  The energy transfer processes and coherent phenomena in the
fucoxanthin-chlorophyll protein complex, which is responsible for the light
harvesting function in marine algae diatoms, were investigated at 77 K by using
two-dimensional electronic spectroscopy. Experiments performed on the
femtosecond and picosecond timescales led to separation of spectral dynamics,
witnessing evolutions of coherence and population states of the system in the
spectral region of ${\rm Q}_{y}$ transitions of chlorophylls $a$ and $c$.
Analysis of the coherence dynamics allowed us to identify chlorophyll (Chl) $a$
and fucoxanthin intramolecular vibrations dominating over the first few
picoseconds. Closer inspection of the spectral region of the ${\rm Q}_{y}$
transition of Chl $c$ revealed previously not identified mutually
non-interacting chlorophyll $c$ states participating in femtosecond or
picosecond energy transfer to the Chl $a$ molecules. Consideration of separated
coherent and incoherent dynamics allowed us to hypothesize the
vibrations-assisted coherent energy transfer between Chl $c$ and Chl $a$ and
the overall spatial arrangement of chlorophyll molecules.
