Physical constraints on nonstationary states and nonexponential decay

Nicolaides, CA

dc.contributor.author	Nicolaides, CA	en
dc.date.accessioned	2014-03-01T01:52:08Z
dc.date.available	2014-03-01T01:52:08Z
dc.date.issued	2002	en
dc.identifier.issn	1050-2947	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/26578
dc.subject.classification	Optics	en
dc.subject.classification	Physics, Atomic, Molecular & Chemical	en
dc.subject.other	TIME-DEPENDENCE	en
dc.subject.other	AUTOIONIZING STATES	en
dc.subject.other	EXPONENTIAL DECAY	en
dc.subject.other	QUANTUM ZENO	en
dc.subject.other	RESONANCES	en
dc.subject.other	PROBABILITY	en
dc.subject.other	THRESHOLD	en
dc.subject.other	ENERGIES	en
dc.subject.other	HE-2(2+)	en
dc.subject.other	BEHAVIOR	en
dc.title	Physical constraints on nonstationary states and nonexponential decay	en
heal.type	journalArticle	en
heal.identifier.secondary	022118	en
heal.language	English	en
heal.publicationDate	2002	en
heal.abstract	For the understanding of irreversibility at the quantum level, the formation and decay of transient (unstable) states play a fundamental role. If the system is treated within Hermitian quantum mechanics, the resulting energy distribution of the resonance state, whose Fourier transform yields the time-dependent probability of decay, P(t), is real. The physical constraint of the lower bound in the energy spectrum introduces "memory," and causes nonexponential decay (NED) to set in after t>tau, where tau is the lifetime defined by exponential decay. The closer to threshold the decaying state is, the earlier NED appears. Apart from the constraint of Egreater than or equal to0, the constraint of tgreater than or equal to0 must be accounted for at the same time. It results from the discontinuity at t=0 of the solution of the time-dependent Schrodinger equation, which breaks the unitarity associated with the S matrix and gives rise to a complex energy distribution, as a manifestation of the non-Hermitian property of the decaying states. For a narrow isolated resonance state, for which the self-energy is essentially energy-independent, analytic results for P-NED(t) obtained from semiclassical path-integral calculations agree with the quantum-mechanical ones when both physical constraints E>0 and t>0 are taken into account. As an example of the difference in the magnitude of the P-NED(t) when using a real and a complex energy distribution, application is made to the decay of the unstable He-2(2+) (1)Sigma(g)(+) ground molecular state.	en
heal.publisher	AMERICAN PHYSICAL SOC	en
heal.journalName	PHYSICAL REVIEW A	en
dc.identifier.isi	ISI:000177872600026	en
dc.identifier.volume	66	en
dc.identifier.issue	2	en