NEGATIVE-ION OF BORON - AN EXPERIMENTAL-STUDY OF THE P-3 GROUND-STATE

An investigation of the B-(2p(2 3)P(J)) --> B(2p P-2(J),) photodetachm ent thresholds using a tunable infrared laser source has yielded a sub stantially improved value for the electron affinity of boron and the f irst experimental data on the fine structure of the ionic ground state . The J = 0-1 and J = 1-2 splittings are found to be 3.23(15) cm(-1) a nd 5.18(15) cm(-1), respectively, and the electron affinity is determi ned to be 2256.12(20) cm(-1) [(279.723(25) meV]. The present result fo r the electron affinity is the first to challenge the extensive and co ntroversial theoretical studies of this system.