Abstract
The rotation of molecules in the gas phase is coherently excited by irradiation with strong nonresonant
short laser pulses, interacting with the molecular anisotropic polarizability. The coherent rotational
excitation has been attracting much attention because of the intriguing nature of the rotational wave
packet thus created, and its wide applicability to dynamical studies and advanced optics. Here, we
describe an approach based on a quantum-state resolved spectroscopic probe for investigating coherent
rotational excitation by intense nonresonant laser fields. Representative examples are given to show how
the method provides detailed information on excitation pathways in wave-packet creation, and how it
realizes full quantum-state reconstruction of the rotational wave packet in a favorable case. We also
describe an advanced wave-packet control, i.e., the creation and characterization of a unidirectionally
rotating wave packet, and discuss a further extension of the present approach to explore coherent
vibrational excitation.
