In the gas phase, the tendency for neutralization via ion pair formation in equations (7-9) should be similar as discussed earlier. The tendency for neutralization via proton transfer as shown in equations (8-9) can be estimated by the corresponding equilibrium constants, and they are 557 kJ/mol or 10 29 and 577 kJ/mol or 10 30 , respectively when a pKa of 1296 kJ/mol of dimethyl hydrogen phosphate is used for Nuc-O3POH, pKa of 739 kJ/mol of ammonium is used for R3NH + , pKa of 719 kJ/mol of carboxylic acid is used for [M+H] + , and the plume temperature is assumed to be 1,000 K. At 2,200 K, under otherwise the same conditions, the numbers become 585 kJ/mol or 10 14 for the case of equation ( ) and 593 kJ/mol or 10 14 for the case of equation (9). In all cases, the equilibria strongly favor the neutral species.