Knowledge Bank

The radiofrequency and microwave spectrum of $NH3-CO2$ has been measured using the molecular beam electric resonance technique. The spectrum is characteristic of an asymmetric top in which the $NH3$ subunit exhibits effectively free internal rotation. The spectroscopic constants obtained for the ground internal rotor state are presented below. [FIGURE] The $N-CO2$ framework of the complex has $C2v$ symmetry with an N-C weak bond length of $2.9875(4)\backslash AA$. The average bending angle of the $NH3$ subunit is $22.71(5)\circ$ with a difference in amplitude of $1.0(4)\circ$ between the in plane and out of plane excursions. (B+C)/2 for the first excited state ($|m|=1$) is 3753.008(2) MHz and the quadrupole coupling constant $eQqaa(|m|=1)-3.176(9)MHz$ is identical with that measured for the ground internal rotor state. The rotational spectrum of the similar complex $NH3-N2O$ has also been obtained. The spectrum is complicated by the quadrupolar hyperfine and internal rotation and we are attempting to obtain the structure and three-fold barrier height for this system. While studying various $NH3$ complexes an intense and complicated spectrum was observed for $ArNH3$. The spectral complexity and observed frequencies demonstrate that this complex is not a symmetrical top.