COMPETITION BETWEEN PARTICLE-HOLE AND PARTICLE-PARTICLE CORRELATIONS IN FORBIDDEN ELECTRON-CAPTURE - THE CASE OF TE-123

The K-electron capture half-life of Te-123 has been recently measured to be t(exp)(K)=2.4x10(19) yr and constitutes the longest half-life ev er measured in a single beta-transition of any nuclear species. We hav e calculated this second unique forbidden transition within the framew ork of the proton-neutron quasiparticle random phase approximation, ma king use of Skyrme-type effective interactions. A strong cancellation effect between particle-hole and particle-particle correlations is fou nd. The model, without any renormalization of the force, provides a lo wer limit for the K-electron capture half-life of similar to 10(17) yr , which unambiguously rules out the old experimental values of 10(13)- 10(14) yr. A few percent increase of the particle-particle matrix elem ents of the Skyrme interaction allows one to reproduce the experimenta l findings.