A molecular model for positron complexes: long-range effects on 2 pair-annihilation rates

The adiabatic approximation to positronic atoms and molecules was considered as an option to the computationally unfeasible methods that treat all particles in a common footing, in two different approaches communicated in the 37th PSPA. Here we present further assessment and comparison of the two approaches as a way of evaluating the potential of adiabatic or, as we found preferable, molecular approaches.

Section: Modelsmentioning

confidence: 99%

Is a Molecular Adiabatic Approximation Appropriate to Positronic Atoms and Molecules?

Mohallem

2008

“…[1], we proposed that the pair annihilation rate of Ps, Γ = 2.0 × 10 9 s −1 , is a lower bound to the annihilation rate per positron in any complex in a state that breaks in one or more Ps atoms. Thus for Ps 2 O we predict Γ > ∼ 4.0 × 10 9 s −1 which is in consonance with the calculation of Ref.…”

Section: The Molecular Structure Of [Ps 2 O] and [Psoh]mentioning

confidence: 99%

“…As a consequence, these calculations are computationally quite hard and limited to very small systems. We have found, on the other hand, that treating a positron as a light nucleus and performing an adiabatic separation of the electronic and nuclear motions, a lot of valuable information can be obtained from the potential energy surface (PES) for nuclei and positron motions [1,2]. Despite the need of a large adiabatic correction to positron motion, everything else works as in standard molecular structure calculations.…”

Section: Introduction: the Molecular Model For Positron Complexesmentioning

confidence: 99%

“…For example, for a general complex [e + ;A] the point of minimum energy of the PES gives the geometry of the parent A system but just an approximation to the average position of the positron. Even though, predictions of positron bonding sites and geometry relaxation [2] and estimative of annihilation rates [1] are available within the molecular model.…”

Section: Introduction: the Molecular Model For Positron Complexesmentioning

confidence: 99%

See 1 more Smart Citation

Molecular Structure of Water-Like Positronium Complexes

Rolim¹,

Mohallem

2005

“…Fully different philosophy of treating the positron as a light pseudonucleus was used in the works of Stachowiak and Boroński [26] and Mohallem et al [27][28][29][30]. The idea of separation of the positronic motion from the electronic one appeared even earlier -the nonexistence of some bound positronic atoms has been shown within such approach [31].…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Positronic Atoms with Adiabatic Separation of Positronic Motion

Strasburger

Wołcyrz

2008

A modified adiabatic approximation, with the positron treated as a light nucleus and its charge included only partially in the electronic Hamiltonian, was applied to compute the energies and properties of bound states of lithium positride, positronic beryllium and positronic magnesium. The electronic Schrödinger equation was solved with the configuration interaction method. No bound state was obtained for lithium positride, while the dissociation energies of positronic beryllium and positronic magnesium were underestimated by 2.6 and 7 millihartrees, respectively. Consequences for the applicability of the adiabatic approximation to describe positronic systems are discussed.