Rates of transitions between the hyperfine-splitting components of the ground-state and the 3.5 eV isomer in 229Th89+

For the hydrogenlike Th-229(89+) ion, the rates of electromagnetic M1 transitions between hyperfine structure levels, originating from the nuclear 5/2(+) ground state and the first excited 3.5+/-1.0 eV 3/2(+) isomeric state, are calculated. As a result of the mixing of the F = 2 components, these transitions turn out to be faster than the nuclear isomeric gamma transition in a bare nucleus by several orders of magnitude. The possibility of experimental observation of these transitions is discussed.