Dissociative ionization and post-ionization alignment of aligned O in an intense femtosecond laser field.

We examined dissociative ionization of O in an intense femtosecond laser field (782 nm, 120 fs, 4 × 10 W cm) by recording the kinetic energy distribution of O emitted along the laser polarization direction as a function of the delay time between the pump pulse (9 × 10 W cm) for the molecular alignment and the probe pulse for the dissociative ionization. We found the two distinct rotational revival patterns which are out-of-phase by π with each other in the kinetic energy distribution of O. One of the patterns shows the dissociative ionization is enhanced when the O axis is parallel to the laser polarization direction, suggesting that the ionization is induced by the electron emission from the 3σ orbital.

Single and sequential double ionization of NO radical in intense laser fields.

We examine the dependences of the single and double ionization probabilities of NO radical on the angle between the NO axis and the laser polarization direction in an intense laser field (790 nm, 100 fs, 1-10 × 10 W/cm) and show that the double ionization is enhanced when the NO axis is parallel to the laser polarization direction. We reveal that the angular dependence of the sequential double ionization probability is determined by the shape of the 5σ orbital of NO from which the second photoelectron is emitted in the ionization from NO to NO. We also reveal that the fast oscillation in the probability of the tunnel ionization of NO originating from a coherent superposition of the two spin-orbit components in the electronic ground XΠ state is described well based on the molecular Ammosov-Delone-Krainov (MO-ADK) theory in which the time evolution of the electron density distribution of the 2π orbital is taken into account.

Rotational dynamics and transitions between Λ-type doubling of NO induced by an intense two-color laser field.

We numerically investigate the rotational dynamics of NO in the electronic ground XΠ state induced by an intense two-color laser field (10 TW/cm) as a function of pulse duration (0.3-25 ps). In the short pulse duration of less than 12 ps, rotational Raman excitation is effectively induced and results in molecular orientation.

Absolute carrier-envelope-phase dependences of single and double ionization of methanol in a near-IR few-cycle laser field.

We investigate the carrier-envelope phase (CEP) dependences of the single and double ionization processes of methanol (CHOH) in an intense near-IR few-cycle laser field (2.1 × 10 W/cm) by the asymmetry in the ejection direction of CH for the non-hydrogen migration channels and CH for the hydrogen migration channels created through the C-O bond breaking after the ionization. Based on the absolute CEP values at the laser-molecule interaction point, calibrated by the method using intense few-cycle circularly polarized laser pulses [Fukahori et al.