Controlling and imaging the nuclear motion in small molecules with ultracold laser pulses |
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| Uwe Thumm | |
| Kansas State University, USA | |
| The sudden ionization of neutral hydrogen molecules by a short and intense pump laser pulse creates a nuclear wave packet in the molecular ion. This wave packet represents the quantum mechanical generalization of the classical internuclear motion and can be decomposed into a coherent superposition of stationary vibrational states of the hydrogen molecular ion. Based on numerical simulations, I will discuss possibilities for manipulating and imaging the bound motion and dissociation of such nuclear wave packets using a sequence of three (or more) ultra-short (6 fs) and intense (1?10**14 W/cm2) near-infrared pump, control, and probe laser pulses. I will address wave packet revivals and discuss new numerical results which show that a single control pulse - with an appropriately tuned time delay - can significantly narrow the vibrational state distribution of the wave packet. A second control pulse can further squeeze the vibrational state distribution, effectively "stopping" the wave packet. This suggests a scheme for assessing the degree at which coherent nuclear motion in small molecules can be controlled by "Raman transitions" that are induced by time-delayed control pulses: the more stationary the resulting nuclear wave function is, the more distinctly will subsequent fragmentation of the molecular ion with an intense probe pulse project its nodal structure onto the measurable kinetic energy release spectrum. |