FIZIKA B 1 (1992) 1, 71-82

RESONANCE EFFECT IN INNER-SHELL nd®1s TWO-PHOTON DECAY

KSENOFONT ILAKOVAC
Department of Physics, Faculty of Science, University of Zagreb P.O.Box 162, 41001 Zagreb, Croatia
and
Ruđer Bošković Institute, 41001 Zagreb, Croatia

Received 15 February 1992

Emission of photon pairs by the two-photon decay process from silver and hafnium atoms with a vacancy in the K shell was investigated. Radioactive decay of ¹⁰⁹Cd and ¹⁷⁹Ta was used to generate the K-shell vacancy states in silver and hafnium atoms, respectively. The measuring system consisted of a pair of planar high-purity germanium detectors, a fast-slow coincidence system, and a 128x512x512 channel pulse-height analyzer. Two-dimensional spectra of numbers of events as functions of amplitudes of coincident pulses from the two detectors were analyzed. The results on the 3d ® 1s two-photon decay show the resonance behaviour, seen as a gradual increase of the differential transition probability as the partition of energy among the two photons of the pair deviates from equal-energy partition (E₁=E₂=E₀/2). The effect was predicted by the second-order perturbation theory of two-photon decay in which summation over intermediate states is carried out over occupied and unoccupied bound states, and over unbound states.

UDC 539.122

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