Cold N+NH collisions in a magnetic trap

Area of Science:

• Atomic and molecular physics
• Quantum scattering theory
• Cold atom and molecule research

Background:

• Understanding atom-molecule interactions is crucial for controlling chemical reactions in ultracold environments.
• Nitrogen atoms (N) and nitrogen hydride molecules (NH) are key species in astrochemistry and plasma physics.

Purpose of the Study:

• To experimentally and theoretically investigate the collision dynamics of N atoms with NH molecules at ultracold temperatures.
• To determine the loss rate coefficient and identify the dominant interaction mechanisms governing these collisions.

Main Methods:

• Experimental: Trapping of N atoms and NH molecules in a mixture at ~600 mK and measuring trap loss rates.
• Theoretical: Performing accurate quantum scattering calculations using ab initio interaction potentials.

Main Results:

• A small N+NH trap loss rate coefficient of k(loss)(N+NH)=9(5)(3)×10⁻¹³ cm³s⁻¹ was measured.
• Quantum scattering calculations agreed well with experimental data.
• The magnetic dipole interaction was identified as the primary mechanism responsible for atom-molecule loss.
• The ratio of elastic-to-inelastic collisions was found to remain large (>100) even at millikelvin temperatures.

Conclusions:

• The study provides crucial insights into the low-temperature collision dynamics of N+NH systems.
• The dominance of magnetic dipole interaction suggests pathways for controlling reactivity in ultracold N/NH mixtures.
• The high elastic-to-inelastic collision ratio indicates potential for sympathetic cooling and Bose-Einstein condensate formation.