Spin Singlet and Triplet State

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Electric-Field-Induced Triplet to Singlet Transition in Size-2 Trigonal Zigzag Graphene Nanoflake

Electric-Field-Induced Triplet to Singlet Transition in Size-2 Trigonal Zigzag Graphene Nanoflake

Since d 11 = − d 22 , the quantity E d . 11 + E d . 22 is eqal to zero (see Table 1). This means that the external electric field dose not couple to the magnetic triplet state of size-2 NF directly, and the major part of polarization energy and electric dipole moment of the magnetic triplet state must be due to the core states. For the spin singlet states the situation is different. The external in plane electric field mixes the three spin singlet states and the effective Hamiltonian including the in plane electric field has the form

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Synthesis and characterization of triangulene

Synthesis and characterization of triangulene

The energy of the (ferromagnetic) triplet state was calculated by performing unrestricted spin-polarised energy minimization. To select the (antiferromagnetic) open-shell singlet state two spatially separated initial magnetic moments of opposing sign were defined. To select the (nonmagnetic) closed-shell singlet state the spin of the entire unit cell was constrained to a spin multiplicity of one or spin-unpolarised calculations were performed. In all cases the geometry was optimized independently until the atomic force components per atom converged to less than 10 −4 eV/Å.

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Magnetic Field Effects on Molecular Emissivity in Solutions

Magnetic Field Effects on Molecular Emissivity in Solutions

Magnetic control over excited states of molecules presents interest for many applications. Here we show for the first time that visible room temperature phosphorescence in multichromophoric donor-acceptor systems can be modulated by weak magnetic fields (<1 Tesla) via Magnetic Field Effects (MFE) on the spin dynamics in photo-generated radical pairs (RP). The studied compounds comprise Pt porphyrin (PtP)-Rosamine B (RosB) dyads, which possess strong visible absorption bands and phosphoresce at room temperature. The observed MFE is unique in that it occurs upon direct excitation of the PtP in the dyads, whereby ultrafast quantitative formation of the local PtP triplet state precedes occurrence of radical intermediates. A model explaining the effect is proposed, which is based on reversible electron transfer between the local triplet state and a long-lived RP. External magnetic field modulates spin dynamics of the RP, affecting contribution of the singlet RP recombination channel and thereby influencing phosphorescence.

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Magnetophotoluminescence of negatively charged excitons in narrow quantum wells

Magnetophotoluminescence of negatively charged excitons in narrow quantum wells

the symmetrical spin wave function correspond to the triplet state of the negatively charged exciton, X t ⫺ . By applying a magnetic field, the degeneracy of the energy levels of X s ⫺ and X t ⫺ is lifted by the Zeeman interaction determined by the exciton gyromagnetic ratio (g factor 兲 . Much theoretical ef- fort has been put into predicting the field dependence of these states. There is now a consensus that the triplet state is unbound at low fields, while the singlet is bound at any field. 共 A recent theory has predicted that the triplet will be stable at zero field, 3 but this has not yet been observed experimen- tally. 兲 A source of great debate has been the lowest-energy bound triplet, which is not expected to be observable experi- mentally in two-dimensional 共 2D 兲 systems, 4 and is therefore called the ‘‘dark’’ triplet. Despite this, a number of experi- ments by different groups have shown a clear triplet transi- tion for 2D QW spectra at finite field. 7–13 Recently, this ap- parent contradiction was resolved by the theoretical discovery of a new optically active ‘‘bright’’ triplet state, 2 which should be seen experimentally. This has motivated us to perform new experiments with polarization sensitivity on a series of samples and to make a fresh comparison between theory and experiment.

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Effects of charge noise on a pulse gated singlet triplet S−T− qubit

Effects of charge noise on a pulse gated singlet triplet S−T− qubit

it is ramped back to the initial value, where it is held long enough for the spin state to be measured and reset. When the ramp rate is appropriate, the first ramp leads to occupation of both states with a relative phase that accumulates at large detuning during the manipulation time, and ramping back to (2,0) gives rise to Landau- Zener-St¨ uckelberg (LZS) oscillations. The probability of being in the singlet state at the end of the sequence os- cillates as a function of τ s , as shown in the inset of Fig. 3

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Exploring Molecular Electronic Structure Through Donor-Bridge-Acceptor Biradicals.

Exploring Molecular Electronic Structure Through Donor-Bridge-Acceptor Biradicals.

