Efficient transfer of population between rotational levels in deuterated ammonia using THz transitions

We demonstrate the efficient transfer of population between rotational levels of ND3 using a com- mercially available table-top THz source. We use a Stark decelerator to prepare a packet of para-ND3 molecules in the 1(,)(-) upper inversion component of the rotational ground state, and induce the 2(1)(+)<- 1(1)(-) electric dipole allowed transition both in the presence of an electric field and under field free conditions. Using THz chirps to address all hyperfine components, transfer efficiencies up to 87% are reached, limited by the power of the THz source. Population transfer from the 1(1)(-), to the 2(1)(-), level is demonstrated either by driving directly the 2(1)(-)<- 1(1)(-), transition in a field, or by a 1(1)(-) -> 1(1)(+)-> 2 (-)(1)double-resonance excitation scheme. In addition, we present a novel method to produce packets of ND3 (1(1)(-)) with pure M-J = 0 or vertical bar M-J vertical bar = 1 character using the Stark decelerator, and a method to probe the M-J composition of a packet of molecules using THz excitation. [GRAPHICS] .