The light-harvesting efficiency of a photoactive molecular complex is largely
determined by the properties of its electronic quantum states. Those, in turn,
are influenced by molecular vibrational states of the nuclear degrees of
freedom. Here, we reexamine two recently formulated concepts that a coherent
vibronic coupling between molecular states would either extend the electronic
coherence lifetime or enhance the amplitude of the anticorrelated vibrational
mode at longer times. For this, we study a vibronically coupled dimer and
calculate the nonlinear two-dimensional (2D) electronic spectra which directly
reveal electronic coherence. The timescale of electronic coherence is initially
extracted by measuring the anti-diagonal bandwidth of the central peak in the
2D spectrum at zero waiting time. Based on the residual analysis, we identify
small-amplitude long-lived oscillations in the cross-peaks, which, however, are
solely due to groundstate vibrational coherence, regardless of having resonant
or off-resonant conditions. Our studies neither show an enhancement of the
electronic quantum coherence nor an enhancement of the anticorrelated
vibrational mode by the vibronic coupling under ambient conditions