Ultrafast E to Z photoisomerization dynamics of the Cph1 phytochrome

► Broadband Transient Absorption signals resolved with global analysis. ► Homogeneous dynamics with a single relaxed excited-state lifetime. ► Rapid excited-state quenching dynamics (265 fs) of Pfr of Cph1. ► Slower vibrational relaxation (2.8 ps) of non-isomerizing population. ► Considerably faster than forward dynamics of Pr of Cph1.