Microwave optical double resonance spectrum of NH2. III. 1H and 14N hyperfine coupling constants and spin rotation constants in X̃ 2B1

Abstract

Over 200 microwave transitions involving 31 rotational levels in the X̃ ²B₁ state%of NH₂ have been observed using microwave optical double resonance. The majorityh of the observed lines are magnet magnetic dipole allowed transitions between the two spin components of a given rotational state, J=N−1/2←N+1/2, N_kakc The observed lines have been analyzed to yield accurate values for the spin rotation (including those describing the effects of centrifugal distortion), ¹⁴N hyperfine and ¹H hyperfine constants. The three spin rotation constants are determnied to be A_s=−9267.8 (1.4), B_s=−1353.9 (0.5), and C_s=12.0(0.3), where all constants are in MHz and the quoted error in parentheses is three standard deviations. The five centrifugal distortion constants for the spin rotation interaction derived are (in a notation analogous to Watson’s rotational centrifugal distortion constants) Δ^s_N=−0.312(0.007), ΔS_k=−33.9 (0.6), Δ^S_NK=3.51(0.11), δ^s_N=−0.155 (0.004), and δ^s_K=−0.480 (0.077). The ¹⁴N hyperfine constants determined in this analysis are (O)_I=28.2 (0.4), (aa)_I=−42.8 (1.3), (bb)_I=−44.7(1.0), and (cc)_I=87.5 (0.5). The ¹H hyperfine constants are (O)_I=−67.2(0.4), (aa)_I=18.6(1.3), (bb)_I =−13.4(0.9), and (cc)_I=−5.2(0.6). Quadrupole constants for ¹⁴N are also determinable from the data as (aa)_Q=0.1 (1.3), (bb)_Q =−1.6(1.1), and (cc)_Q=1.5(0.6).