The First Detection of CH₂CN in a Protoplanetary Disk

We report the first detection of molecule cyanomethyl, CH$_2$CN, in a protoplanetary disk. Until now, CH$_2$CN had only been observed at earlier evolutionary stages, giant molecular clouds TMC-1 and Sgr 2, prestellar core L1544. detect six transitions ortho-CH$_2$CN towards disk around nearby T Tauri star TW Hya. An excitation analysis reveals that disk-averaged column density, $N$, for is $(6.3\pm 0.5)\times10^{12}$ cm$^{-2}$, which rescaled to reflect 3:1 ortho-para ratio, resulting total $N_{\rm tot}$, $(8.4\pm 0.7)\times10^{12}$ cm$^{-2}$. calculate disk-average rotational temperature, $T_{\rm{rot}}$ = $40 \pm 5$ K, while radially resolved shows remains relatively constant across radius This high rotation temperature suggests static if vertical mixing can be neglected,CH$_2$CN largely formed through gas-phase reactions upper layers disk, rather than solid-state on surface grains midplane. The integrated intensity radial profiles show ring structure consistent with molecules such as CN DCN. note this also previous lower-resolution observations centrally peaked CH$_3$CN emission Hya disks, since gap disappears when convolving our larger beam size. obtain CH$_2$CN/CH$_3$CN ratio ranging between 4 10. reproduced representative chemical model employs standard chemistry assumptions, i.e. without any additional tuning.