Figure II-13. Calculated pure singlet and triplet spectra of 1-MePh via VT-EAS results. ..... 57 Figure II-14. Resonance Raman stack plot of 1 (black), 1-pPh (red), 1-MePh (blue), and 1- pXylyl (green) using a 407 nm excitation............................................................................... 58 Figure II-15. Arrow pushing line bond drawing showing structure of SQ (SOMO) → NN (LUMO) CT excited state. The 1603 cm -1 stretch in the resonance Raman thus comes from the quinoidal character of the complex. .................................................................................. 58 Figure II-16. Resonance Raman absorption profile for 1-MePh overlaid on the absorption spectrum of 1-MePh. Resonance Raman enhancement data points (red circles) were collected at 407, 458, 488, 514, 568, and 647 nm. ................................................................................. 59 Figure II-17. CASSCF(4,4) S=1 state spin density. ............................................................... 60 Figure III-1 Line bond drawings of D-B-A biradical analogs of oligo(para-phenylene) and oligo(2,5-thiophene) used for distance dependence studies. .................................................. 75 Figure III-2 Thermal ellipsoid plots of 1 (top), 1-pPh (middle left), 1-Ph 2 (bottom left), 2-

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Phonon-assisted relaxation and decoherence of singlet-triplet qubits in Si/SiGe quantum dots

Phonon-assisted relaxation and decoherence of singlet-triplet qubits in Si/SiGe quantum dots

When analyzing electrons in Si, it is important to consider possible effects of the valley degrees of freedom. In particu- lar, the presence of more than one valley can have notable ef- fects when excited states, which differ from the ground state by more than just the spin part, are occupied. For instance, this applies to singlet-triplet qubits in a single QD. When the qubit is in the triplet state, the two electron spins are parallel. Consequently, because of the Pauli exclusion principle, one of the two electrons must occupy an excited state. Compared with the ground state of the QD, the occupied excited state may differ in the valley or in the orbital part. In such sys- tems, it therefore matters whether the orbital level spacing is smaller or greater than the valley splitting [52, 59].

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Synthesis, spectral and cyclic voltammetric studies of iron (III) complexes with N, N’, N” tris (benzimidazolyl) methane ligand

Synthesis, spectral and cyclic voltammetric studies of iron (III) complexes with N, N’, N” tris (benzimidazolyl) methane ligand

ligands in methanol and were characterized by elemental analysis, IR, UV-VIS spectroscopic and other analytical techniques. The cyclic voltammograms of the complexes were taken in DMSO. Cyclic Voltammetric measurement of the complexes display quasi reversible redox wave. The –ve reduction potential values reveal the strong binding of anionic donors stabilizing the Fe (II) oxidation state. The magnetic moment data reveal the monomeric nature. The IR spectral data reveal unidentate mode of binding of the benzimidazole and anionic donors to the iron site. The UV spectra reveal that the UV bands are all blue shifted upon coordination and in general in enhance in intensity. The large molar extinction coefficients reveal that the iron site in the complexes is of low symmetry. The complexes have been screened for their antibacterial and antifungal activity. The result of this study shows that the Fe (III) complexes are effective against the bacterial pathogens.

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Bonding and Magnetism in High Symmetry Nano Sized Graphene Molecules: Linear Acenes C4m+2H2m+4 (m = 2,… 25); Zigzag Hexangulenes C6m**2H6m (m = 2,… 10); Crenelated Hexangulenes C6(3m**2 3m+1)H6(2m 1) (m = 2,… 6); Zigzag Triangulenes Cm**2+4m+1H6m (m = 2,…

Bonding and Magnetism in High Symmetry Nano Sized Graphene Molecules: Linear Acenes C4m+2H2m+4 (m = 2,… 25); Zigzag Hexangulenes C6m**2H6m (m = 2,… 10); Crenelated Hexangulenes C6(3m**2 3m+1)H6(2m 1) (m = 2,… 6); Zigzag Triangulenes Cm**2+4m+1H6m (m = 2,… 15)

were a minimum of 1.5 nm longer than either the long (L) and medium (M) in plane molecular geometry axes including the hydrogen atoms and a c unit cell length equal to 1.5 nm. This is much greater than the graphite interlayer spacing 0.167 nm. In this geometry there were no inter molecular atom-atom distances less than or equal to 1.5 nm. The Brillouin zone integration was restricted to the gamma point. The geometry optimizations were carried out using the conjugate gradient method until the forces acting on each atom were close to or less than 0.05 meV/pm. In this work we calculated geometry, total energy and isometric surfaces of total charge and spin density (where appropriate) for spin states S ¼ 0; 1; 2 (occa- sionally). The calculations for the triangulenes were always performed with unrestricted spin and it was found that the total spin of the ground state invariably converged to 2S ¼ ðm 1Þ unpaired spins. In most cases the starting geometries were constructed using standard CC and CH bond distances for aromatic hydrocarbons. The charge densities were analyzed using the vaspview program and the geometry was visualized using the free software Rasmol. 30)

