Detection of OH 18-cm Emission from Comet C/2020 F3 NEOWISE using the Arecibo Telescope

We report the detection of emission from the OH 18 cm $\mathrm{\Lambda }$-doublet transitions toward Comet C/2020 F3 NEOWISE using the Arecibo Telescope. The antenna temperatures are 113$\pm$3 mK for the 1667 MHz line and 57$\pm$3 mK for the 1665 MHz line. The beam averaged OH column density (centered on the comet nucleus) derived from the 1667 transition is $N_{OH}$=1.11$\pm 0.06\times {10}^{13}$ cm${}^{-2}$. We implemented the Haser model to derive an OH production rate. The estimated OH production rate using the 1667 MHz transition is Q${}_{OH}$=3.6$\pm 0.6\times {10}^{28}$ s${}^{-1}$, a factor of 2.4 lower than optically derived values for the same observing day, the difference of which is likely explained by quenching.