Quadrupole corrections to matrix elements of transitions in resonant reactions of muonic molecule formation

The calculated resonant formation rates of the muonic molecules ddµ and dtµ are presented. The approach developed earlier for calculating the transition matrix elements in the dipole approximation has been extended to include the quadrupole terms in the multipole expansion of the interaction operator. The calculated dependence of the dtµ formation rates on the energies of the incident tµ muonic atoms shows that the effect of including the quadrupole correction is to reduce the magnitude of the peak rates by about 20–30% at the different temperatures, compared to those calculated in the dipole approximation. The dependence on temperature for the ddµ formation rates is obtained with the differences between the presented and previous calculations being less than 5%.     

Encapsulation of organotin compounds in metal acetate glasses

Triorganotin halides, oxides and sulphides can be dissolved in molten, mixed-metal acetates at ca 140–160°C without decomposition; quenching provides glasses into which are encapsulated the organotin species. Halide/acetate and oxide/acetate, but not sulphide/acetate, exchanges occur in the melt. Only partial exchange was found for hindered trineophyl tin chloride [(PhCMe₂CH₂)₃SnCl], in contrast to the complete exchanges observed for the butyl (Bu), phenyl (Ph) and cyclohexyl (Cy) analogues. Complete oxide/acetate exchange was found for (Bu₃Sn)₂O, partial exchange occurred for (Cy₃Sn)₂O, whilst no exchange resulted with bis(trineophyltin) oxide or (Ph₃Sn)₂O. Tin–tin bonds (e.g. as in Ph₃SnSnPh₃) and carbon–tin bonds (even the allyl–Sn bond in Bu₃SnCH₂CH?CH₂) are not affected. The acetate glasses dissolve in aqueous media with release of the organotin species and they have potential as slow-release systems which is currently being investigated.     

Disproportionation of triorganotin species,R3SnX

Triorganotin compounds, R₃SnX, have found extensive use as a biological agents in such areas as agrochemicals, marine antifoulants and timber preservatives. In contrast, di(R₂SnX₂) and tetraorganotin derivatives (R₄Sn) possess less biological activity than do their triorganotin counterparts. It has been shown that disproportionation of R₃SnX species (i.e. to produce R₂SnX₂ and R₄Sn) can occur especially when X is a chelating or bridging group such as oxide, carboxylate, hydroxy ketone or hydroxyquinoline. This process has implications for the industrial applications and analysis of R₃SnX compounds.     

Analysis of probabilities for nuclear excitation by near-resonant electronic transitions

Theoretical results are presented for nuclear excitation of low-lying isometric states of ¹⁹⁷Au, ¹⁸⁹Os and ²³⁷Np by a near-resonant electronic deexcitation process known as NEET. A detailed comparison is made between current and previous theoretical results in order to clarify a number of anomalies. For ¹⁹⁷Au, the only case in which the current experimental precision appears to be sufficient to provide a stringent test of theory, the theoretical result for the NEET probability is P_NEET=3.6×10⁻⁸. This is a factor of three lower than previous theoretical results and reduces the difference between theory and the recent experimental result, P_NEET=(5.0±0.6)×10⁻⁸, to a level of approximately 2σ.     

Asymptotic form of three-body (dtµ)+ and (ddµ)+ wave functions

In order to investigate a discrepancy between existing literature values for the normalization constant in the asymptotic form of three-body wave functions for (dtµ)⁺, we report the results of a new calculation of the normalization constants for this system as well as the related system (ddµ)⁺. These were obtained by fitting to accurate variational wave functions with special care being taken to describe the long-range behavior.     

First results with DIAMANT and EUROGAM

The coupling of efficient particle and γ detection arrays is a powerful tool to study the deexcitation of both compound and residual nuclei in fusion evaporation reactions.We show first results obtained coupling the DIAMANT (4π light charged particle array) and EUROGAM (4π γ array) detectors demonstrating the improvement in the resolving power by this combination. For γ rays of ?800keV improvements in the Doppler correction up to 50% have been reached for the 2α exit channel following the fusion of 32S+58Ni at 120 MeV bombarding energy (β ? 3%).     

Energy shift in (dtμ)e due to the finite size of the muonic molecular ion (dtμ)+

The energy shift due to the presence of the extended (dtμ)₁₁ pseudonucleus (in its first excited state with one unit of angular momentum) in the quasihydrogenlike system (dtμ)₁₁ e _1s is estimated using perturbation theory up to second order with two choices of zeroth order electron wavefunctions. The energy shift is found to be 0.50 meV using pure Coulomb electron wavefunctions and 0.58 meV using electron wavefunctions calculated with a potential modified to take partial account of the finite size of (dtμ)₁₁. In both cases, the perturbation Hamiltonian is expanded in multipoles, retaining terms up to and including octupole terms.     

A rare nuclear decay process: The internal conversion between bound atomic states

We shall report on the recently observed dependence of the lifetime of the first excited state in ¹²⁵Te on the ionic charge state. Then we shall give an interpretation of the dependence of the half-life in terms of a new type of nuclear internal conversion without emission of the electron into the continuum of electron energies. We have named this process internal conversion between bound atomic states or BIC. The resonant character of the BIC will be established and the main parameters governing the decay process will be discussed [1–3]. Finally the results of a recent experiment performed at the GANIL accelerator attempting to measure directly the value of the internal conversion coefficient associated with BIC in ¹²⁵Te ions with charge states ranging between 44+ and 48+ will be given. In conclusion we shall discuss the relation between the BIC and nuclear excitation by electron transition, NEET, in the excitation of some nuclear isomeric states.