Influence of large permanent dipoles on molecular orbital tomography

Channel-closing effects of electronic excitation in solids

We investigate the electronic excitation of solids in strong fields by solving the time-dependent Schrödinger equation. The excitation probability exhibits a strong modulation as a function of laser intensity when the initial states fill in the whole valence band. To have a clear insight into the modulation, we further study the electronic excitation from a single eigenstate in solids. A series of resonance-like enhancements of excitation probability are produced by changing the laser intensity and wavelength. We attribute the resonance-like enhancements to the channel-closing effects in solids. It is shown that the excitation probability exhibits enhancements when the value of channel is odd for intracycle interference and an integer for intercycle interference. This is different from the atom that the enhancement occur in the integer channels. We also reveal that the channel-closing effects can be observed by solid high-order harmonic generation.

Anomalous circular dichroism in high harmonic generation of stereoisomers with two chiral centers

When a molecule has more than one chiral center, it can be either a chiral molecule or a meso isomer. High harmonic generation (HHG) of stereoisomers with two chiral centers driven by circularly polarized (CP) laser pulses is investigated. Counterintuitively, it is found that the HHG exhibits prominent circular dichroism for the meso isomer, while the harmonic spectra with left and right CP laser pulses are nearly the same for the chiral isomers. We show that the anomalous circular dichroism is attributed to the characteristic recollision dynamics of HHG. This feature makes the HHG a promising tool to discriminate the meso isomer and racemic mixture, where no optical activity can be found in both cases. Similar dichroism responses are also found by applying the counter-rotating bicircular laser pulses.

Molecular photoelectron holography by an attosecond XUV pulse in a strong infrared laser field

We have investigated the photoelectron spectra from ionization of diatomic molecules by an attosecond XUV pulse in a strong infrared laser field by quantum calculations. A clear holographic interference structure is observed in the two-dimensional photoelectron momentum spectrum. Moreover, this holographic structure depends sensitively on the electron orbitals and internuclear distance of diatomic molecules. Based on the orbital dependence of the holographic structure, one can identify the symmetries and electron density distributions of molecular orbitals. This indicates that the photoelectron holography by an attosecond XUV pulse in a strong infrared field can be used as an efficient tool for molecular imaging.