Excited-state lifetimes for a number of vibronic states of (1)Pi(u) symmetry in molecular nitrogen have been determined experimentally in a laser-based pump-probe scheme using a coherent and tunable extreme ultraviolet source based on harmonic generation. States investigated in N-14(2) were b(1)Pi(u)(v = 6-9), of valence character, and c(3)(1)Pi(u)(v = 1) and o(3)(1)Pi(u)(v = 1), of Rydberg character. In the case of b(1)Pi(u)(v = 7) and c(3)(1)Pi(u)(v = 1), rotationally dependent predissociation was observed. States studied in N-15(2) were b(1)Pi(u)(v = 5) and c(3)(1)Pi(u)(v = 1); in addition, lifetimes of the c(4)'Sigma(u)(+)(v = 0,1) and b'(1)Sigma(u)(+)(v = 1) states were determined. The lifetimes show a dependence on the vibrational quantum number and isotope. (C) 2004 Elsevier B.V. All rights reserved.