Laser excitation of isotopically labeled SO2 molecules in a neon matrix has allowed the measurement of dispersed phosphorescence spectra (ã3B1-X̃1A1) in the wavelength region 387.5-526.3 nm (19 000-25 800 cm-1). The origin of the ã-X̃ transition lies at 25 747 cm-1 in 16OS16O, shifted 18 cm-1 to the red from the gas phase; the three vibrational frequencies of the X state are nearly unperturbed in the neon matrix (1149, 520, and 1362 cm-1). As the zero-phonon lines are sharp and well resolved, it has been possible to monitor emission from a specific isotopomer to obtain its excitation spectrum. The excitation spectra of matrixisolated 16OS16O and 18OS18O in the region 350.9-388.5 nm (25 740-28 500 cm-1) are similar to those previously observed in the gas phase, with strong perturbations affecting all vibrational levels above ãB1(110) at 27 005 cm-1 (370 nm). Two additional groups of bands are observed for the unsymmetrical isotopomer 18OS16O; they are identified as transitions to levels of the ã3B1 state with v3 = 1 and as direct transitions to the b̃3A2 state, which both become allowed in the lower symmetry. The v3 frequency of the ã3B1 state of 18OS16O is 922 cm-1; for the b̃3A2 state, v1 - 791 cm-1 and v2 ≃ 315 cm-1, while the b̃ (001) level z lies 26 653 cm-1 above the X̃ (000) level.