Examining the spectral evolution of the data in Figure , the negative features in the spectra associated with water desorption increase from a pump-probe delay of t = 0 to ca. 10 -4 -10 -3 s, followed by recovery as the sample begins to return to its equilibrium conditions. The shifts of the silanol and free Brønsted ZOD modes due to the heating of the sample evolve on a different timescale from the modes associated with water desorption, evidenced by the water desorption modes persisting in the spectra at 10 -2 s while these other features are already fully decayed. The kinetics of the silanol and waterassociated modes in the spectra at different temperatures are shown in ESI Section 6. We now turn to establishing the heating and cooling behaviour of the zeolite on laser excitation.