Superhyperfine structures of the relaxed excited state of the F centers in KCl observed by zero-frequency optical detection of electron-nuclear double resonance.

Abstract

The superhyperfine (shf) spectrum of the relaxed excited state (RES) of the F centers in KCl has been observed by detecting decrement dips of the quantum efficiency ${\mathrm{\ensuremath{\eta}}}_{\mathit{F}}$ of the F luminescence in its dependence on the magnetic field B below 0.31 T at 4 K. This method is called zero-frequency optical detection of electron-nuclear double resonance (ZF-ODENDOR) described earlier by the Jaccard group. The shf spectrum depends on the angle \ensuremath{\Phi} between B and the crystalline axis. From curve-fitting analysis of its \ensuremath{\Phi} dependence, the isotropic and anisotropic shf interaction constants (a and b) of the RES are determined up to the 32nd shell as a function of \ensuremath{\rho} being the shell distance from an anion vacancy divided by a lattice constant. From the \ensuremath{\rho} dependence of the a values, the envelope wave function (EWF) of the RES is estimated as a \ensuremath{\Vert}2s〉-like EWF admixed with a small fraction (13%) of \ensuremath{\Vert}2p〉-like EWF (Bogan and Fitchen's model). The amplification factors ${\mathit{A}}_{+}$=819 and ${\mathit{A}}_{\mathrm{\ensuremath{-}}}$=950, and an orbital extension constant \ensuremath{\eta}=0.65 for the EWF are adopted. Thus, the advantage of the vibronic model of the RES, that is theoretical extension of Bogan and Fitchen's model, is supported. The ${\mathrm{\ensuremath{\rho}}}^{\mathrm{\ensuremath{-}}3}$ dependence of the ${\mathit{b}}_{1}$ values is confirmed in the range \ensuremath{\rho}\ensuremath{\gtrsim}3.5. \textcopyright{} 1996 The American Physical Society.