Strong field driven electric currents in condensed matter systems open new frontiers in petahertz electronics. In this regime new challenges arise as the role of the band structure and the quantum nature of electron-hole dynamics have yet to be resolved. Here we reveal the underlying attosecond dynamics that dictates the temporal evolution of carriers in multi-band solid state systems, via high harmonic generation (HHG) spectroscopy. We demonstrate that when the electron-hole relative velocity approaches zero, enhanced quantum interference leads to the appearance of spectral caustics in the HHG spectrum. Introducing the role of the dynamical joint density of states (JDOS) we identify its direct mapping into the spectrum, exhibiting singularities at the spectral caustics. By probing these singularities, we visualize the structure of multiple unpopulated high conduction bands. Our results open a new path in the control and study of attosecond quasi-particle interactions within the field dressed band structure of crystals.Induced by the strong field interaction, HHG provides a unique spectroscopic scheme to visualize the coherent evolution of petahertz currents inside solids.Since the first observation [1], solid HHG opened a door into the study of the electronic structure and dynamics in crystals [2,3,4,5,6,7], multiple band dynamics [8,9,10,11] and complex many-body phenomena [12] in crystalline and amorphous systems [9]. For a moderate field strength the electron-hole dynamics are often described semi-classicaly by a single valence and conduction band of

The 193 nm photodissociation of individual rotational levels of HOD molecules excited with one quantum of O–H or O–D stretching vibrational energy is described. Stimulated Raman excitation and coherent anti-Stokes Raman scattering are used to prepare and detect, respectively, the (0,0,1) (O–H stretch) or (1,0,0) (O–D stretch) vibrationally excited HOD. The OD and OH fragments are detected by laser-induced fluorescence. In the photodissociation of HOD (0,0,1), the yield of both fragments is enhanced [relative to HOD (0,0,0)], but the yield of OD is increased 2.5±0.5 times more than that of OH. In the photodissociation of HOD (1,0,0), no enhancement of the yield of the fragments is obtained. Our results show that even the very lowest possible level of vibrational excitation can be ‘‘leveraged’’ to effect selective bond breaking. Also, these results demonstrate that bond cleavage does not necessarily occur on the weakened bond and they agree with theoretical calculations indicating that the yield of OD and OH fragments depends on the Franck–Condon overlap of the vibrational wave function with the repulsive surface of the upper state.

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