PH_2_CN/CH_3_PH_2_ rotational transition frequency

For PH_2_CN, the spectra were fit with a Watson S-reduced asymmetric top Hamiltonian, resulting in more accurate rotational and centrifugal distortion constants. In the case of CH_3_PH_2_, an asymmetric top internal-rotation Hamiltonian was employed in the analysis, significantly improving the rotational and torsional parameters over previous microwave estimates. Searches for both molecules were subsequently conducted toward Sgr B2(N), using the 12 m telescope of the Arizona Radio Observatory (ARO).

Neither species was identified, with abundance upper limits, relative to H_2_, of f(PH_2_CN/H_2_)<7.0x10^-12^ and f(CH_3_PH_2_/H_2_)<8.4x10^-12^. The nitrogen analogs NH_2_CN and CH_3_NH_2_ are therefore more abundant in Sgr B2(N) by factors of >2 and >200, respectively.