Search results for "EXCITATION"
showing 10 items of 1290 documents
Ultrafast excitation dynamics of low energy pigments in reconstituted peripheral light-harvesting complexes of photosystem I
2000
AbstractUltrafast dynamics of a reconstituted Lhca4 subunit from the peripheral LHCI-730 antenna of photosystem I of higher plants were probed by femtosecond absorption spectroscopy at 77 K. Intramonomeric energy transfer from chlorophyll (Chl) b to Chl a and energy equilibration between Chl a molecules observed on the subpicosecond time scale are largely similar to subpicosecond energy equilibration processes within LHCII monomers. However, a 5 ps equilibration process in Lhca4 involves unique low energy Chls in LHCI absorbing at 705 nm. These pigments localize the excitation both in the Lhca4 subunit and in LHCI-730 heterodimers. An additional 30–50 ps equilibration process involving red …
Torsional shear strength and elastic properties of adhesively bonded glass-to-steel components
2020
Nowadays glass is widely used in building applications and coupled to steel through adhesive joining. Reliable mechanical characterization of these joints is necessary to design and predict the final structure performance.In this framework, the aim of this paper is to measure the pure shear strength and elastic modulus for design and modelling of adhesive joined glass-to-steel structures.Torsional shear strength and elastic properties of an adhesively bonded glass-to-steel component were measured on several joined steel-to-steel and steel-to-glass samples.An epoxy resin-based adhesive was used as joining material for AISI304 steel and soda-lime glass.The same steel and adhesive were used to…
Fractional frequency collective parametric resonances of an ion cloud in a Paul trap
1998
ion cloud ina Paul trap driven at simple fractions of twice the secular frequency of the trap by an additionally appliedquadrupole field. The fractional resonances are observable only if the excitation field surpasses a criticalstrength. Odd-even staggering of the thresholds is observed.@S1050-2947~98!51307-8#PACS number~s!: 32.80.Pj, 07.75.1h
Exciton emission and defect formation in yttrium trifluoride
2005
Two intrinsic emission bands at 220 and 280 nm have been detected in nominally pure YF3 powders at 10 K. Excitation spectra for both emissions have a sharp peak at 12 eV near the edge of interband transition. Observed emissions are assigned to the radiative decay of self-trapped excitons in YF3. The strong thermal quenching of intrinsic luminescence was observed at temperature above 120 K. It was supposed that non-radiative decay of self-trapped exciton at high temperatures lead to defect formation in YF3. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(ii) complexes
2021
Two closely related FeII complexes with 2,6-bis(1-ethyl-1H-1,2,3-triazol-4yl)pyridine and 2,6-bis(1,2,3-triazol-5-ylidene)pyridine ligands are presented to gain new insights into the photophysics of bis(tridentate) iron(II) complexes. The [Fe(N^N^N)2]2+ pseudoisomer sensitizes singlet oxygen through a MC state with nanosecond lifetime after MLCT excitation, while the bis(tridentate) [Fe(C^N^C)2]2+ pseudoisomer possesses a similar 3MLCT lifetime as the tris(bidentate) [Fe(C^C)2(N^N)]2+ complexes with four mesoionic carbenes. Financial support from the Deutsche Forschungsge-meinschaft [DFG, Priority Program SPP 2102] "Light-controlled reactivity of metal complexes" (BA 4467/7-1, LO 714/11-1, …
Stark ionization of atoms and molecules within density functional resonance theory
2013
We show that the energetics and lifetimes of resonances of finite systems under an external electric field can be captured by Kohn–Sham density functional theory (DFT) within the formalism of uniform complex scaling. Properties of resonances are calculated self-consistently in terms of complex densities, potentials, and wave functions using adapted versions of the known algorithms from DFT. We illustrate this new formalism by calculating ionization rates using the complex-scaled local density approximation and exact exchange. We consider a variety of atoms (H, He, Li, and Be) as well as the H2 molecule. Extensions are briefly discussed.
UV photoexcitation of a dissolved metalloid Ge9 cluster compound and its extensive ultrafast response.
2015
Femtosecond pump-probe absorption spectroscopy in tetrahydrofuran solution has been used to investigate the dynamics of a metalloid cluster compound {Ge9[Si(SiMe3)3]3}(-). Upon UV photoexcitation, the transients in the near-infrared spectral region showed signatures reminiscent of excess electrons in THF (bound or quasi-free) whereas in the visible part excited state dynamics of the cluster complex dominates.
On the study of the vibrational energy levels of Arsine molecule
2008
Abstract We compare two formalisms applied to the vibrational modes of the molecule of AsH 3 of C 3 v molecular symmetry group. Indeed, the close stretching modes of this molecule may be considered as those of a three-dimensional oscillator whereas the bending modes may be considered either as a one-dimensional oscillator of symmetry A 1 and a two-dimensional oscillator of symmetry E or as an approximate three-dimensional oscillator. So, we have applied the U ( p + 1) formalism to the both stretching and bending modes and introduced coupling terms acting on an appropriate coupled vibrational basis through a local mode formalism. We have then compared the result of our fitting with those ob…
An ab initio study of the low-lying 1 A′ electronic states of indene
1999
Abstract The electronic absorption spectrum of indene in the region of the lowest-lying valence π → π * singlet excited states was studied using multi-configurational second-order perturbation theory through the CASPT2 formalism. Four 1 A′ states were found to be the most important for describing the excitation spectrum up to 6.8 eV. Their transition energies (oscillator strengths in parentheses) were computed to be: 4.46 eV (0.0004), 5.02 eV (0.175), 6.14 eV (0.221), and 6.36 eV (0.434). These states can be labelled and described as the four Platt states of indene: 1 L a , 1 L b , 1 B b , and 1 B a , respectively. This description of the spectrum explains the experimental observations bett…
Rydberg or Valence? The Long-Standing Question in the UV Absorption Spectrum of 1,1′-Bicyclohexylidene
2008
The electronic excited states of the olefin 1,1'-bicylohexylidene (BCH) are investigated using multiconfigurational complete active space self-consistent-field second order perturbation theory in its multi-state version (MS-CASPT2). Our calculations undoubtedly show that the bulk of the intensity of the two unusually intense bands of the UV absorption of BCH measured with maxima at 5.95 eV and 6.82 eV in the vapor phase are due to a single pi pi* valence excitation. Sharp peaks reported in the vicinity of the low-energy feature in the gas phase correspond to the beginning of the pi 3s(R) Rydberg series. By locating the origin of the pi pi* band at 5.63 eV, the intensity and broadening of th…