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Efficient tomography of a quantum many-body system

Efficient tomography of a quantum many-body system

Acknowledgments. Work in Innsbruck was supported by the Austrian Science Fund (FWF) under the grant number P25354-N20, by the European Commission via the integrated project SIQS, by the Institut für Quanteninformation GmbH and by the U.S. Army Research O ffi ce through grant W911NF-14-1-0103. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the o ffi cial views or policies of ARO, the ODNI, or the U.S. Government. We thank H. Shen and T. Brydges for experimental support in the final stage of the experiment. Work in Ulm was supported by an Alexander von Humboldt Professorship, the ERC Synergy grant BioQ, the EU projects QUCHIP and EQUAM, the US-Army Research O ffi ce Grant No. W91-1NF-14-1-0133 and the BMBF Verbundproject QuOReP. Numerical computations have been supported by the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant no INST 40 / 467-1 FUGG. I.D. acknowledges support from the Alexander von Humboldt Foundation. M.H. acknowledges contributions from Daniel Suess to jointly developed code used for data analysis. Work at Strathclyde is supported by the European Union Horizon 2020 collaborative project QuProCS (grant agreement 641277), and by AFOSR grant FA9550-12- 1-0057. M.C. acknowledges: the ERC grant QFTCMPS and SIQS, the cluster of excellence EXC201 Quantum Engineering and Space-Time Research, and the DFG SFB 1227 (DQ-mat). T. B. acknowledges: EPSRC (EP / K04057X / 2) and the UK National Quantum Technologies Programme (EP / M01326X / 1). B. P. L. acknowledges support by the START prize of the Austrian FWF project Y 849-N20.

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Estimating the Frequency of Events That Cause Multiple-Nucleotide Changes

Estimating the Frequency of Events That Cause Multiple-Nucleotide Changes

presence of mutational hot spots. However, the levels of The exact cause of these high estimates, however, doublet and triplet mutation events estimated from the remains open to debate. It seems unlikely that misspeci- data are very high and occur over a wide variety of fication of the model caused, for example, by high levels biological sequences. Given the plausible biological ex- of variation in selection along proteins or poor data quality planation of such events, it seems unlikely that misspeci- can be the sole cause of the high estimates of doublet fications of the model, such as those discussed above, and triplet mutation. The lack of a biological mechanism are the sole cause of the high estimates of doublet and for triplet mutation, the more prevalent of the two types

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Remotely induced magnetism in a normal metal using a superconducting spin valve

Remotely induced magnetism in a normal metal using a superconducting spin valve

thicknesses in nm and x = 5 or 70. They consist of an S/F interface with an additional N layer atop the S, as well as a second F layer separated from the first by a thin normal metal spacer (n) creating a NSFnF device, shown schematically in Fig.1 (see supplementary information for more details of our spin valves). In our devices the exchange field of the outer F layer (Co(1.2)), can be pinned magnetically, by using an anti-ferromagnet (IrMn), while retaining easy manipulation of the other F layer (Co(2.4)). This enables us to control the angle between the two F

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Excited state reactions of some aromatic carbonyl compounds

Excited state reactions of some aromatic carbonyl compounds

All the above cases of carbonyl protonation, except for 4-phenylbenzophenone, show the pK order pK(T^) > pK(8 ^) > pK(S^), but as shown in Chapter 4 the precise order depends very much on the particular case involved. For example, in the case of 5-nitro-2- hydroxybenzophenone, we find the calculations indicate an increase in basic strength in the first singlet state but that the first triplet state, nevertheless, becomes a weaker base giving the order pK(S^) > pK(S^) > pK(T^), No general system of inequalities can be given for the three pK values; the case of each compound must be separately considered.

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Final State Interactions and Polarization Observables in the Reaction pp → pKΛ

Final State Interactions and Polarization Observables in the Reaction pp → pKΛ

the event sample into four subsamples: One for beam spin up and the quantization axis of the Λ in the same detector hemisphere (↑↑) and another for the opposite detector hemisphere (↑↓). Additional sam- ples with beam spin down (↓↓,↓↑) are important to control systematic e ff ects from azimuthal angular asymmetries in the detector acceptance. The corresponding polarizations are shown in Fig. 3 on the left. The depolarization on the right is then simply determined by the di ff erences of the Λ polarization of the four subsamples [2].

