Electrostatic trapping of metastable NH molecules

We report on the Stark deceleration and electrostatic trapping of ¹⁴NH (a¹Δ) radicals. In the trap, the molecules are excited on the spin-forbidden A³∏ <- a¹Δ transition and detected via their subsequent fluorescence to the X³∑⁻ ground state. The 1/e trapping time is 1.4 ± 0.1 s, from which a lower limit of 2.7 s for the radiative lifetime of the a¹Δ, v=0, ,J=2 state is deduced. The spectral profile of the molecules in the trapping field is measured to probe their spatial distribution. Electrostatic trapping of metastable NH followed by optical pumping of the trapped molecules to the electronic ground state is an important step towards accumulation of these radicals in a magnetic trap