Mass-selected S-1<---->S-0 two color resonant two photon ionization (2C-R2PI) spectra, fluorescence spectra and fluorescence decay times are measured for supersonically cooled 7-hydroxyquinoline (7HQ).(NH3)(n) clusters with n=4-10. For n=4, the S-1<--S-0 2C-R2PI spectrum shows a 20 cm(-1) broad electronic origin at 27 746 cm(-1), followed by an intermolecular vibrational progression with band widths that increase up to approximate to45 cm(-1). In contrast, the 2C-R2PI spectra of the mixed 7HQ.(NH3)(3)H2O and 7HQ.(NH3)(2)(H2O)(2) clusters exhibit narrow bands of 1-2 cm(-1) width. The large band widths of 7HQ.(NH3)(4) are due to a fast (k>10(12) s(-1)) excited state process which is blocked when replacing one or more NH3 molecules by H2O in the cluster. For the n=5-10 clusters, the 2C-R2PI spectra display two broad absorption bands peaking at 25 000 and 27 000 cm(-1). The latter is characteristic of the 7-quinolinate (7Q(-)) anion, implying that ground state proton transfer from 7HQ to the ammonia cluster occurs for ngreater than or equal to5. Excitation at 27 000 cm(-1) leads to fluorescence from the 7Q(-*) anion clusters at 22 500 cm(-1) with tau(fl)=14-27 ns, and also to fluorescence emission from 7KQ(*) clusters at 18 370 cm(-1) with tau(fl)approximate to7 ns, signaling excited state anion-->keto proton transfer. The 25 000 cm(-1) absorption band is characteristic of ground state 7KQ, implying that the ngreater than or equal to5 clusters also undergo ground state enol-->keto tautomerization. (C) 2003 American Institute of Physics.