Molecular Dynamics in Diatomic Molecules with One- and Two-Color Ultrafast Laser Pulses

Strong field ionization with ultrafast laser pulses allows for real-time measurements of the forming and breaking of chemical bonds. The time duration of an ultrafast pulse is tens of femtoseconds while dynamics such as nuclear vibration and dissociation occurring in small molecules is hundreds of fs. Ultrafast lasers are therefore capable of imaging these dynamics in real-time, providing insight into the physics of molecular ionization, vibration, and orbital structure. I will discuss several experiments examining the effects of strong field ionization in diatomic iodine in the presence of a two-­color (800­ and 400 nm) phase stable femtosecond laser pulse. By controlling the relative phase of the two-color pulse, the magnitude and direction of the electric field can be controlled. As strong field ionization depends exponentially on the electric field strength, ionization rates can be controlled. The spatial asymmetry of the pulse breaks the spatial symmetry of ionization allowing for control over directions of ion yields while providing insight into the physics of ionization. We find a critical region in which there is spatially asymmetric enhanced ionization of the (2,0) channel to a counterintuitive (1,2) channel. I will also discuss the development of a velocity map imaging (VMI) detector which provides two-dimensional information about the dissociation and distribution of molecular ions upon ionization. The VMI along with Fourier transform spectroscopy allows us to identify specific molecular orbitals from which electrons are removed through ionization by measuring the vibrational period and angular distributions of the ion fragments