This assumption was contradicted initially by Rondeau et al., who found using an ESI source interfaced with a sector mass spectrometer that distributions were narrower than the thermal distribution . Of note, the average energies reported in that study were rather high, so the dissociation may be much faster than the energy exchange, and the internal energy distribution may be truncated at high energies. A later study by the same group considered the desolvation chamber of the ESI source as a collision area and used a partially elastic multiple collision model to account for the accumulation of internal energy in the ions. Here, the internal energy distribution of ions could be compared to a thermal distribution for characteristic temperatures in the range 1020-1550 K ).