Knowledge Bank

Using the technique of microwave optical double resonance (MODR) with dye laser excited fluorescence detection, several excited state transitions to the previously uncharacterized $220$ vibronic level of $NH2$ have been measured and both the proton and nitrogen hyperfine splittings have been resolved. These electric dipole-allowed transitions (tentatively assigned as) $X~2B1(0,12,0),220\leftarrow A~2A1\Pi (0,10,0),110,J=3/2\leftarrow 1/2$ are in the region of 6.3 GHz. Together with an earlier determination of the hyperfine structure in the $110,J=3/2$ and J = 1/2 levels, these results have allowed us to assign the hyperfine splitting pattern of the $220$ level. This provides new information, both on the hyperfine constants of a highly excited vibrational state of $NH2$, and on the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}A1$ level of this radical.