Lifetime measurements in25Mg

We present analytic solutions of the Eilenberger equations for the low-frequency Green's functions corresponding to those quasiparticles whose trajectories pass near the center of an isolated vortex. Using these results we find that for type II superconductors in the temperature rangeT _c ?T?T _c ²/ε_F the order parameter and the supercurrent near the vortex center increase over a lengthξ ₁～ξ _BCS T/T _c (ξ _BCS=BCS coherence length) and that the density of states at the Fermi surface isN ₀ 2π ³ ξ _BCS ² /3 In (ξ _BCS/ξ ₁). The results can be reproduced with the Bogoliubov equations for the elementary excitations. It is shown that this peculiar behavior is connected with the low-lying bound states in the vortex core. ForT? _c ²/ε _F one hasξ ₁～k _F ^?1.