Photodetachment of Na-

Eigenchannel R-matrix calculation results are presented for the photodetach ment partial cross sections of Na- for energies up to the Na(Sp) threshold. The photoelectron angular distribution asymmetry parameter for the process Na- + gamma-->Na(3p) + e(-) is also presented over the same energy range. Detailed analyses and identifications of P-1(o) resonance structures are pr esented and compared with corresponding ones in H- and Li-. Our results are compared with works of others, including the four-state close-coupling res ults of Moores and Norcross [Phys Rev. A 10, 1636 (1974)], the resonances o bserved by Johnston and Burrow [Phys. Rev. A 51, 406 (1995)] in studies of temporary negative ion formation in electron scattering by Na atoms, and th e recent relative Na(4s) partial cross-section measurements of G. Haeffler et al. [following paper, Phys. Rev. A 59, 3655 (1999)]. [S1050-2947(99)1150 5-1].