Near-resonant absorption in the time-dependent self-consistent field and multiconfigurational self-consistent field approximations

Abstract

The linear response function has been derived and implemented in the time-dependent self-consistent field and multiconfigurational self-consistent field approximations with consideration made for the finite lifetimes of the electronically excited states. Inclusion of damping terms makes the response function convergent at all frequencies including near-resonances and resonances. Applications are the calculations of the electric dipole polarizabilities of hydrogen fluoride, methane, trans-butadiene, and three push–pull systems. The polarizability is complex with a real part related to the refractive index and an imaginary part describing linear absorption. The relevance of linear absorption in nonlinear optics is effectively expressed in terms of figures-of-merit. Such figures-of-merit have been calculated showing that the nonresonant linear absorption must be considered when the nonlinear optical quality of a material is to be assessed.

Unraveling the similarity of the photoabsorption of deprotonated p-coumaric acid in the gas phase and within the photoactive yellow protein

“…It can be seen that the errors introduced by the QM/MM partitioning are essentially negligible. It is also noteworthy that for the pCTM -+Cys69 system, the QM/MM and QM 40 calculations give identical results, although the Cα-Cβ bond is cut only in the QM/MM approach.…”

“…18 at the DFT(B3LYP)/6-31+G* level. We also calculated the force field using the 40 larger and more flexible aug-cc-pVDZ basis set, but that led to negligible changes in the final prediction of the excitation energies and are not presented here. All calculations of the force field were performed with the Molcas 7.4 quantum chemistry program.…”

“…In particular, pCA has a trans double bond and is deprotonated (pCA -) in the electronic ground state of PYP. 5 At the heart of cellular response to radiation lies the concept of electronic transitions most easily visualized in 40 terms of electronic excitation energies. Essentially, the characteristics of a photoactive protein may be explained by considering the electronic structure of the chromophore; it reflects the frequency interval in which the action of the holoprotein is needed: It is only when the chromophore 45 absorbs light of a suitable wavelength that structural changes in the protein occur and are followed by appropriate action from the host cell.…”

“…10 to show that the effect of Arg52 on the energetics of the S 0 ⇒S 1 transition is negligible, although it provides a stabilization with respect to autoionization. Another check of 40 the validity of the reported excitation energies and oscillator strengths is through the use of damped response theory. 40 Here the absorption is determined directly.…”

“…Another check of 40 the validity of the reported excitation energies and oscillator strengths is through the use of damped response theory. 40 Here the absorption is determined directly. This allows us to calculate an absorption spectrum in a direct way, circumventing the troublesome metastable state.…”