  Photosystem II is crucial for life on Earth as it provides oxygen as a result
of photoinduced electron transfer and water splitting reactions. The excited
state dynamics of the photosystem II-reaction center (PSII-RC) has been a
matter of vivid debate because the absorption spectra of the embedded
chromophores significantly overlap and hence it is extremely difficult to
distinguish transients. Here, we report the two-dimensional
electronic-vibrational spectroscopic study of the PSII-RC. The simultaneous
resolution along both the visible excitation and infrared detection axis is
crucial in allowing for the character of the excitonic states and interplay
between them to be clearly distinguished. In particular, this work demonstrates
that the mixed exciton-charge transfer state, previously proposed to be
responsible for the far-red light operation of photosynthesis, is characterized
by the Chl$_{\rm D1}^+$Phe$^-$ radical pair and can be directly prepared upon
photoexcitation. Further, we find that the initial electron acceptor in the
PSII-RC is Phe, rather than P$_{\rm D1}$, regardless of excitation wavelength.
