We performed the first double junction geometry measurements of quasiparticle
lifetimes and energy distributions.
"Experimental determination of the quasiparticle energy distribution in a non-equilibrium superconductor",
S.B. Kaplan, J.R. Kirtley, and D.N. Langenberg,
Phys. Rev. Lett. **39**,291(1977).

"Quasiparticle Energy Distribution and
Relaxation Times in a Tunnel-Injected Superconductor",
J. R. Kirtley, D. S. Kent, D. N. Langenberg, S. B. Kaplan,
J. J. Chang, and C. C. Yang,
Phys. Rev. B **22**, 1218 (1980).