Gas phase reaction of B2H6 With HN3 at 400 degrees C yields tetraazidodiborane (TADB), which subsequently dissociates into two diazidoborane molecules. Exposure of TADB to vibrationally excited SF6 generates free BH radicals that may be pumped by energy transfer from metastable NF(a(1) Delta) molecules, obtained by simultaneous dissociation of FN3. Even though BH radicals are rapidly consumed, the transient yields approach 2% of initial donor concentration. The rate constants for sequential excitation of the a(3) Pi and A(1) Pi states of BH by NF(a(1) Delta) are estimated to be similar to 8 x 10(-10) and similar to 3 X 10(-11) cm(3)/s, respectively, and transient population inversions with peak optical gains of 10%/cm are developed on the BH(A - X) transition at 433 nm.