Search results for "Spectroscopy"
showing 10 items of 10293 documents
Vibrational analysis of Ni(II)- and Cu(II)-octamethylchlorin by polarized resonance Raman and Fourier transform infrared spectroscopy
2001
We measured the polarized resonance Raman spectra of Cu(II)-2,2,7,8,12,13,17,18-octamethylchlorin in CS2 at various excitation wavenumbers in a spectral region covering the Qy, Qx and Bx optical absorption bands. Additionally, we measured the FTIR-Raman spectrum of the highly overcrowded spectral region between 1300 and 1450 cm−1. The spectral decomposition was carried out by a self-consistent global fit to all spectra obtained. The thus identified Raman and IR lines were assigned by comparison with the resonance Raman spectra of Cu(II)-octaethylporphyrin, by utilizing their depolarization ratio dispersions and by a normal mode analysis. The latter was based on a modified transferable molec…
Electronic structure of p-type ultraviolet-transparent conducting CuScO2 films
2008
Abstract We investigate the electronic structure of CuScO 2 thin films grown on sapphire and mica substrates by pulsed laser deposition. X-ray diffraction and microanalysis confirm that the films have the expected delafossite crystal structure and stoichiometric proportions. The electronic structure is investigated by means of X-ray and ultraviolet photoelectron spectroscopy. Electronic states in the range 0–1350 eV are identified, making reference to theoretical density-of-states calculations up to 80 eV. Photoelectron spectra near the Fermi energy confirm the p-character of the films. Optical absorption spectroscopy shows that the films are transparent up to 3.7 eV and exhibit an intense …
Photophysical behavior of 3-methylquinoline and 3-bromoquinoline
1992
Abstract The phosphorescence emission and excitation spectra and their polarizations have been studied for 3-methylquinoline and 3-bromoquinoline in methylcyclohexane and ethanol glasses at 77 K. From the results obtained in 3-methylquinoline (τp = 1.30 s in ethanol, τp = 1.05 s in methylcyclohexane and the out-of-plane polarization) it is concluded that the emission originates from a triplet state of 3ππ∗ character. In 3-bromoquinoline, the phosphorescence lifetimes (ca. 8 ms in a non-polar solvent and 15 ms in a polar solvent) and the negative degree of polarization indicate an emitting state of ππ∗ character that is strongly coupled to a higher-lying triplet state of the nπ∗ type. The mo…
Study of water adsorption and capillary bridge formation for SiO(2) nanoparticle layers by means of a combined in situ FT-IR reflection spectroscopy …
2014
Water adsorption and capillary bridge formation within a layer of SiO2-nanoparticles were studied in situ by means of a combination of quartz crystal microbalance (QCM-D) with dissipation analysis and Fourier transformation infrared reflection absorption spectroscopy (FT-IRRAS). FT-IR data were employed to distinguish the “ice-like” and “liquid-like” contributions and to support the analysis of the QCM-D data concerning mass change and dissipation. Combined measurements show that for SiO2-nanoparticles with a diameter of about 250 nm, the formation of two adsorbed monolayers of water as well as bulk water leads to a rather linear increase in the dissipation for relative humidity values of u…
Regioselective Hydrogenation of a 60-Carbon Nanographene Molecule toward a Circumbiphenyl Core.
2019
Regioselective peripheral hydrogenation of a nanographene molecule with 60 contiguous sp2 carbons provides unprecedented access to peralkylated circumbiphenyl (1). Conversion to the circumbiphenyl core structure was unambiguously validated by MALDI-TOF mass spectrometry, NMR, FT-IR, and Raman spectroscopy. UV–vis absorption spectra and DFT calculations demonstrated the significant change of the optoelectronic properties upon peripheral hydrogenation. Stimulated emission from 1, observed via ultrafast transient absorption measurements, indicates potential as an optical gain material.
Spectroscopic and quantum chemical study of pressure effects on solvated chlorophyll
2004
Abstract Hydrostatic pressure effects up to 907 MPa on absorption spectra of chlorophyll a molecules dissolved in diethyl ether have been studied at ambient temperature both experimentally and theoretically using quantum chemistry methods. The fluorescence spectra are studied only experimentally. The data suggest that coordination interactions between the central Mg atom of the chlorophyll and solvent molecules along with interactions that modify the porphyrin skeleton of the solute are responsible for the observed differences of pressure dependence of the Q y , Q x , and Soret spectral bands. The coordination number of the Mg atom changes from five to six between 400 and 600 MPa.
Detection of 4T1(P) quartet of Co2+ in Zn99.95Co0.05Se monocrystal by optical absorption spectroscopy
2003
Abstract Optical absorption spectra of Zn 99.95 Co 0.05 Se were recorded at 25 K. The thickness and the concentration of cobalt were adjusted to obtain sharp d–d ∗ transitions of Co 2+ corresponding not only to multiplets of 4 T 1 (P) but also to higher excited states. For the first time, a very weak quartet splitting of 4 T 1 (P) state was clearly observed and these states were located between 1.464 and 1.517 eV. Higher series of energy states were found to lie in the range 1.98–2.108 eV which are expected on the basis of theoretical calculations but were not detected before and they were tentatively assigned to a lower multiplet of 2G configuration of free ion. The next series of transiti…
Ab Initio Studies of Triplet-State Properties for Organic Semiconductor Molecules
2012
Triplet–triplet annihilation (TTA) leads to a reduced efficiency of organic light-emitting diodes (OLEDs) at high current densities. Spacial confinement of the triplet excitons, which is mainly dependent on triplet energy differences, can reduce the TTA rate. Therefore, a deliberate choice of the organic semiconductor materials with particular attention to their triplet energies can help to considerably increase the device efficiency. Organic solid-state lasers are, on the other hand, efficiently quenched by singlet–triplet annihilation (STA), which is closely related to the triplet–triplet absorption of the organic semiconductors. To establish a useful set of parameters related to the proc…
On nature of the transient IR-absorption STE-like bands at 0.15–0.36eV in alkali halides
2001
New evidence is given that two classes (A and B) of the transient IR-absorption bands: (A) with max. at 0.15-0.36 eV (in NaCl : I, NaBr, NaI, KCl : I, KBr : I, RbCl : I, RbBr : I), due to on-centre self-trapped exciton and (B) with max. at 0.27-0.36 eV (in NaCI, KCl, KBr, RbCl), due to shallow trapped electrons or bound polarons, are caused by the same defect-shallow trapped electron (e-) at the substitutional (cation: c-site) alkali impurity cation (M + ): [M - ] 0 c e - . The A- and B-class IR bands have the same location, similar shape, half-width (exactly coincide for KCl : I and KCl at 80 or 10 K with the same vibration structure). It is established that the same Mollwo-Ivey plot curve…
Intramolecular charge transfer and enhanced quadratic optical non-linearities in push pull polyenes
1997
Abstract Push-pull polyenes, which have an electron-donating group (D) and an electron-withdrawing group (A) grafted on opposite ends of a conjugated polyenic chain, are of particular interest as model compounds for long-distance intramolecular charge transfer (ICT), as well as potent non-linear optical chromophores. Several series of push-pull polyenes of increasing length, combining aromatic donor moieties and various acceptor groups, have been prepared and studied. Their linear and non-linear optical properties have been investigated by performing electro-optical absorption measurements (FOAM) and electric-field-induced second-harmonic generation (EFISH) experiments in solution. Each mol…