Rotational Dynamics of Quantum State-Selected Symmetric-Top Molecules in Nonresonant Femtosecond Laser Fields

Rotational dynamics of quantum state selected and unselected CH3I molecules in intense femtosecond laser fields has been studied. The orientation and alignment evolutions are derived from a pump-probe measurement and in good agreement with the numerical results from the time-dependent Schrodinger equation (TDSE) calculation. The different rotational transitions through nonresonant Raman process have been assigned from the Fourier analysis of the orientation and alignment revivals. These revivals are derived from a pump-probe measurement and in good agreement with the numerical results from the TDSE calculation. For the molecules in rotational state vertical bar 1, +/- 1, -/+ 1 >, the transitions can be assigned to Delta J = +/- 1, +/- 2, while for thermally populated molecules, the transitions are Delta J = +/- 2. Our results illustrate that the orientation and alignment revivals of the rotational quantum-state selected molecules give a deep insight into the rotational excitation pathways for the transition of different rotational states of molecules in ultrafast laser fields.