Photochemical Reaction Mechanism of Intramolecular H Transfer Reaction of H2C3O+⋅ Radical Cation

The photochemical reaction mechanism underlying the intramolecular H-transfer of the H₂C₃O⁺⋅ radical cation to the H₂CCCO⁺⋅ methylene ketene cation was elucidated using time-dependent density functional theory and high-level ab initio methods. Once the D₁ state of H₂C₃O⁺⋅ is populated, the reaction proceeds to form an intermediate (IM) in the D₁ state (IM4_D1). The molecular structure of the conical intersection (CI) was optimized using a multiconfigurational ab initio method. The CI is readily accessible because it lies slightly above the IM4_D1 in energy. In addition, the gradient difference vector of the CI is almost parallel to the intramolecular H-transfer reaction coordinate. Once the vibration mode of IM4_D1 which is parallel to the reaction coordinate is populated, the degeneracy of the CI is readily lifted and H₂CCCO⁺⋅ was formed via a relaxation pathway in the D₀ state. Our calculated results clearly describe the photochemical intramolecular H transfer reaction reported in a recent study.     

Asymptotic Stability of Harmonic Maps on the Hyperbolic Plane under the Schrödinger Maps Evolution

We consider the Cauchy problem for the Schrödinger maps evolution when the domain is the hyperbolic plane. An interesting feature of this problem compared to the more widely studied case on the Euclidean plane is the existence of a rich new family of finite energy harmonic maps. These are stationary solutions, and thus play an important role in the dynamics of Schrödinger maps. The main result of this article is the asymptotic stability of (some of) such harmonic maps under the Schrödinger maps evolution. More precisely, we prove the nonlinear asymptotic stability of a finite energy equivariant harmonic map under the Schrödinger maps evolution with respect to non-equivariant perturbations, provided obeys a suitable linearized stability condition. This condition is known to hold for all equivariant harmonic maps with values in the hyperbolic plane and for a subset of those maps taking values in the sphere. One of the main technical ingredients in the paper is a global-in-time local smoothing and Strichartz estimate for the operator obtained by linearization around a harmonic map, proved in the companion paper [36]. © 2021 Wiley Periodicals LLC.     

Radio frequency field intensity mapping using a composite spin-echo sequence

A novel radio frequency (RF) field intensity mapping or imaging method using a composite NMR spin-echo sequence is proposed. A composite spin-echo RF pulse with 90 degrees y-180 degrees x-90 degrees y sequence makes phase change in the final image depending on the RF field intensity on the object. The resultant phase change or phase map can be used to obtain the actual RF flip-angle map for a given condition which includes the status of tuning and RF inhomogeneity, etc. Bloch equation has been solved numerically to obtain the effects of the RF field intensity as well as the main magnetic field inhomogeneity and the results are used for the mapping (imaging) of the RF field intensity. Phantom studies have been performed using a 1.5 Tesla whole body MRI system and the results are presented.     

Photoemission studies of clean and oxidized Cs

Photoemission studies of the oxidation of Cs at ～ 140 K have been carried out. Four different states of oxygen were observed. Definitive identification of three of the four states has been achieved in two steps: (1) comparison of the multiplet structure of free oxygen ions and the multiplet structure in the photoemission spectra of oxygen sorbed in Cs (i.e., comparison of the energy separations of the various oxygen levels involved); and (2) comparison of experimentally measured binding energies of various states of oxygen with calculated binding energies of known oxygen species inserted in Cs. The oxygen species identified are O^2?, O₂^2? and O₂^?. The multiplet structure of O₂^2? in Cs is identical to that expected for free O₂^2? with no differential relaxation of orbital energies. In contrast, significant differential relaxation in orbital energies is observed for O₂^? in Cs. This difference is attributed to the closed-shell and open-shell configurations of O₂^2? and O₂^?, respectively. The oxidation-induced changes in the Cs 4d, 5s and 5p core levels and the NOO and OVV Auger transitions have also been studied in detail. A discussion of the oxidation of Cs, based on the oxygen species identified definitively, is also given.     

Nonlinear supersymmetric standard model and its phenomenology

We consider the Higgs sector of a nonlinear supersymmetric standard model. Analytic solutions for some useful mass relations are derived. We investigate physical consequences of the model for LEP 1, LEP 2, and 500, 1000 resp. 2000 GeV LCs, and show that the neutral scalar Higgs bosons will most probably enable LC 500, 1000, 2000 to test the model conclusively, whereas at LEP 1, 2 only a part of the parameter space can be explored. As for the two pseudoscalar Higgs bosons the lighter one cannot be detected at any of the considered colliders, whereas the heavier one could possibly be detected with about “10 percent probability” at LC 1000 and LC 2000.