The estimated temperature of the plum ranges from 400 K to 2,200 K or higher. Assuming the energy distribution among the ion pairs follows the Boltzmann equation, these temperatures correspond to a fraction of 1.4 × 10 -11 to 1.1 × 10 -2 ion pairs that have the required 1.38 × 10 -19 J thermal energy to be separable into free ions by the ion extraction potential. If the temperature of 1,000 K is assumed, the number is 4.6 × 10 -5 . These numbers are related to the ion yields observed in MALDI MS experiments according to the ion pair thermal model.