The resonant two-photon ionization (R2PI) and mass analyzed threshold ionization (MATI) spectra of N-deuterium. substituted indoline (indoline-d1) have been recorded. The origin of the S-1 <-- S-0 transition and the adiabatic ionization energy (IE) are found to be 32254 +/- 1 and 58284 +/- 5 cm(-1), corresponding to the isotope shifts of 38 and 15 cm(-1), respectively. Comparing these data with those of N-deuterated aniline suggests that the five-membered ring is responsible for the observed blue shifts in the electronic energy and IE of indoline-dl. The present results also show that the N-deuteration can lead to a reduction in the frequencies of the characteristic C-2-puckering, butterfly, ring twisting, and N-inversion vibrations of indoline. (C) 2003 Elsevier Science B.V. All rights reserved.