  The nuclear transition between the ground and the low-energy isomeric state
in the ^{229}Th nucleus is of interest due to its high sensitivity to a
hypothetical temporal variation of the fundamental constants and a possibility
to build a very precise nuclear clock, but precise knowledge of the nuclear
clock transition frequency is required. In this work we estimate the
probability of an electronic bridge process in ^{229}Th^35+, allowing to
determine the nuclear transition frequency and reduce its uncertainty. Using
configuration interaction methods we calculated energies of the low-lying
states of Th^35+ and determined their uncertainties.
