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Relaxation dynamics in a molecular ultracold plasma : control and modeling Wang, Ruoxi


In many-body systems out-of-equilibrium, strong coupling triggers emergent properties that can act to limit the natural dissipation of energy and matter. The physics of strong coupling plays an important but incompletely understood role in the dynamics of natural plasmas over a wide range of length scales. Particularly remarkable signs of hindered transport appear under laboratory conditions in the self-organized avalanche, bifurcation, and quench of the nitric oxide molecular ultracold plasma. Here, a UV-UV double-resonant excitation of nitric oxide, cooled to 500 mK in a skimmed supersonic molecular beam prepares an ellipsoidal Rydberg gas of known initial density in a single selected state of principal quantum number, n₀. Penning ionization, followed by an avalanche of electron-Rydberg collisions, forms a plasma of NO⁺ ions and weakly bound electrons, in which a residual population of n₀ Rydberg molecules evolves to a state of high orbital angular momentum, ℓ. A 60 MHz radio frequency pulse with a peak-to-peak amplitude as low as 400 mV/cm, applied to a plasma in a state of arrested relaxation, depletes the residual Rydberg signal. Similarly, mm-wave fields in the range from 70 to 100 GHz tuned to resonance with n₀f (2)→(n₀ ±1)d(2) transitions deplete the plasma signal to an amplitude near zero. We associate both effects with Rydberg electronic orbital angular momentum redistribution. New theoretical work has developed a primitive picture of this system using a Lindblad master equation to describe the Markovian dynamics that arise when a closed quantum system of disordered, randomly interacting molecular dipoles couples to a thermal continuum of free atoms.

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