Oxalate geometry and vibrational modes. (a) Oxalate equilibrium conformation. Green and blue arrows represent the transition dipole moment direction for each carboxylate asymmetric stretch. (b) Symmetric (b1, b2) and asymmetric (b3, b4) stretch vibrational modes. The atomic displacements are indicated with black arrows.
Experimental linear IR spectra. (solid line, upper scale) and (red dashed line, lower scale) in D2O.
Pump-probe dynamics of oxalate at 1550 cm−1. (a) Photo-induced transient signal (black filled squares) and biexponential fit (red line). (b) Anisotropy signal (black filled squares) and exponential fit (red line).
Experimental 2D IR vibrational echo spectra of oxalate in D2O for population times T = 0 fs, T = 400 fs, T = 1200 fs, and T = 2000 ps.
Potential of mean force computed for oxalate. The shaded area shows the distribution of states at 300 K.
Coupling constant of oxalates for different levels of theory. The solid, solid with filled squares, and dashed lines represent the coupling constant predicted by TDC, TCC, and DFT, respectively.
Slope S(T) versus population time for oxalate (filled squares). The smooth lines are the fits corresponding to Eq. (12) using the parameters given in the text.
Autocorrelation of the frequency fluctuations for different mechanisms, and the normalized distribution of their fluctuations. Time correlation function considering (a) only coupling between states and (b) pure solvation dynamics. Filled squares are the FFCF and the solid line is the fit of the correlation function with function given in the text. (c) Distribution function of the frequency fluctuations due to coupling (red line) and solvation dynamics (black line).
Time dependence of the population Pn. Dashed and solid lines represent the time evolution of the site populations. Squares and circles show the time dependence of the populations of the |+〉 and |−〉 exciton states. In both cases the system is initially prepared by preparing the population in a pure site or exciton state.
Linear IR spectra of oxalate. (a) The black line is the experimental absorption line shape and the red line is predicted one as discussed in the text relating to Eq. (9). (b) Modeled FTIR spectrum with different component in the FFCF: only lifetime (black line), lifetime and fluctuations in dihedral angle and hydration shell dynamics (dash red line), and lifetime, transition dipole, and fluctuations in dihedral angle and hydration shell dynamics (blue line).
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