Search results for "Triplet"
showing 10 items of 159 documents
Optically Detected Magnetic Resonance of Chlorophyll Triplet States in Water-Soluble Chlorophyll Proteins from Lepidium virginicum: Evidence for Exci…
2018
Optically detected magnetic resonance of triplet states populated by photoexcitation in water-soluble chlorophyll proteins (WSCPs) from Lepidium virginicum has been performed using both absorption and fluorescence detection. Well resolved triplet-singlet (T-S) spectra have been obtained and interpreted in terms of electronic interactions among the four chlorophylls (Chls), forming two dimers in the WSCP tetramer. Localization of the triplet state on a single Chl leads to a redistribution of the oscillator strength in the remaining three Chls of the complex. By comparing the spectra with those obtained on a substoichiometric WSCP complex containing only 2 Chls per protein tetramer, we proved…
Probing the electronic state of a single coronene molecule by the emission from proximate fluorophores.
2012
We measured electronic transitions of the 2D graphene-type molecule hexa-peri-hexabenzocoronene (HBC) at the single-molecule level. The large intersystem crossing rate and long triplet state lifetime in the range of seconds are prohibitive for direct single-molecule observation. By covalently coupling fluorescent acceptor molecules (perylenecarboximide, PMI) to HBC, efficient singlet energy transfer gives rise to strong PMI fluorescence. Confocal single-molecule fluorescence microscopy with two excitation colours matching the HBC and PMI transition frequencies, respectively, was conducted. Single HBC-6PMI molecules were readily observed via the PMI emission. It was found that after selectiv…
Machine learning techniques demonstrating individual movement patterns of the vertebral column: the fingerprint of spinal motion
2022
Surface topography systems enable the capture of spinal dynamic movement; however, it is unclear whether vertebral dynamics are unique enough to identify individuals. Therefore, in this study, we investigated whether the identification of individuals is possible based on dynamic spinal data. Three different data representations were compared (automated extracted features using contrastive loss and triplet loss functions, as well as simple descriptive statistics). High accuracies indicated the possible existence of a personal spinal 'fingerprint', therefore enabling subject recognition. The present work forms the basis for an objective comparison of subjects and the transfer of the method to…
Optical properties of Ge-oxygen defect center embedded in silica films
2007
The photo-luminescence features of Ge-oxygen defect centers in a 100nm thick Ge-doped silica film on a pure silica substrate were investigated by looking at the emission spectra and time decay detected under synchrotron radiation excitation in the 10-300 K temperature range. This center exhibits two luminescence bands centered at 4.3eV and 3.2eV associated with its de-excitation from singlet (S1) and triplet (T1) states, respectively, that are linked by an intersystem crossing process. The comparison with results obtained from a bulk Ge-doped silica sample evidences that the efficiency of the intersystem crossing rate depends on the properties of the matrix embedding the Ge-oxygen defect ce…
Formation, Detection and Trapping of Photoassociated Ultracold KRb Molecules
2005
Ultracold ground-state KRb molecules are formed by photoassociation and detected by resonant two-photon ionization. We have assigned both the photoassociation spectrum and the detection laser spectrum, and we have demonstrated magnetic trapping of triplet KRb
Spin dependence of low energy charge exchange between H 2 + and Na
1987
The difference in charge exchange rate in collisions between spin oriented sodium atoms and H 2 + ions has been measured at an energy of about 1 eV. H 2 + was stored in a Penning trap and polarized by spin exchange with Na beam atoms from a hexapole magnet. The ion loss from the trap due to charge exchange was different as we depolarized the atomic beam. From the data we obtain a ratio of cross sections for singlet and triplet collisionsQ 1/Q 3=1.5±0.2 andQ 3=1.2·10−15 cm2.
Luminescence of a self-trapped exciton in GeO2 crystal
1993
Abstract The self-trapped exciton (STE) is discovered in the GeO2 crystal. A PL band at 2.5 eV with a strong Stokes shift is excited only in the fundamental absorption range of GeO2 crystal with the quantum yield about 0.4 and the decay time constant 800 ± 5 μs at 80 K. The PL thermal quenching occurs at 200 K with the energy about 0.25 eV and the frequency factor 107. At 4.5 K the PL decay kinetics splits into two components with time constants 270 μs and 8000 μs, which can be due to a triplet state split in the zero magnetic field. The STE in GeO2 is very similar to a STE in SiO2.
Ultrafast decay of the excited singlet states of thioxanthone by internal conversion and intersystem crossing.
2010
The experimental ultrafast photophysics of thioxanthone in several aprotic organic solvents at room temperature is presented, measured using femtosecond transient absorption together with high-level ab initio CASPT2 calculations of the singlet- and triplet-state manifolds in the gas phase, including computed state minima and conical intersections, transition energies, oscillator strengths, and spin-orbit coupling terms. The initially populated singlet pi pi* state is shown to decay through internal conversion and intersystem crossing processes via intermediate n pi* singlet and triplet states, respectively. Two easily accessible conical intersections explain the favorable internal conversio…
Calculation of frequency-dependent hyperpolarizabilities using general coupled-cluster models.
2007
By exploiting the similarities between response theory and analytic derivative theory, we present a scheme for calculating frequency-dependent hyperpolarizabilities at the coupled-cluster level within the framework for analytic third derivatives. This has been implemented for arbitrary levels of coupled-cluster theory up to the full-configuration-interaction limit. An investigation of some small molecules shows that the inclusion of triple excitations is essential for an accurate description of hyperpolarizabilities.
Perturbative calculation of spin-orbit splittings using the equation-of-motion ionization-potential coupled-cluster ansatz.
2008
Spin-orbit splittings for (2)Pi states are calculated within coupled-cluster (CC) theory via first-order degenerate perturbation theory. Using the equation-of-motion CC variant for ionization potentials (EOMIP-CC), the two components of the considered (2)Pi state are treated in a balanced way by generating both radical states via annihilation of one electron out of the CC wave function of the corresponding anion. We report on the implementation of the described approach within the CC singles and doubles approximation. To ensure computational efficiency, an atomic mean-field approximation for the spin-orbit integrals is used, resulting in a formulation in terms of one-electron transition-den…