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Photochemistry of Styrene Oxide: A Triplet Pathway in the Singlet Excitation of a Monoaryl Oxirane

Photochemistry of Styrene Oxide: A Triplet Pathway in the Singlet Excitation of a Monoaryl Oxirane

of 1 (0.05M) in the presence of a triplet quencher isoprene (0.015 M) exhibited a 69% reduction in the early formation of both 3 and 6 in the early stages of the photoreaction, which shows a triplet pathway for the formation 3 and 6 as pri- mary photoproducts. Quenching of the triplet most likely occurs prior to the dissociation of the benzylic C-C bond as indicated by the reduction of 3 and the absence of any carbonyl ylid derived products.

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Ab Initio Calculations of SiO2 and ZnO Defect Structures.

Ab Initio Calculations of SiO2 and ZnO Defect Structures.

The answer is given by the ground state analysis, where the energy difference between the lowest singlet and triplet states is broken down into different contributing factors. We conclude that when the two Si atoms next to the O vacancy are far apart, interpreted here as a distance larger than 4.9Å, it is likely that both states are be occupied. This distance is much larger than the normal Si-Si distance in a Si-O-Si bonding (< 3Å). This implies that if the structure is created out of strained Si-O-Si bonding, significant local structural relaxation is involved.

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Calorimetric observation of single He2* excimers in a 100 mK He bath

Calorimetric observation of single He2* excimers in a 100 mK He bath

Fig. 5 a The triplet state excimer is to the right of the dashed line (one He atom in the ground state and one in an excited state) and the TES is to the left of the dashed line. The horizontal axis is distance, and the vertical axis is energy. E v is the vacuum energy and E F is the Fermi energy of the TES. E g is the ground-state energy of the excimer. The gradient region depicts an arbitrary non-uniform density of states below the Fermi level in the TES. E 1 − E g is the excimer energy and is about 15 eV. E 1 is roughly 4 eV below E v , but shifts upwards as the excimer approaches the TES surface. b The processes involved in the excimer quenching on the detector (blue arrows) is numbered in order of occurrence 1: the excited electron tunnels into a free state in the TES and relaxes to the Fermi surface. 2: An electron from the TES Fermi sea fills the empty ground state of the helium molecule, and the molecule splits into two atoms. 3: An Auger electron is promoted from within the TES Fermi sea and has energy E 3 − E g . Finally, electrons relax from the Fermi surface to fill the two empty states in the TES (this is not pictured). Energies E 2 and E 3 are arbitrary as these two electrons may source from anywhere in the TES Fermi sea (Color figure online)

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Bethe-Salpeter wave functions of ηc(1S, 2S) and ψ(1S, 2S) states: local-potential description of the charmonium system revisited

Bethe-Salpeter wave functions of ηc(1S, 2S) and ψ(1S, 2S) states: local-potential description of the charmonium system revisited

m Q (1S ) = 1.847(145) GeV from the 2S wave functions by a constant fit over above r range with χ 2 /d.o.f. < 2. These values are consistent with each other, and also with our previous work as listed in Table 2. It indicates that within the current precision a unique result for the quark kinetic mass is likely given regardless of the choice of either the ground- or excited-state pairs. This observation is highly consistent with success of potential description of the charmonium system.

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Photodynamic Therapy in Periodontics: A Review

Photodynamic Therapy in Periodontics: A Review

PDT is based on the principle that a photoactivable substance (photosensitiser) binds to the target cell can be activated by light of suitable wavelength. During this process, free radicals are formed (among them singlet oxygen) which then produce an effect that is toxic to the cells. For bactericidal effect on the cells, the respective photosensitiser needs to have selectivity for prokaryotic cells. Some authors have reported the possibility of lethal photosensitisation of bacteria in vivo and in vitro (Martinetto et al. 1986; Wilson 1993; De Simone 1999; Bertoloni et al. 1992).

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The mechanical and thermal properties of the nitrogen vacancy centre in diamond

The mechanical and thermal properties of the nitrogen vacancy centre in diamond

A challenging consequence of utilising quantum objects for computers or sensors is that often their quantum state is fragile or hard to read and control. Because of this fragility, many systems rely on isolation from their environment by using ultra-high vacuums (e.g. magnetic resonance force microscopy [1], scanning tun- nelling microscopy [2]), cryogenic temperatures (e.g. SQUIDS [3], quantum dots [4], phosphorus in silicon [5], superconducting circuits [6]) or other sophisticated isolation devices (e.g. ion traps [7], magneto-optical traps [8]). This is particularly problematic for quantum sensors, as non-ambient conditions exclude many systems of critical interest in chemical and biomedical research, such as live specimens or highly temperature dependent proteins and molecules. A quantum system that is robust enough to be useful in ambient conditions is going to be a more capable sensor to study these important systems. Similarly, a quantum system that is small (atom-like) will have a natural ability to measure and image processes at length scales much smaller than larger and more isolated devices.

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