2015, Ferré, A., Boguslavskiy, A.E., Dagan, M., Blanchet, V., Bruner, B.D., Burgy, F., Camper, A., Descamps, D., Fabre, B., Fedorov, N., Gaudin, J., Geoffroy, G., Mikosch, J., Patchkovskii, S., Petit, S., Ruchon, T., Soifer, H., Staedter, D., Wilkinson, I., Stolow, A., Dudovich, N., Mairesse, Y.

High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20-26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected.

2013, Shafir, D., Soifer, H., Bruner, B.D., Dagan, M., Mairesse, Y., Patchkovskii, S., Ivanov, M.Y., Smirnova, O., Dudovich, N.

We probe the dynamics of tunnel ionization via high harmonic generation. We characterize the ionization dynamics in helium atoms, and apply our approach to resolve subtle differences in ionization from different orbitals of a CO 2 molecule.