Improved production of Br atoms near zero speed by photodissociating laser aligned Br₂ molecules

We theoretically investigated the improvement on the production rate of the decelerated bromine (Br) atoms near zero speed by photodissociating laser aligned Br₂ precursors. Adiabatic alignment of Br₂ precursors exposed to long laser pulses with duration on the order of nanoseconds was investigated by solving the time-dependent Schrödinger equation. The dynamical fragmentation of adiabatically aligned Br₂ precursors was simulated and velocity distribution of the Br atoms produced was analyzed. Our study shows that the larger the degree of the precursor alignment, 〈cos²-θ〉, the higher the production rate of the decelerated Br atoms near zero speed. For Br₂ molecules with an initial rotational temperature of ∼1 K, a 〈cos²-θ〉 value of ∼0.88 can result in an improvement factor of over ∼20 on the production rate of the decelerated Br atoms near zero speed, requiring a laser intensity of only ∼1 × 10¹² W/cm² for alignment.