American Physical Society, Physical Review Letters, 8(100)
DOI: 10.1103/physrevlett.100.083003
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The v = 1 -> 0 radiative lifetime of NH (X triplet-Sigma-, v=1,N=0) is determined to be tau_rad,exp. = 37.0 +/- 0.5 stat +2.0 / -0.8 sys miliseconds, corresponding to a transition dipole moment of |mu_10| = 0.0540 + 0.0009 / -0.0018 Debye. To achieve the long observation times necessary for direct time-domain measurement, vibrationally excited NH (X triplet-Sigma-, v=1,N=0) radicals are magnetically trapped using helium buffer-gas loading. Simultaneous trapping and lifetime measurement of both the NH(v=1, N=0) and NH(v=0,N=0) populations allows for accurate extraction of tau_rad,exp. Background helium atoms are present during our measurement of tau_rad,exp., and the rate constant for helium atom induced collisional quenching of NH(v=1,N=0) was determined to be k_q