Molecular hyperpolarizabilities of coumarin dyes

Surface-Assisted Transient Displacement Charge Technique. I. Photoinduced Charge Transfer in Self-Assembled Monolayers

“…Presuming the same <Δμ ⊥ > for the triplet excited state, the estimated yield was approximately 4%, which reasonably agrees with the reported triplet yields for aminocoumarins. 20,22,25,26 …”

“…From Equation (15) the dipole signal in PTDC under conditions of fast molecular rotation is proportional to the change of dipole moment squared: (17) For calculating the dipole signal, i.e. the voltage drop across the load resistor, one needs to calculate the charge at the electrodes, Q, which is given by the product of displacement, D, and the electrode area, S, normalized by 4π: (18) If presumed uniform, the electric field inside the cell, E, is given by the voltage drop across the cell, v cell , divided by the cell gap, d: (19) Then the voltage, v, measured across the load resistor, R, arises from the displacement current: 1,17 (20) After substituting E from Equation (19) and using v = -v cell (in standard PTDC v = V 0 -v cell , with V 0 being is applied voltage), one obtains the time variation of the dipole signal, v: (21) Here the RC time of the circuit is introduced: (22) It is obvious from the derivation that Equation (21) is identical for both, the standard PTDC and the surface assisted PTDC techniques. The difference is in how the solute polarization, P solute , is calculated: compare Equation (13) and.…”

Solute location in a nanoconfined liquid depends on charge distribution

“…In particular, it possesses a charge transfer electronic transition that increases its dipole moment from 6 D in the ground state to 13 D in the excited state. [26][27][28] In previous simulations, we have shown that ground-state C153 is preferentially localized at the pore interface. 29 Here, we compare those results to simulations of the excited-state solute.…”

“…The final system used in all simulations consists of 121 ethanol molecules and 1 C153 molecule all contained within a 44 × 30 × 40 Å 3 simulation box. Atomistic models for C153 were taken from the work of Maroncelli et al 38 The ground-and excited-state parameters differ only in the atomic charges, giving µ g = 6 D and µ e = 13 D. [26][27][28] Replica exchange molecular dynamics 39 (REMD) simulations for the excited-state C153 were carried out using LAMMPS 40 at 20 different temperatures for a total of 150 ns after a 5 ns equilibration. The results are compared to those for ground-state C153 from a 100 ns simulation, reported previously, 29 to explore the electronic state dependence.…”

Surface-Assisted Transient Displacement Charge Technique. II. Effect of Gases on Photoinduced Charge Transfer in Self-Assembled Monolayers

“…2 It is even greater in the gas phase. 3 As Figure 4 illustrates, the average projection, <cos 2 θ>, calculated from the absorption intensities parallel, A ∥ , and perpendicular, A ⊥ , to the surface: 2,3 (6) is much lower in the gas phase (<cos 2 θ> = 0.18) than in any solvent. If the distribution were reduced to a single angle, θ av , that angle would be almost 65° from the normal to the surface.…”