  We have studied the effect of atomic electrons on the nuclear transition from
the isomeric {229m}Th state to the ground {229g}Th state in {229}Th+ due to the
electronic bridge process. The exact value of the nuclear transition frequency
is unknown so far; therefore, we have developed a formalism that can be used
for any nuclear transition frequency. We have calculated positions of several
high-lying even-parity states which are not presented in experimental atomic
spectra databases. We have found their energy levels and g factors.
