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Front Cover: Excitation density, diffusion‐drift, and proportionality in scintillators (Phys. Status Solidi B 2/2011)
Author(s) -
Williams R. T.,
Grim Joel Q.,
Li Qi,
Ucer K. B.,
Moses W. W.
Publication year - 2011
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Reports
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201190002
Subject(s) - streak camera , picosecond , atomic physics , scintillator , electron , excitation , quenching (fluorescence) , physics , optics , laser , detector , fluorescence , quantum mechanics
The front cover image points to the Feature Article by Williams et al. ( pp. 426–438 ). A gamma ray interacting with a solid launches a cascade of high energy electrons whose ionization tracks may be considered roughly gaussian cylinders of about 3 nm initial radius, depicted by the red inner cylinder (where the electron moves from left to right). Carriers with different mobilities are separated in the strong radial gradient of excitation density n , more so in the beginning than end of the track due to drift confinement. Nonlinear quenching of excitons by dipole–dipole transfer competes on a picosecond time scale with diffusion to reduce electron–hole density in the track, reducing the luminescent yield in a scintillator by different amounts depending on position along the track. Variation of local light yield along the track results in a fundamental limitation on the energy resolution of a radiation detector called nonproportionality. In this article, luminescence quenching dependence on excitation density is measured by a sub‐ps band‐gap laser pulse, illustrated here by the streak camera display. The measured rate constants for nonlinear quenching are used in a numerical model of competing diffusion and quenching to examine trends underlying nonproportional light yield in CsI:Tl.