On the violation of the exponential decay law in atomic physics: Ab initio calculation of the time-dependence of the He- 1s2p(2) P-4 non-stationary state

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dc.contributor.author Nicolaides, CA en
dc.contributor.author Mercouris, T en
dc.date.accessioned 2014-03-01T01:45:13Z
dc.date.available 2014-03-01T01:45:13Z
dc.date.issued 1996 en
dc.identifier.issn 0953-4075 en
dc.identifier.uri http://hdl.handle.net/123456789/24565
dc.subject.classification Optics en
dc.subject.classification Physics, Atomic, Molecular & Chemical en
dc.subject.other SPONTANEOUS EMISSION en
dc.subject.other AUTOIONIZING STATES en
dc.subject.other BOUND-STATES en
dc.subject.other LONG TIMES en
dc.subject.other PHOTODETACHMENT en
dc.subject.other DEVIATIONS en
dc.subject.other THRESHOLD en
dc.subject.other RESONANCES en
dc.subject.other SYSTEMS en
dc.title On the violation of the exponential decay law in atomic physics: Ab initio calculation of the time-dependence of the He- 1s2p(2) P-4 non-stationary state en
heal.type journalArticle en
heal.language English en
heal.publicationDate 1996 en
heal.abstract The detailed time dependence of the decay of a three-electron autoionizing state close to threshold has been obtained ab initio by solving the time-dependent Schrodinger equation (TDSE). The theory allows the definition and computation of energy-dependent matrix elements in terms of the appropriate N-electron wavefunctions, representing the localized initial state, psi(0) the stationary scattering states of the continuous spectrum, U(epsilon), and the localized excited states, psi(n), of the effective Hamiltonian QHQ, where Q = \psi(0)><psi(0)\. The time-dependent wavefunction is expanded over these states and the resulting coupled equations with time-dependent coefficients (in the thousands) are solved to all orders by a Taylor series expansion technique. Convergence is checked as a function of the number of the numerically obtained U(epsilon) that span the continuous spectrum of the free electron. The robustness of the method was verified by using a model interaction in analytic form and comparing the results from two different methods for integrating the TDSE (appendix B). For the physically relevant application, the chosen state was the He- 1s2p(2) P-4 shape resonance, about which very accurate theoretical and experimental relevant information exists. Calculations using accurate wavefunctions and an energy grid of 20.000 points in the range 0.0-21.77 eV show that the effective interaction depends on energy in a state-specific manner, thereby leading to state-specific characteristics of non-exponential decay (NED). For the established energy position of 0.01 eV, the results show an exponential decay over about 6 x 10(4) au of time, from which a width of Gamma = 5.2 meV and a lifetime of 1.26 x 10(-13) s is deduced. The experimentally obtained width is 7.16 meV (Walter, Seifert and Peterson 1994 Phys. Rev. A 50 664). After 12 lifetimes (about 1400 fs), at which time the survival probability is 10(-6), NED sets in. On the other hand, due to the shape of the interaction, the NED appears at earlier times if the energy position happened to be slightly larger. For example, if E were at 0.019 eV, NED would Start after nine exponential lifetimes. These facts suggest that either in this state or in other autoionizing states close to threshold, NED may have sufficient presence to make the violation of the law of exponential decay observable. en
heal.publisher IOP PUBLISHING LTD en
dc.identifier.isi ISI:A1996UD88000012 en
dc.identifier.volume 29 en
dc.identifier.issue 6 en
dc.identifier.spage 1151 en
dc.identifier.epage 1167 en

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