Observation of the P-wave Shape Resonance

TL;DR

This paper reports the first experimental observation of a P-wave shape resonance in low-temperature Penning ionization collisions, revealing detailed insights into intermolecular interactions and quantum scattering phenomena.

Contribution

It presents the first observation of a P-wave resonance in Penning ionization, demonstrating sensitivity to van der Waals interactions and probing higher angular momentum states.

Findings

Observation of P-wave resonance at 22 mK energy

Resonance sensitivity to van der Waals potential

Detection of shape resonance at angular momentum l=6

Abstract

Partial wave resonances are quasi-bound states that are formed by tunneling through the centrifugal barrier. Such states are important to collisions that deviate from the Langevin limit where direct collision path is suppressed due to quantum symmetry or a potential barrier. In such a case, quantum resonances play a major role in the dynamics at low temperatures where scattering process can be described mainly by the resonance contribution. Here we present the first observation of the lowest-lying partial wave resonance in the Penning ionization collisions between metastable neon and rovibrationally ground state HD molecules. We observe the resonance at an energy of $k_B\times$22mK taking advantage of the phase space correlation similar to atomic delta kick cooling. We show that the $p$-wave resonance position is particularly sensitive to the leading term of the van der Waals interaction. We also measure shape resonance at a higher angular momentum state, $l=6$, allowing us to disentangle and probe the short and the long parts of the intermolecular interaction.