Attosecond charge migration is a periodic evolution of the charge density at specific sites of a molecule on a time scale defined by the energy intervals between the electronic states involved. Here, we report the observation of charge migration in neutral silane (SiH 4 ) in 690 as, its decoherence within 15 fs, and its revival after 40-50 fs, using X-ray attosecond transient absorption spectroscopy. We observe the migration of charge as pairs of quantum beats with a characteristic spectral phase in the transient spectrum, in agreement with theory. The decay and revival of the degree of electronic coherence is found to be a result of both adiabatic and non-adiabatic dynamics in the populated Rydberg and valence states. The experimental results are supported by fully quantum-mechanical ab-initio calculations that include both electronic and nuclear dynamics, which additionally support the experimental evidence that conical intersections can mediate the transfer of electronic coherence from an initial superposition state to another one involving a different lower-lying state.

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The attosecond quantum beat of an electronic state superposition was captured in SiH4 using soft-X-Ray attosecond transient-absorption spectroscopy. Its decoher-ence and revival, induced by non-adiabatic vibrational dynamics, were reproduced using MCTDH calculations.

Attosecond charge migration is a periodic evolution of the charge density of a molecule on a time scale defined by the energy intervals between the electronic states involved.Here, we report the observation of charge migration in neutral silane (SiH 4 ) in 690 as, its decoherence within 15 fs, and its revival after 40-50 fs using X-ray attosecond transient absorption spectroscopy. The migration of charge is observed as pairs of quantum beats with a characteristic spectral phase in the transient spectrum.The decay and revival of the degree of electronic coherence is found to be a result of both adiabatic and non-adiabatic dynamics in the populated Rydberg and valence states. The experimental results are supported by fully quantum-mechanical abinitio calculations that include both electronic and nuclear dynamics. We find that conical intersections can mediate the transfer of electronic coherence from an initial superposition state to another one involving a different lower-lying state. Operating on neutral molecules, our methods define a general approach to the key phenomena underlying attochemistry.

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