On the formation and decay of a molecular ultracold plasma

Abstract

Double-resonant photoexcitation of nitric oxide in a molecular beam creates a dense ensemble of $50f(2)$ Rydberg states, which evolves to form a plasma of free electrons trapped in the potential well of an NO${}^{+}$ spacecharge. The plasma travels at the velocity of the molecular beam, and, on passing through a grounded grid, yields an electron time-of-flight signal that gauges the plasma size and quantity of trapped electrons. This plasma expands at a rate that fits with an electron temperature as low as 5 K, colder that typically observed for atomic ultracold plasmas. The recombination of molecular NO${}^{+}$ cations with electrons forms neutral molecules excited by more than twice the energy of the NO chemical bond, and the question arises whether neutral fragmentation plays a role in shaping the redistribution of energy and particle density that directs the short-time evolution from Rydberg gas to plasma. To explore this question, we adapt a coupled rate-equations model established for atomic ultracold plasmas to describe the energy-grained avalanche of electron-Rydberg and electron-ion collisions in our system. Adding channels of Rydberg predissociation and two-body, electron- cation dissociative recombination to the atomic formalism, we investigate the kinetics by which this relaxation distributes particle density and energy over Rydberg states, free electrons and neutral fragments. The results of this investigation suggest some mechanisms by which molecular fragmentation channels can affect the state of the plasma.

References in corpus (3)

• Evolution from a molecular Rydberg gas to an ultracold plasma in a seeded supersonic expansion of NO
• Experimental Realization of an Exact Solution to the Vlasov Equations for an Expanding Plasma
• On the formation and decay of a molecular ultracold plasma

Cited by in corpus (12)

• Spontaneous avalanche ionization of a strongly blockaded Rydberg gas
• Rydberg atom formation in strongly correlated ultracold plasmas
• On the formation and decay of a molecular ultracold plasma
• Possible many-body localization in a long-lived finite-temperature ultracold quasi-neutral molecular plasma
• Arrested relaxation in an isolated molecular ultracold plasma
• Dissipative dynamics of atomic and molecular Rydberg gases: Avalanche to ultracold plasma states of strong coupling
• Many-body physics with ultracold plasmas: Quenched randomness and localization
• Coupled rate-equation hydrodynamic simulation of a Rydberg gas Gaussian ellipsoid: Classical avalanche and evolution to molecular plasma
• Expansion of an ultracold Rydberg plasma
• Electron trapping in freely expanding ultracold neutral plasmas
• What is the temperature of an ultra-cold Rydberg plasma?
• Ultrafast many-body dynamics of dense Rydberg gases and ultracold plasma