Multichannel Quantum Defect Theory for cold molecular collisions

Multichannel Quantum Defect Theory (MQDT) is shown to be capable of producing quantitatively accurate results for low-energy atom-molecule scattering calculations. With a suitable choice of reference potential and short-range matching distance, it is possible to define a matrix that encapsulates the short-range collision dynamics and is only weakly dependent on energy and magnetic field. Once this has been produced, calculations at additional energies and fields can be performed at a computational cost that is proportional to the number of channels N and not to N^3. MQDT thus provides a promising method for carrying out low-energy molecular scattering calculations on systems where full exploration of the energy- and field-dependence is currently impractical

Stereodynamical control of a quantum scattering resonance in cold molecular collisions

Cold collisions of light molecules are often dominated by a single partial wave resonance. For the rotational quenching of HDandnbsp;(vandnbsp;=andnbsp;1,andnbsp;jandnbsp;=andnbsp;2) by collisions with ground stateandnbsp;para-H2, the process is dominated by a singleandnbsp;Landnbsp;=andnbsp;2 partial wave resonance centered around 0.1andnbsp;K. Here, we show that this resonance can be switched on or off simply by appropriate alignment of the HD rotational angular momentum relative to the initial velocity vector, thereby enabling complete control of the collision outcome.</p

Stereodynamical control of a quantum scattering resonance in cold molecular collisions

Cold collisions of light molecules are often dominated by a single partial wave resonance. For the rotational quenching of HD (v = 1, j = 2) by collisions with ground state para-H2, the process is dominated by a single L = 2 partial wave resonance centered around 0.1 K. Here, we show that this resonance can be switched on or off simply by appropriate alignment of the HD rotational angular momentum relative to the initial velocity vector, thereby enabling complete control of the collision outcome.</p