4 pages, 2 tables, 3 figures.-- PACS nrs.: 25.60.Gc, 21.10.Pc, 25.60.Dz, 27.30.+t.Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope O-23. The O-22 fragments produced in one-nucleon removal from O-23 at 938 MeV/nucleon in a carbon target were detected in coincidence with deexciting γ rays. The widths of the longitudinal momentum distributions of the O-22 fragments and the one-neutron removal cross sections were interpreted in the framework of a simple theoretical model which favors the assignment of Iπ=1/2+ to the O-23 ground state.This work was supported by EU (ERBFMGECT95 0083), Internationales Büro Osteuropa-Verbindungsbüro des BMBF bei den DLR (WTZ Bonn SLA-002-96-BMBF and 06DA915I), NFR Sweden (F5102-1484/2001), and MCyT, Spain (FPA-2001-C05-4-01).Peer reviewed