Fractional gas-phase abundances with respect to total hydrogen of nitrogen-bearing species observed in G+0.693. The first vertical line indicates the approximate time for the peak abundances of the species. The second vertical line indicates the time when the gas temperature has returned to the starting temperature of 100 K. The four panels represent the four setups with increasing CRIR (a) S-LCR, S-MCR, S-HCR, and S-VHCR.