Spontaneous emission probability for M1 transition in a dielectric medium: Th-229m(3/2(+), 3.5 +/- 1.0 eV) decay

The probability of spontaneous magnetic dipole emission in a transparent dielectric medium with refractive index n is shown to be n(3) times higher than in vacuum. The decay of a low-lying nuclear Th-229m(3/2(+), 3.5 +/- 1.0 eV) level in the (ThO2)-Th-229 dielectric is discussed. (C) 2000 MAIK Nauka/Interperiodica.