The dispersed fluorescence (DF) spectra of the 7-azaindole dimer (7AI(2)) and deuterated dimers 7AI(2)-hd and 7AI(2)-dd, where hd and dd indicate the deuteration of an imino proton and two imino protons, have been measured in a supersonic free jet expansion. The undeuterated 7AI(2)-hh dimer exhibits only the tautomer fluorescence, but both the normal and tautomer fluorescence have been detected by exciting the origins of 7AI(2)-h*d, 7AI(2)-hd* and 7AI(2)-dd in the S-1-S-0 region, where h* and d* indicate the localization of the excitation on 7AI-h or 7AI-d moiety. The DF spectra indicate that 7AI2-h*d and 7AI2-hd* undergo excited-state proton/ deuteron transfer (ESPDT), while excited-state double-deuteron transfer (ESDDT) occurs in 7AI2-dd. The H/D kinetic isotopic effects on ESDPT have been investigated by measuring the intensity ratios of the normal fluorescence to the tautomer fluorescence. The ESPDT rate is about 1/60th of the ESDPT rate, and the ESDDT rate is about 1/12th of the ESPDT rate, where ESPDT rate is an average of the rates for 7AI(2)-h*d and 7AI(2)-hd*. The observed H/D kinetic isotope effects imply that the ESDPT reaction of 7AI(2) has a "cooperative" nature; i.e., the motion of the two moving protons strongly couples each other through the electron motions. The difference in the estimated ESPDT reaction rates, 9.8 x 10(9) and 6.9 x 10(9) s(-1) for 7AI(2)-h*d and 7AI(2)-hd*, respectively, is consistent with the concerted mechanism rather than the stepwise mechanism.