Rosen–Zener model in cold molecule formation

The beam scattering method was used to investigate non-dissociative single-electron charge transfer between the molecular dication CO22+ and Ar or Ne at several collision energies between 3-10 eV (centre-of-mass, c.m.). Relative translational energy distributions of the product ions showed that in the reaction with Ar the CO2+ product was mainly formed in reactions of the ground state of the dication, CO22+(X3Σg-), leading to the excited states of the product CO2+(A2Πu) and CO2+(B2Σu+). In the reaction with Ne, the largest probability had the process from the reactant dication excited state CO22+(1Σg+) leading to the product ion ground state CO2+(X2Πg). Less probable were processes between the other excited states of the dication CO22+, (1∆g), (1Σu-), (3∆u), also leading to the product ion ground state CO2+(X2Πg). Using the Landau-Zener model of the reaction window, relative populations of the ground and excited states of the dication CO22+ in the reactant beam were roughly estimated as (X3Σg):(1∆g):(1Σg+):(1Σu-):(3∆u) = 1.0:0.6:0.5:0.25:0.25.

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Nearly perfectly matched layer absorber for viscoelastic wave equations

Geophysics ◽

10.1190/geo2018-0732.1 ◽

2019 ◽

Vol 84 (5) ◽

pp. T335-T345

Author(s):

Enjiang Wang ◽

José M. Carcione ◽

Jing Ba ◽

Mamdoh Alajmi ◽

Ayman N. Qadrouh

Keyword(s):

Wave Equations ◽

Pseudospectral Method ◽

Perfectly Matched Layer ◽

Zener Model ◽

Fourier Pseudospectral Method ◽

Time Stepping ◽

First Case ◽

Stress Strain Relation ◽

Viscoelastic Wave ◽

Spatial Derivatives

We have applied the nearly perfectly matched layer (N-PML) absorber to the viscoelastic wave equation based on the Kelvin-Voigt and Zener constitutive equations. In the first case, the stress-strain relation has the advantage of not requiring additional physical field (memory) variables, whereas the Zener model is more adapted to describe the behavior of rocks subject to wave propagation in the whole frequency range. In both cases, eight N-PML artificial memory variables are required in the absorbing strips. The modeling simulates 2D waves by using two different approaches to compute the spatial derivatives, generating different artifacts from the boundaries, namely, 16th-order finite differences, where reflections from the boundaries are expected, and the staggered Fourier pseudospectral method, where wraparound occurs. The time stepping in both cases is a staggered second-order finite-difference scheme. Numerical experiments demonstrate that the N-PML has a similar performance as in the lossless case. Comparisons with other approaches (S-PML and C-PML) are carried out for several models, which indicate the advantages and drawbacks of the N-PML absorber in the anelastic case.

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