Time-domain measurement of spontaneous vibrational decay of magnetically trapped NH

The v=1 -> 0 radiative lifetime of NH(X-3 Sigma(-),v=1,N=0) is determined to be tau(rad,exp.)=37.0 +/- 0.5(stat)-0.8(syst)(+2.0) ms, corresponding to a transition dipole moment of vertical bar mu(10)vertical bar=0.0540(-0.0018)(+0.0009) D. To achieve sufficiently long observation times, NH(X-3 Sigma(-),v=1) radicals are magnetically trapped using helium buffer-gas loading. The rate constant for background helium-induced collisional quenching was determined to be k(v=1)< 3.9x10(-15) cm(3) s(-1), which yields the quoted systematic uncertainty on tau(rad,exp.). With a new ab initio dipole moment function and a Rydberg-Klein-Rees potential, we calculate a lifetime of 36.99 ms, in agreement with our experimental value.