Fig. 3: The transient \({{{{{{\rm{SiH}}}}}^{+}_{4}}}\) species and its decay into \({{{{{{\rm{SiH}}}}}^{+}_{2}}}\).
a Results of the longer ATAS measurement (Fig. 1b) showing the \({{{{{{\rm{SiH}}}}}^{+}_{2}}}\) fragment’s transient absorption. The right-hand panel compares time-averaged transient spectra and their non-linear correction (ΔA)1.21 (greyscale) with synchrotron results17 (coloured). The absorption between 109.7 and 110.7 eV is integrated and plotted as a function of pump-probe delay in (b), in which a negative exponential decay fit reveals a 140 ± 19 fs decay constant. c The spectral signature and vibrational dynamics of the JT-distorted \({{{{{{\rm{SiH}}}}}^{+}_{4}}}\) species (highlighted with dashed rectangles). The transient spectrum is produced by applying a 4-THz-wide Fourier filter to the ATAS results, followed by a 33% depletion correction (see Supplementary Section S3.5). The right-hand panels show the result of a Fourier transform over the first 100 fs and 300 fs, respectively, and highlight the strongest Fourier frequencies with dashed vertical lines. The 42 THz signals are caused by ν2 torsional vibrations (see central inset) and are the experimental signature of the \({{{{{{\rm{SiH}}}}}^{+}_{4}}}\) species. d Shows the integrated absorption from the fine delay scan. A thresholded negative exponential fit reveals the induction time to be 11 ± 3.4 fs.
