Figure (a) shows a plot of imaginary permittivity as a function of DMABN concentration in 1,4-dioxane. Using the slope of the linear fit, equation (9), and a θ of 33.4 ps, we found the ground-state dipole moment of DMABN to be 6.2 D. This is in close agreement with the ground-state value for DMABN reported by Warman using TRDL: 6.6 D. This result demonstrates the accuracy and precision with which we can measure the ground-state dipole moment of a molecule in solution using our instrument and data analysis methods, and validates the calculations used to determine θ (described in the Molecular Rotation section of the SI). Here, the real (blue) and imaginary (red) components of the of the transient change in permittivity are separated using the procedure described in the Fitting COMSOL Models to Data and the Complex K-Factor section of our SI, giving quantitative values for ∆ε r . Notably, the noise level here is ∼100 ppb in ε r after averaging fewer than 100 laser shots (limited by the photostability of DMABN). The transient kinetics observed are similar to that reported by Warman when taking into account the differences in instrument response. Indeed, the kinetics are fit using an identical model to that employed by Warman, with certain key parameters fixed from his prior work: sequential conversion of the LE+ICT singlet to the triplet state in competition with ground-state recovery. The black traces in Figure (b) show the kinetic trajectories assigned to the singlet (solid) and triplet (dashed) states. The conversion between the singlet and triplet states takes place too fast (∼ 10 10 s -1 ) for a TRDL experiment to properly constrain the kinetic fit, and we use TRPL results from the literature to fix this timescale in our model. Likewise, the TRDL experiment does not directly observe conversion of the singlet LE and ICT states to the ground-state in competition with intersystem crossing, and we fix the triplet yield based on prior results as well. Thus, the only free fit parameters in our global kinetic model (over real and imaginary signals) is the triplet state lifetime and the change in ε r per molecule. The rate constants associated with each state are summarized in (see Supplementary Table ), and the extracted values for the transient dipole moments for the ground, singlet, and triplet excited-states are summarized in table 1. In agreement with the previous literature: (1) the singlet state of DMABN is dominated by the large dipole moment associated with the ICT state in 1,4-dioxane, and (2) the obtained triplet state dipole is substantially less than that of the singlet state. The relatively weaker agreement (relative to literature) in the absolute excited-state dipole moments we calculate compared to the ground-state most likely arises from the difficulty in ascertaining the excited-state concentration, both in our case and in past measurements. Since the calculation of the transient dipole moment is coupled to the excited-state solute concentration, the accuracy of estimating this concentration introduces error into the resultant dipole value in cases such as this where much of the dynamics are instrument-response limited. Warman et. al. relied on internal actinometry for estimating the excited-state concentration and parallel TRPL measurements to fix kinetic parameters that were not measurable via TRDL. We use careful calibration of light absorption in our EPR-tube sample configuration and excited-state density simulations that account for saturable absorption effects [discussed in section Excitation Density Calculations in the SI]. Additionally, we observed sample degradation from laser excitation, which was minimized but possibly not eliminated, by handling all samples in a nitrogen glove box, limiting our analysis to averaging the first 100 transients, and refreshing sample intermittently throughout the measurement. The good agreement we obtain for the singlet state shows that these methods are effective, but the rather large discrepancy for the triplet dipole moment measurement suggests that the triplet yield may be substantially lower in our hands than the value found previously, which is fixed in our kinetic model at the literature value.