Design, performance, and applications of a pulsed, single mode optical parametric oscillator (OPO) for studies of high resolution spectroscopy and photodissociation dynamics are presented, Single mode operation is achieved by resonantly seeding a four-minor OPO ring cavity With a tunable, continuous wave (cw) ring dye laser, providing continuous scanning capability at near Fourier transform limited resolution [Delta nu=160(20) MHz] with peak output energies greater than or equal to 10 mJ. The high spectral brightness of this OPO light source is sufficient to saturate Delta nu =3 stretching transitions in OH, NH, and CH vibrational manifolds, which makes feasible quantum state-selected multiple resonance spectroscopies at 0.005 cm(-1) resolution, The capability of this single mode OPO is explicitly demonstrated via ii) nu(OH)=3<--0 overtone spectroscopy of HOD, (ii) near-IX optical saturation studies of H2O in the /03(-)) overtone vibrational manifold, (iii) high resolution LIF Dopplerimetry of OH radicals, and (iv) IR/UV multiple resonance spectroscopy of Ar-H2O molecular clusters. (C) 1997 American Institute of Physics.