Pure Rotational Spectroscopy of the CH 2 CN Radical Extended to the Sub-Millimeter Wave Spectral Region.

We present a thorough pure rotational investigation of the CH ₂ CN radical in its ground vibrational state. Our measurements cover the millimeter and sub-millimeter wave spectral regions (79-860 GHz) using a W-band chirped-pulse instrument and a frequency multiplication chain-based spectrometer. The radical was produced in a flow cell at room temperature by H abstraction from acetonitrile using atomic fluorine. The newly recorded transitions of CH ₂ CN (involving N ″ and K _a ″ up to 42 and 8, respectively) were combined with the literature data, leading to a refinement of the spectroscopic parameters of the species using a Watson S-reduced Hamiltonian. In particular, the A rotational constant and K -dependent parameters are significantly better determined than in previous studies. The present model, which reproduces all experimental transitions to their experimental accuracy, allows for confident searches for the radical in cold to warm environments of the interstellar medium.