A combination of Car-Parrinello molecular dynamics (CP-MD) and high-level ab initio quantum chemical calculations has been used to calculate the electronic absorption spectrum of formamide at finite temperatures. Thermally broadened spectra have been obtained by averaging over a large number of single-point multireference configuration interaction excitation energies calculated for geometries s...

We show that the third-order optical response of disordered linear J-aggregates can be calculated by considering only a limited number of transitions between (multi-) exciton states. We calculate the pump-probe absorption spectrum resulting from the truncated set of transitions and show that, apart from the blue wing of the induced absorption peak, it agrees well with the exact spectrum.

A new microspectroscopic technique was applied to the analysis of occluding deposits in xylem elements of Quercus serrata. The production of this substance is believed to be a defense response of the sapwood against fungal infection. An occluding substance about 10 μm across was analyzed by Infrared-Scanning Near-field Optical Microscopy (IR-SNOM), which allows for the measurement of IR spectru...

The phonon-assisted interband optical absorption spectrum of silicon is calculated at the quasiparticle level entirely from first principles. We make use of the Wannier interpolation formalism to determine the quasiparticle energies, as well as the optical transition and electron-phonon coupling matrix elements, on fine grids in the Brillouin zone. The calculated spectrum near the onset of indi...

Recent studies have suggested that a two-photon Lyman alpha driven absorption mechanism in H2 or H + 2 is responsible for the diffuse interstellar absorption bands. This hypothesis differs radically from previous theories on the origin of the diffuse interstellar bands. In order to test the validity of the H+2 hypothesis, a study is undertaken to calculate the exact properties of the H+2 spectr...

changed under ambient condition for at least 40 h, time to which these measurements were carried out. To investigate the absorption behavior as a function of time, the absorption spectrum at 100 OC was taken at regular intervals over 40 h for poled/cured A204/DR1. An absorption peak at A, , = 508 nm existed before poling/curing. After poling/curing &shifta to 493 nm with a decrease of absorbanc...

Seventeen two-photon transitions for neon have been observed in the 580- 635 nm spectral region for use in the spectroscopic study of its higher excited levels, which are not accessible by one-photon absorption. To compare the two and one-photon absorption signals originating from the same lower level, an effort was made to record single-photon optogalvanic spectrum in the available wavele...

in this research, structural and electronic properties of zncdn-1ten clusters (n=1-10) have been studied by formalism of density functional theory and using the projector augmented wave within local density approximation. the structural properties (such as bond length/angle and coordination number), electronic and optical properties (such as binding energy, kohn-sham spectrum and partial charge...

Anharmonic effects of the absorption and fluorescence spectra of pyridine molecule are studied and analyzed for the two-low lying singlet excited states S(1)((1)B(1)) and S(2)((1)B(2)). The complete active space self-consistent field (CASSCF) method is utilized to compute equilibrium geometries and all 27 vibrational normal-mode frequencies for the ground state and the two excited states. The p...

Determination of the absorption spectra of pure preparations of Northrop's crystalline pepsin inactivated by irradiation with ultra-violet light shows that the total absorption in the ultra-violet region of the spectrum increases with the degree of inactivation. This increase is especially marked between 2400 and 2750 A.u. The rate of photoinactivation is shown to be sensitive to changes in pH,...