Product-state distribution after isotopic substitution in ultracold atom-molecule collisions

We show that products of the isotopic substitution reactions in experimentally accessible molecules such as NaK, RbCs, and SrF are cold according to their translational energy below hundreds of mK. For these chemical reactions, molecular products may occupy only the lowest rotational states. We also discuss the possibility of controlling the chemical reactions by the electric field in ultracold mixtures of molecules and atoms with low kinetic energy release, where one of the constituent atoms of colliding molecule is replaced by its isotope. This letter opens new avenues in investigating the branching ratios of chemical reactions in ultracold conditions

Quasi-classical trajectories study of Ne2Br2(B) vibrational predissociation: Kinetics and product distributions

The vibrational predissociation of the Ne2Br2(B) van der Waals complex has been investigated using the quasi-classical trajectory method (QCT), in the range of vibrational levels v' = 16-23. Extensive comparison is made with the most recent experimental observations [Pio et al., J. Chem. Phys. 133, 014305 (2010)], molecular dynamics with quantum transitions (MDQT) simulations [Miguel et al., Faraday Discuss. 118, 257 (2001)], and preliminary results from 24-dimensional Cartesian coupled coherent state (CCCS) calculations. A sequential mechanism is found to accurately describe the theoretical dynamical evolution of intermediate and final product populations, and both QCT and CCCS provide very good estimates for the dissociation lifetimes. The capabilities of QCT in the description of the fragmentation kinetics is analyzed in detail by using reduced-dimensionality models of the complexes and concepts from phase-space transport theory. The problem of fast decoupling of the different coherent states in CCCS simulations, resulting from the high dimensionality of phase space, is tackled using a re-expansion scheme. QCT ro-vibrational product state distributions are reported. Due to the weakness of the vdW couplings and the low density of vibrational states, QCT predicts a larger than observed propensity for \Delta v' = -1 and -2 channels for the respective dissociation of the first and second Ne atoms.Comment: 16 pages, 6 figures, 4 tables. Accepted for publication in J. Chem. Phy

Dipolar Collisions of Ultracold Ground-state Bosonic Molecules

The dipolar collision between ultracold polar molecules is an important topic both by its own right from the fundamental point of view and for the successful exploration of many-body physics with strong and long-range dipolar interactions. Here, we report the investigation of collisions between ultracold ground-state sodium-rubidium molecules in electric fields with induced electric dipole moments as large as 0.7$\;$D. We observe a step-wise enhancement of losses due to the coupling between different partial waves induced by the increasingly stronger anisotropic dipolar interactions. Varying the temperature of our sample, we find good agreement with theoretical loss rates assuming complex formation as the main loss process. Our results shed new light on the understanding of complex molecular collisions in the presence of strong dipolar interactions and also demonstrate the versatility of modifying molecular interactions with electric fields.Comment: 8 pages, 4 figures, PRX in pres