Search results for "quantum [effect]"
showing 10 items of 5105 documents
Gravity Probe Spin: Prospects for measuring general-relativistic precession of intrinsic spin using a ferromagnetic gyroscope
2020
An experimental test at the intersection of quantum physics and general relativity is proposed: measurement of relativistic frame dragging and geodetic precession using intrinsic spin of electrons. The behavior of intrinsic spin in spacetime dragged and warped by a massive rotating body is an experimentally open question, hence the results of such a measurement could have important theoretical consequences. Such a measurement is possible by using mm-scale ferromagnetic gyroscopes in orbit around the Earth. Under conditions where the rotational angular momentum of a ferromagnet is sufficiently small, a ferromagnet's angular momentum is dominated by atomic electron spins and is predicted to e…
No-core configuration-interaction model for the isospin- and angular-momentum-projected states
2016
[Background] Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multi-reference level allows for restoring symmetries and, in turn, for calculating transition rates. [Purpose] We propose a new no-core-configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus. [Metho…
The à 1Au state and the T2 potential surface of acetylene: Implications for triplet perturbations in the fluorescence spectra of the à state
1996
The cis–trans isomerization reaction on the T2 surface of acetylene and the lowest excited singlet state of acetylene, A 1Au, are investigated by ab initio electronic structure theory. We report optimized geometries, dipole moments, and harmonic vibrational frequencies of stationary points and adiabatic energy differences between them using basis sets as large as triple‐ζ plus double polarization with higher angular momentum functions, TZ(2df,2pd), and theoretical methods up to coupled‐cluster singles and doubles with a perturbative triples correction [CCSD(T)] and the equation‐of‐motion coupled‐cluster method (EOM‐CCSD). Our theoretical predictions should aid the interpretation of observat…
Counterdiabatic vortex pump in spinor Bose-Einstein condensates
2017
Topological phase imprinting is a well-established technique for deterministic vortex creation in spinor Bose-Einstein condensates of alkali metal atoms. It was recently shown that counter-diabatic quantum control may accelerate vortex creation in comparison to the standard adiabatic protocol and suppress the atom loss due to nonadiabatic transitions. Here we apply this technique, assisted by an optical plug, for vortex pumping to theoretically show that sequential phase imprinting up to 20 cycles generates a vortex with a very large winding number. Our method significantly increases the fidelity of the pump for rapid pumping compared to the case without the counter-diabatic control, leadin…
Scope and Limitations of Baird's Theory on Triplet State Aromaticity: Application to the Tuning of Singlet–Triplet Energy Gaps in Fulvenes
2007
Utilizing Baird's theory on triplet state aromaticity, we show that the singlet-triplet energy gaps (DeltaE(ST)) of pentafulvenes are easily varied through substitution by as much as 36 kcal mol(-1). This exploits the fact that fulvenes act as aromatic chameleons in which the dipoles reverse on going from the singlet ground state (S(0)) to the lowest pipi* triplet state (T1); thus, their electron distributions are adapted so as to achieve some aromaticity in both states. The results are based on quantum chemical calculations with the OLYP density functional theory method and the CASPT2 ab initio method, as well as spectroscopic determination of DeltaE(ST) by triplet sensitization. The findi…
Ring splitting of azetidin-2-ones via radical anions
2012
The radical anions of azetidin-2-ones, generated by UV-irradiation in the presence of triethylamine, undergo ring-splitting via N-C4 or C3-C4 bond breaking, leading to open-chain amides. This reactivity diverges from that found for the neutral excited states, which is characterised by alpha-cleavage. The preference for beta-cleavage is supported by DFT theoretical calculations on the energy barriers associated with the involved transition states. Thus, injection of one electron into the azetidin-2-one moiety constitutes a complementary activation strategy which may be exploited to produce new chemistry.
NMR Spectroscopic Evidence for the Intermediacy of XeF3− in XeF2/F− Exchange, Attempted Syntheses and Thermochemistry of XeF3− Salts, and Theoretical…
2010
The existence of the trifluoroxenate(II) anion, XeF(3)(-), had been postulated in a prior NMR study of the exchange between fluoride ion and XeF(2) in CH(3)CN solution. The enthalpy of activation for this exchange, ΔH(⧧), has now been determined by use of single selective inversion (19)F NMR spectroscopy to be 74.1 ± 5.0 kJ mol(-1) (0.18 M) and 56.9 ± 6.7 kJ mol(-1) (0.36 M) for equimolar amounts of [N(CH(3))(4)][F] and XeF(2) in CH(3)CN solvent. Although the XeF(3)(-) anion has been observed in the gas phase, attempts to prepare the Cs(+) and N(CH(3))(4)(+) salts of XeF(3)(-) have been unsuccessful, and are attributed to the low fluoride ion affinity of XeF(2) and fluoride ion solvation in…
"Identification of mixed bromidochloridotellurate anions in disordered crystal structures of (bdmim)2[TeX2Y4] (X, Y = Br, Cl; bdmim = 1-butyl-2,3-dim…
2013
Abstract The discrete mixed [TeBrxCl6−x]2− anions in their disordered crystal structures have been identified by using the phases prepared by the reaction of 1-butyl-2,3-dimethylimidazolium halogenides (bdmim)X with tellurium tetrahalogenides TeX4 (X = Cl, Br) as examples. Homoleptic (bdmim)2[TeX6] [X = Cl (1), Br (2)] and mixed (bdmim)2[TeBr2Cl4] (3), and (bdmim)2[TeBr4Cl2] (4) are formed depending on the choice of the reagents, and their crystal structures have been determined by single-crystal X-ray diffraction. The coordination environments of tellurium in all hexahalogenidotellurates are almost octahedral. Because of the crystallographic disorder, the mixed [TeBr2Cl4]2− and [TeBr4Cl2]2…
Island Homoaromaticity in the W-Shaped 2,4-Diphospha-3-arsapentadienide Anion and Related Compounds - Theoretical and Experimental Investigations
2012
A series of anions with general formula (R2C=P)2Pn– (Pn = N, P, As, Sb; R = H, Me, CF3, SiH3, SiMe3, SiF3) was investigated theoretically at the DFT (RI-BP86/TZVP) and RI-MP2/TZVP levels of approximation. Significantly sharpened central PPnP bond angles were predicted for the species with π-acceptor R substituents. The corresponding bond angle values decrease in the order Pn = N >> P > As > Sb. This finding is in agreement with the previously published structural data for [(Me3Si)2C=P]2P–. An island homoaromaticity was proposed as a suitable explanation for the observed effect. In more detail, it consists of shifting negative charge to the electron-withdrawing terminal groups with formation…
Synthesis, reactivity, and computational analysis of halophosphines supported by dianionic guanidinate ligands.
2012
The reported chemistry and reactivity of guanidinate supported group 15 elements in the +3 oxidation state, particularly phosphorus, is limited when compared to their ubiquity in supporting metallic elements across the periodic table. We have synthesized a series of chlorophosphines utilizing homo- and heteroleptic (dianionic)guanidinates and have completed a comprehensive study of their reactivity. Most notable is the reluctancy of these four-membered rings to form the corresponding N-heterocyclic phosphenium cations, the tendency to chemically and thermally eliminate carbodiimide, and the scarcely observed ring expansion by insertion of a chloro(imino)phosphine into a P-N bond of the P-N-…