short laser pulses and correlated molecular systems. The first method, CK-LOPT [1], uses the Complex Kohn (CK) variational approach to compute multi-photon amplitudes at the lowest-order level of perturbation theory (LOPT). It can describe molecular photoionization time delay and transient absorption spectra in relatively weak fields, when only few-photon exchanges are involved. The second method, FEDVR-TDSE, uses an hybrid Gaussian and FEDVR basis set to solve the time-dependent Schr\"{o}dinger equation (TDSE), within the same close-coupling framework employed in the CK approach, and can be applied to nonpertubative regimes as well. [1] N. Douguet, B. I. Schneider, and L. Argenti, Phys. Rev. A {\bf 98} 023403 (2018),