Experimental cryo-SEVI spectra of FNH3¯ are shown in Fig. and show the photoelectron intensity as a function of electron binding energy (eBE). The overview spectrum in blue shows a smoothly rising background from 26050 to 29050 cm -1 , after which there is/ a series of steps out to 32000 cm -1 (k-p). Above this, one observes a series of partially resolved peaks (q-t). Considerably more structure is observed in the higher resolution composite spectra (black). Starting at 26050 cm -1 , there is an extended progression of peaks a-m that progressively become more tightly spaced as eBE increases. Spacings between peaks a-b and k-l, for example, are 293 and 187 cm -1 , respectively. At higher eBE, a series of broad features n-p spaced by ∼700 cm -1 is seen, followed by a third progression, peaks q-t, spaced by ∼300 cm -1 . A full listing of peak positions and spacings can be found in the SI (Table ). The locations of the reactant asymptote (black arrow) and the TS (gray arrow) are also indicated in the figure, at 33022 and 28981 cm -1 , respectively.