The C/CO ratio in B335 and the decaying dark matter neutrino hypothesis

C¹⁸O J = 2−1, C¹⁷O J = 2−1 and [C i] ³P1−³P0 emission from the dense cold cloud B335 has been observed and modelled in order to determine the C/CO ratio. The observed ratio is compared with a prediction by Tarafdar who assumes a mechanism in which the CO dissociation is caused by photons of energy ∼ 13.8 eV. These were postulated by Sciama to result from the decay of dark matter neutrinos. Our value for the C/CO ratio sets an upper limit to the strength of the neutrino decay dissociation process, thus providing a significant datum for interstellar chemistry theory.