The rotational spectrum, barrier to internal rotation, and structure of NH3–N2O

Abstract

The rotational spectrum of NH3–N2O has been observed by the molecular beam electric resonance method. The spectrum is characteristic of a T-shaped complex in which the nitrogen of the NH3 subunit is directed toward the N2O subunit. The NH3 unit exhibits nearly free internal rotation about its C3 axis. The A internal rotor state transitions were fit to Watson’s asymmetrical top Hamiltonian and the following spectroscopic constants were determined: A(MHz)=12 722.5(5), δK (MHz)=0.22(2), B(MHz)=4 083.5(2), δJ(MHz) =0.007(1), C(MHz)=3 070.8(2), ΔK(MHz) =−0.3(2), ΔJ(MHz) =0.016(9), ΔJK(MHz) =0.32(3), μa(D) =1.514(9), μb(D) =0.09(9). The E internal rotor state transitions were fit to the Hamiltonian of Kilb, Lin, and Wilson. For the E internal rotor state the rotational constants A [12 743(64) MHz], B[4077.1(12) MHz], and C[3069.9(9) MHz] were determined, as well as the height of the barrier to internal rotation, V3 [12.5(25) cm−1]. The distance between the nitrogen of the NH3 to the center of mass of N2O is 3.088 Å. The angle between the C3 axis of NH3 and the line joining the centers of mass of the NH3 and N2O subunits is 13°. The C3 axis of NH3 is pointed towards the nitrogen end of the N2O subunit.