In this experiment, the Hf NP was initially held at ~1500 K to establish a baseline rate of mass change (i.e. slope of M vs. time) of -46.1 Da/sec, corresponding to mass loss of 8.85 x 10 -3 Da/sec/nm 2 , assuming spherical shape. As T NP was gradually ramped, the mass loss rate increased, eventually resulting in loss of ~95% of the initial mass by the end of the experiment. The rate became quite rapid above 2200 K, and as T NP exceeded 2400 K, F z tracking was lost, i.e., F z jumped outside the F drive scan range used by our automatic F z tracking algorithm. This can happen when M and/or Q change rapidly, for example, due to fast sublimation, multiple Q steps within a single F drive scan, or if the NP fragments.