Muonic Systems Research Articles

Fusion in flight from the molecular continuum of dtμ

Fusion reaction rates for the muonic molecular system dtμ are calculated in the scattering continuum above the first break-up threshold (tμ) 1s+d, and for a few of the resonant states there embedded. In order to analyze the fusion in flight reaction (tμ) + d, the molecular wave function is obtained within (a) semiclassical, (b) adiabatic, and (c) nonadiabatic descriptions, in the energy range 0.002–10 keV. The semiclassical rates are higher than the corresponding adiabatic fusion rates, but converge towards the latter for high collision energies. In the nonadiabatic treatment, the qualitatively new structure has been obtained. The fusion rate shows an oscillatory behaviour, associated with the presence of a series of virtual states and variations of the overbarrier transmission in the tμ+d potential scattering. Furthermore, the nonadiabatic fusion rates are substantially enhanced at resonant energies near the tμ 2s threshold.

Resonances in muonic systems.

A number of resonances, shape as well as Feshbach type, have been observed in atomic systems. It is expected that similar types of resonances exist in muonic systems. Froelich and Szalewicz [Phys. Lett. A 129, 321 (1988)] carried out a calculation for td\ensuremath{\mu} and obtained two resonances, for J=0 and 1, just above the d\ensuremath{\mu} threshold. Our calculation, carried out with large basis sets and different sets of nonlinear parameters, using the complex-rotation method, shows the existence of Feshbach-type resonances below the n=2 threshold of t\ensuremath{\mu} and d\ensuremath{\mu}. Positions of these resonances are in good agreement with the results of Hara and Ishihara [Phys. Rev. A 40, 4232 (1989)]. The widths of these resonances are calculated.

Three-body resonances in t alpha micro and d alpha micro.

Resonances in muonic systems {ital t}{alpha}{mu} and {ital d}{alpha}{mu} have been predicted for {ital J}=0 and 1 using the complex-rotation method. This method has the advantage that the resonance position and total width are calculated at the same time. These resonances are found to be below the {ital n}=4 threshold of {alpha}{mu} and are of Feshbach type. They decay to {ital t}{mu}+{alpha} and {ital d}{mu}+{alpha}, and therefore could be of importance in the reactivation of {mu} from {alpha}{mu} in the fusion of {ital t} and {ital d} in the presence of a muon (muon-catalyzed fusion). The channel ({alpha}{mu}){sub {ital n}=3}+{ital t} or {ital d} could be followed by multiple scattering, resulting in stripping of the muon. This process is highly density dependent.

Deexcitation of muonic molecules by internal conversion.

Stabilization of the resonantly formed muonic molecular ion (td\ensuremath{\mu}) depends on the transition from the excited J=1 state to some lower-lying state in competition with decay through the entrance channel. The most important process leading to this transition is internal conversion (Auger effect), in which the excitation energy of the muonic system is carried away by an orbital electron. Using variational wave functions similar to those previously reported [A. K. Bhatia and R. J. Drachman, Phys. Rev. A 30, 2138 (1984)], we have now computed the matrix elements responsible for the transitions. For simplicity, we have assumed that the muonic ion is the nucleus of a hydrogenic atom and have calculated lifetimes and branching ratios for various transitions among the J=0, 1, and 2 states. The J=2 binding energy (${E}_{2}$=101.59 eV) is the first reported variational result for this state. We find that the excited J=0 state is populated several hundred times as often as the ground state.

Measurement of the 2S 1/2–2P 3/2 level splitting in muonic helium: A test of quantum electrodynamics predictions on electronic vacuum polarization

The results of a measurement of the 2S1/2-2P3/2 energy difference in the (μ4He) muonic system are presented. Full account of the experimental method as well as an up-to-date review of the pertaining theoretical predictions are given. The obtained results show a good agreement with QED predictions; the electronic vacuum polarization term of order α is checked with a relative accuracy of 5·10−3.

Atomic and molecular processes involving hydrogen and deuterium muonic systems in matter Formation and elastic scattering of µp and µd muonic atoms

Atomic and molecular processes involving hydrogen and deuterium muonic systems in matter Formation and elastic scattering of µp and µd muonic atoms

Experimental study on the (μ 4He) 2S + metastable system in helium gas

We report the results of an experimental investigation on the properties of the (μ 4He) 2S + metastable muonic system, which was performed stopping negative muons in a pure helium target at pressures ranging from 10 to 50 atm, and observing the total yield and the differential time distribution of the X-rays released in delayed coincidence with the arrival of muons. At each pressureP, information was obtained on the following quantities:a) the total disappearance rate λ2S,tot(P) of the (μ 4He) 2S + system,b) the disappearance rates λA(P) and λSt(itP) of the (μ 4He) 2S + system for external Auger effect and Stark-mixing collisions,c) the fractione 2S of muons stopped in helium which form the (μ 4He) 2S + system. The results obtained on λ2S,tot(P) are in agreement with the results of a cascade calculation, which was performed requiring consistency with previous experimental results; the present measurements show that the variation ofe 2S (P) with pressure in the range (7÷50) atm is small. Good agreement was found between the values for the two-quantum decay rate λ2X of the (μ 4He) 2S + system derived from the present data and the theoretical predictions. The results obtained on λ2S,tot(P), instead, are somewhat in conflict with the results of a recent calculation on λ2St(P). The possible reasons of such disagreement are discussed, referring to possible clustering effects of the helium atoms around the (μHe+ ion.

Observation of muonic X-rays in helium gas and measurement of the two-photon decay rate of the 2s metastable state

We have measured the yield of theK andL lines of the muonic helium system stopping negative muons in a gaseous helium target (7 atm, 293 °K). We have also observed the two-photon decay of the ionie metastable 2s state and we found that this system is formed in (3.4 ± 0.7)% of the stopped muons.