= M. C. Asplund
{c}
<M. C. Asplund> is a coauthor of the primary phase-controlled peptide experiment in <two-dimensional infrared spectroscopy>. The published paper identifies a University of Pennsylvania chemistry affiliation and retains the exact byline M. C. Asplund, alongside M. T. Zanni and R. M. Hochstrasser.<Two-dimensional infrared spectroscopy of peptides by phase-controlled femtosecond vibrational photon echoes by M. C. Asplund and others>[Author byline and affiliation.]{ref}
The joint experiment measured phase and amplitude of <vibrational photon echoes> and resolved features interpreted as coupling between amide-I modes. It connected controlled pulse delays with information about molecular interactions.<Two-dimensional infrared spectroscopy of peptides by phase-controlled femtosecond vibrational photon echoes by M. C. Asplund and others>[Abstract, coupled modes and phase-sensitive measurement.]{ref}
An original response-matrix example clarifies the extra question asked by a multidimensional experiment. Consider two stipulated maps
$$
S_1=\begin{pmatrix}1&0\\0&1\end{pmatrix},\qquad
S_2=\begin{pmatrix}1&0.2\\0.2&1\end{pmatrix}.
$$
Their diagonal values agree, while their off-diagonal responses differ. Looking only at the two diagonal amplitudes would miss that difference. These are illustrative spectral-response entries, not quantum density matrices or reported experimental data.
A <2D IR cross peak> can supply a constraint on relationships between vibrations, but its cause must be assessed using the signal phase, timing and physical model. <M. C. Asplund>'s verified contribution is coauthorship of that experimental method; the paper does not by itself assign every individual apparatus or analysis task to one coauthor.
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