Figure 4

(a) Eliashberg spectral \(\alpha ^2F(\omega )\) and (b) \(D_{cp}(\omega ,T_c)\) functions of \(\hbox {H}_3^{32}\hbox {S}\), \(\hbox {H}_3^{33}\hbox {S}\), \(\hbox {H}_3^{34}\hbox {S}\) and \(\hbox {H}_3^{36}\hbox {S}\) calculated at 180 GPa (arrows show as Eliashberg function smooths as isotope mass increases). The inset in (a) presents the \(\alpha ^2F(\omega )\) function from 80 to 220 meV. Note only changes in \(\alpha ^2F(\omega )\) are observed in the energy range of 10–70 meV.