Negative Ion of Boron: An Experimental Study of the 3P Ground State

An investigation of the B-(2p2 3PJ)→B(2p 2PJ′) photodetachment thresholds using a tunable infrared laser source has yielded a substantially improved value for the electron affinity of boron and the first 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 and 5.18(15) cm-1, respectively, and the electron affinity is determined to be 2256.12(20) cm-1 [(279.723(25) meV]. The present result for the electron affinity is the first to challenge the extensive and controversial theoretical studies of this system.