This work presents theory, implementation, and validation of excited state properties obtained from time-dependent density functional theory (TDDFT). Based on a fully variational expression for the excited state energy, a compact derivation of first order properties is given. We report an implementation of analytic excited state gradients and charge moments for local, gradient corrected, and hybrid functionals, as well as for the configuration interaction singles (CIS) and time-dependent Hartree–Fock (TDHF) methods. By exploiting analogies to ground state energy and gradient calculations, efficient techniques can be transferred to excited state methods. Benchmark results demonstrate that, for low-lying excited states, geometry optimizations are not substantially more expensive than for the ground state, independent of the molecular size. We assess the quality of calculated adiabatic excitation energies, structures, dipole moments, and vibrational frequencies by comparison with accurate experimental data for a variety of excited states and molecules. Similar trends are observed for adiabatic excitation energies as for vertical ones. TDDFT is more robust than CIS and TDHF, in particular, for geometries differing significantly from the ground state minimum. The TDDFT excited state structures, dipole moments, and vibrational frequencies are of a remarkably high quality, which is comparable to that obtained in ground state density functional calculations. Thus, yielding considerably more accurate results at similar computational cost, TDDFT rivals CIS as a standard method for calculating excited state properties in larger molecules.

Adiabatic time-dependent density functional methods for excited state properties

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

A two-dimensional (2D) correlation method generally applicable to various types of spectroscopy, including IR and Raman spectroscopy, is introduced In the proposed 2D correlation scheme, an external perturbation is applied to a system while being monitored by an electromagnetic probe With the application of a correlation analysis to spectral intensity fluctuations induced by the perturbation, new types of spectra defined by two independent spectral variable axes are obtained Such two-dimensional correlation spectra emphasize spectral features not readily observable in conventional one-dimensional spectra While a similar 2D correlation formalism has already been developed in the past for analysis of simple sinusoidally varying IR signals, the newly proposed formalism is designed to handle signals fluctuating as an arbitrary function of time, or any other physical variable This development makes the 2D correlation approach a universal spectroscopic tool, generally applicable to a very wide range of applications The basic property of 2D correlation spectra obtained by the new method is described first, and several spectral data sets are analyzed by the proposed scheme to demonstrate the utility of generalized 2D correlation spectra Potential applications of this 2D correlation approach are then explored

Generalized Two-Dimensional Correlation Method Applicable to Infrared, Raman, and other Types of Spectroscopy:

Photo-, thermo-, solvato-, and electrochromic spiroheterocyclic compounds.

Carbon nanotubes due to their specific atomic structure have interesting chemical and physical properties according to those of graphite and diamond. This review covers the characterization methods of carbon nanotubes which are most employed today. The structure of carbon nanotubes is first briefly summarized followed by a description of the characterization methods such as STM, TEM, neutron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy, infrared and Raman spectroscopy. The most interesting features are indexed for each technique.

Characterization methods of carbon nanotubes : a review.

Raman studies of carbon nanotubes

Journal of molecular structure

One-electron photoreduction of flavin mononucleotide: time-resolved resonance Raman and absorption study

Submicrosecond time-resolved infrared study on the structure of the photoinduced transient species of salicylideneaniline in acetonitrile

Transient resonance Raman and absorption spectra of the anion radical CM•- and lowest excited triplet state 3CM* of coumarin were measured. Vibrational assignments of the ground state S0, CM•-, and 3CM* were performed based on both the frequency shifts on isotopic (18O, 13C, and deuterium) substitutions and normal-coordinate calculations using the force constants obtained by ab initio molecular orbital computations. The vibrational assignments and ab initio MO calculations provided much information on the structures of S0, CM•-, and 3CM*. It is concluded that the C(3)C(4) bond of the pyrone ring is lengthened markedly in CM•- and drastically in 3CM*. This suggests that the C(3)C(4) bond is one of the reactive sites of coumarin and furocoumarins in their photochemical reactions, which is in good accord with the formation of cyclobutane-type adducts with pyrimidine bases, particularly with thymine, through the C(3)C(4) bond of furocoumarins and the C(5)C(6) bond of pyrimidine bases. The CO bond was found to...

Transient Resonance Raman and ab Initio MO Calculation Studies of the Structures and Vibrational Assignments of the T1 State and the Anion Radical of Coumarin and Its Isotopically Substituted Analogues

Hiroaki Takahashi

Papers

Raman studies of carbon nanotubes

Journal of molecular structure

One-electron photoreduction of flavin mononucleotide: time-resolved resonance Raman and absorption study

Submicrosecond time-resolved infrared study on the structure of the photoinduced transient species of salicylideneaniline in acetonitrile

Transient Resonance Raman and ab Initio MO Calculation Studies of the Structures and Vibrational Assignments of the T1 State and the Anion Radical of Coumarin and Its Isotopically Substituted Analogues