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We theoretically investigate the creation of the rotational wave packet in molecular ions upon the strong-field ionization of diatomic molecules by a femtosecond laser pulse. The rotational excitation of molecular cation is ascribed to the dependence of the strong-field ionization probability on the orientation angle of the molecular axis with respect to the laser polarization direction. By extending the molecular strong-field approximation theory, we calculate the rovibrational state distribution of the ground electronic X 1 Σ + state of NO+ after the ionization of NO in the electronic ground X 2 Π 1 / 2 state. We also show that the extent of the rotational excitation of NO+ is enhanced by the stimulated impulsive Raman processes both in neutral NO and in NO+ cation. The resultant time evolution of the rotational wave packet of NO+ is in good agreement with the delay dependent NO2+ yield recorded experimentally in our previous pump–probe study. [ABSTRACT FROM AUTHOR]

An analytical formula representing the photoelectron kinetic energy at which the ejection direction of photoelectrons generated by an intense circularly-polarized few-cycle laser pulse flips was derived and was used for determining the laser pulse duration.

We observed the dynamical evolution of the electron–nuclear wavepacket composed of the and 32Πu states of with an evolution period of 1.3 fs. We created a dissociative wavepacket of by photoionization of O2 with the irradiation of an intense attosecond pulse train (APT) in the extreme ultraviolet (XUV) wavelength region, and probed it with another XUV APT by scanning delay between the two APTs. We revealed the evolution of the electron–nuclear wavepacket by the analysis of the spectral phase in the Fourier transform of the recorded delay dependent momentum spectrum of O+. We also found the correlation between the photon energy and the released kinetic energy originating from the dissociation of Rydberg states of O2 followed by the autoionization of the fragment O atom in the Rydberg states. [ABSTRACT FROM AUTHOR]