Calculated radial profiles of the G/R ratio in different comets. The input parameters used to calculate the G/R ratio are tabulated in Table 1. It can be seen that in comets C/2006 W3 and C/2001 Q4, due to substantial collisional quenching of O(¹S) and O(¹D) with other cometary species, the calculated G/R ratio is more than 1 closer to the nucleus, whereas above 400 km projected distances it is a constant.