Terahertz Spectroscopy of the Amidogen Radical, NH2.

The rotational spectrum of the NH2 radical in its &Xtilde;2B1 ground vibronic state was investigated between 614 and 1003 GHz. One hundred fifty-nine newly observed lines (188 hyperfine components) of six rotational transitions with 0 </= N </= 5 and 0 </= Ka </= 4 were used in the final, global fit of field-free data for the (000) vibrational state. Recent results from Fourier transform far-infrared (FT-FIR), and millimeter- and submillimeter-wave spectroscopy, as well as microwave optical double resonance (MODR) and recent FIR laser sideband data, were also used in the fit. A large set of spectroscopic constants reproduces the input data within experimental uncertainties and permits the precise prediction of low-N, low-Ka transitions of interest for the astrophysical community. In particular, the astrophysically important 111-000 transition of ortho NH2 was observed near 952.57 and 959.50 GHz. Copyright 1999 Academic Press.