Decay of the low-energy nuclear 229mTh isomer via atomic Rydberg states

In the paper, a unique process of the decay of the (229)mTh(3/2(+), 8.28 +/- 0.17 eV) low-energy nuclear isomer via the internal conversion (IC) channel on Rydberg states is considered for the first time. The Rydberg atom Th-229m(+) e(Ry)(-) is a unique object where IC is possible exclusively on the Rydberg electron e(Ry)(-). It is shown that in the (229)mTh(4+) e(Ry)(-) system (a) IC on the electron states with relatively small values of the principal quantum number n and the orbital moment l is practically completely suppressed, (b) IC probability, W-IC, on the psi(ns1/2) (r) states is proportional to vertical bar psi(ns1/2) (0)vertical bar(2) and can be related with the energy of the hyperfine interaction of the Rydberg electron with the nucleus, (c) W-IC decreases rapidly with the increase of n in the range from 10 to 50, and in the range n greater than or similar to 150 W-IC changes as const/n(3) typical for hydrogen-like ions, and (d) at n approximate to 10-30, W-IC as a function of l has a characteristic "knee" between l = 3 and l = 4, i.e., a decrease of three orders of magnitude in W-IC due to the qualitative change in the ratio between the centrifugal and shielding potentials.