Two well-developed Rydberg series of atomic iodine, built on the ...5s(2)5p(4) P-3(1) ion core and assigned to nd[2](5/2) and ns[1](3/2) states with principal quantum numbers as high as n=47, have been observed by two photon (566less than or equal tolambdaless than or similar to600 nm) ionization of I(6s P-2(3/2)), and time-of-flight photoelectron spectroscopy and mass spectrometry. The data reported here extend the nd[2](5/2) and ns[1](3/2) series by 27 and 23 terms, respectively. The limit for both series, 91 387.9+/-1.3 cm(-1), revises upwards by 5.8 cm-1 the value for the I+(P-3(1)) state energy suggested by Minnhagen in 1962 [Ark. Fys. 21, 415 (1962)]. The quantum defects for the nd[2](5/2) and ns[1](3/2) series were determined to be 2.44+/-0.03 and 4.03+/-0.02, respectively. Several terms of a third, weaker series were also detected and tentatively assigned to nd[2](3/2) states, also having the P-3(1) ion core. Photoelectron peaks associated with direct, five photon ionization of I-2 have been observed and are attributed to electronic autoionization of A (2)Pi((3/2)u) ion core Rydberg states into the X (2)Pi((1/2)g,(3/2)g) ionization continua. (C) 2003 American Institute of Physics.