Liu Yuzhu

Ultrafast Imaging of Electronic Relaxation in Ortho-xylene: New Features from Fragmentation-Ion Spectroscopy *

As a continuous work of tracking electronic relaxation of the S2 state in o-xylene by photoelectron imaging [Y. Liu et al., Phys. Chem. Chem. Phys. 15 (2013) 18101], we report another contribution from the view of fragment-ion spectroscopy. Three components with time constants of τ1 60 fs, τ2 = 55(±20) fs and τ3 = 6.99(±0.25) ps are observed for the only fragment-ion C6H4CH3+. The velocity map image of the fragment-ion against the delay time are also measured. Transient information about the kinetic energy of the fragment-ion and angular distribution are analyzed and discussed. New features for competing ultrafast internal conversion and intersystem crossing are obtained.

Coherent Control of Molecular Orientation by a Terahertz Few-Cycle Laser Pulse

The coherent control of molecular orientation by a terahertz few-cycle laser pulse is theoretically studied. It is demonstrated that the field-free molecular orientation results from the interference contributions between the odd and even rotational wave packet, and therefore the constructive and destructive interferences lead to the observation of the positive and negative orientations, corresponding to the positive and negative degrees. Furthermore, the enhancement or suppression of the molecular orientation can be coherently manipulated by precisely controlling the carrier-envelope phase of the terahertz few-cycle pulse.