Recombination and cascade of Rydberg antihydrogen

Abstract

We present the results of a computational study of the recombination and cascade of antihydrogen into its ground state. We use a full time-dependent theory for recombination and compare the results with those predicted by (quasi-) time-independent theories. We introduce a stochastic interpretation of the recombination process and use it to explore the dependence of the recombination coefficient on plasma temperature and density. We use the time-dependent approach, introduced here, to explore the effect of a stimulating laser field on the recombination process.

Rydberg-atom formation in strongly correlated ultracold plasmas

“…Performing classical trajectory Monte-Carlo (CTMC) simulations of isolated three-body collisions and using rate equations they confirmed the T − 9 2scaling of the recombination rate and calculated the corresponding proportionality constant. Subsequent studies based on CTMC calculations or rate equations [23,[51][52][53] have since confirmed the strong temperature dependence, which was found to be in good agreement with experiments in hot and cold (T > 10000 K) plasmas [51,52,54] as well as with measurements on UCPs with moderate coupling strength (Γ 0.2) [22,23].…”

“…Generally, the recombination rate ν is defined as the rate at which ground state atoms are populated in the plasma [51,53,62,89]. While such deeply bound states defy a classical description, it was shown in [49] that this rate can also be determined from the downward energy flux through a kinetic bottleneck energy that divides weakly bound from stable atomic states.…”

“…For ideal plasmas (Γ → 0) and within the adiabatic treatment of Bates, Kingston, and McWhirter [89], the ionization probability P ion (E b = −R/n 2 ) can be directly obtained from the collision rates eqs. (9)-(12) [53,90] (16) by summing over the probabilities of all possible pathways in energy space that connect an atomic level of binding energy E b = −R/n 2 to the continuum, where A(n) = nmax n =n R(n, n ) + R ion (n) is the total rate for leaving level n. The first term in eq. (16) represents the probability that the bound electron will be ionized directly from level n. The second term accounts for an intermediate step via a level n from which subsequent ionization occurs, and so on.…”

Collisional-radiative recombination Ar++eDohnal1, Roučka2, Jusko3 et al. 2011Phys. Rev. A

“…A similar process, in which energy is transferred to neutral atoms, is less efficient by many orders of magnitude and can be ignored in plasmas at low neutral densities. CRR is important in many discharge and astrophysical plasmas, in ultracold plasmas, but also as a crucial step in the formation of antihydrogen in antiprotonpositron plasmas [1][2][3][4].…”

“…At the temperatures and the electron densities used in this study, the first term accounts for more than 90% of the total CRR recombination. A simpler approximate ternary recombination rate coefficient K CRR = α CRR /n e ∼ = 3.8 × 10 −9 T −4.5 e cm 6 s −1 (2) can then be defined, which is strongly dependent on temperature, but independent on n e . Very recently, Pohl et al [10] have published improved calculations of the electron-impactinduced transitions between excited Rydberg states.…”