| Description |
We propose to perform a deep search for the CH2D+ ion with Herschel-HIFI. This species plays a key role in interstellar chemistry, especially for deuterium fractionation at moderate temperature, but also as tracer of the symmetrical species CH3+. Because of its low dipole moment, and floppy character, its rotational transitions were not accurately known until recently (Amano 2010). Also, only two millimeter transition and one submillimeter transition are available from the ground, but in spectral regions where multiple emission lines from other species are present. Therefore, this ion escaped detection despite extensive searches by some of the proponents for over 30 years. Three of the most intense lines of CH2D+ are accessible to Herschel-HIFI in relatively clean spectral regions. The detection of CH2D+ seems therefore to be finally within reach, providing a key proof of the validity of state of the art chemical networks. |
