MOLECULAR IMAGING USING FEMTOSECOND LASER PULSES

Abstract

<p>Recent technological advances have brought the possibility of directly imaging polyatomic molecular dynamics within reach. Consequently, several diffractive and non-diffractive time-resolved imaging techniques are currently under development worldwide. The work described here was motivated by the desire to pioneer the femtosecond laser-initiated Coulomb explosion approach to molecular imaging. The research project's original objective has been met using a unique instrument that can measure and correlate multiple three-dimensional ion velocities. Using this state-of-the-art machine, the first Coulomb explosion images of triatomic molecules have been produced. Furthermore, the apparatus has been employed to demonstrate that existing ultrafast laser technology is sufficient to confine virtually any molecule inertially during its multiple ionization. In conjunction with the instrument's novel capabilities, the Coulomb explosion process has been exploited in numerous other applications. For instance, a time-resolved method for directly imaging rotational wave packets in diatomic molecules has been demonstrated. Further, a high-sensitivity technique has been developed for detecting non-sequential "shake-off' double ionization in molecular deuterium. In other experiments, the optical timing of ion flight has been demonstrated, which should enable the fabrication of the world's smallest time-of-flight mass spectrometer. Finally, the instrument's excellent momentum resolution has given rise to an entirely new technique for observing molecular dynamics: electron self-diffraction imaging.</p>