Brightness profiles of C3 and NH3 in the atmosphere of P/Brorsen-Metcalf

Spectroscopic observations of Comet P/Brorsen-Metcalf were made on August 9–13, 1989. Spatial profiles extracted from long-slit spectra were analyzed to determine the lifetimes of C₃ and NH₂ radicals and their parents, as well as the tailward acceleration of these radicals. In our investigations we used a Monte Carlo model. The average lifetime for C₃ has been found to be 6.3 × 10⁴ s and that for the parent of C₃ to 6 × 10³ s. The spatial profiles of C₃ were almost symmetric and we need only 0.1 cm s^?2 as the tailward acceleration. According to our simulations, C₃H₄ (allene) can be considered as the parent for C₃. We obtained the average value 7.6 × 10⁴ s for the lifetime of NH₂ and 1.1 × 10⁴ s for the lifetime of the NH₂ parent. The tailward acceleration of NH₂ was not more than 0.1 cm s^?2. This result does not exceed the latest theoretical calculations of NH₂ and NH₃ lifetimes by a factor of 1.4. So, NH₃ may be considered as a parent for NH₂ in the atmosphere of P/Brorsen-Metcalf.