The multiphoton ionization rate and the energy shift of atoms interacting with weak dichromatic fields with commensurate frequencies are simple functions of the phase difference

Mercouris, T; Nicolaides, CA

dc.contributor.author	Mercouris, T	en
dc.contributor.author	Nicolaides, CA	en
dc.date.accessioned	2014-03-01T01:17:15Z
dc.date.available	2014-03-01T01:17:15Z
dc.date.issued	2001	en
dc.identifier.issn	1434-6060	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/14418
dc.subject.classification	Physics, Atomic, Molecular & Chemical	en
dc.subject.other	ABOVE-THRESHOLD IONIZATION	en
dc.subject.other	INTENSE LASER FIELD	en
dc.subject.other	MANY-PHOTON THEORY	en
dc.subject.other	UNIMOLECULAR REACTIONS	en
dc.subject.other	ANGULAR-DISTRIBUTIONS	en
dc.subject.other	NEGATIVE-IONS	en
dc.subject.other	2-COLOR	en
dc.subject.other	PHOTOIONIZATION	en
dc.subject.other	ELECTRON	en
dc.subject.other	INTERFERENCE	en
dc.title	The multiphoton ionization rate and the energy shift of atoms interacting with weak dichromatic fields with commensurate frequencies are simple functions of the phase difference	en
heal.type	journalArticle	en
heal.identifier.primary	10.1007/s100530170222	en
heal.identifier.secondary	http://dx.doi.org/10.1007/s100530170222	en
heal.language	English	en
heal.publicationDate	2001	en
heal.abstract	By implementing a time-independent, nonperturbative many-electron, many-photon theory (MEMPT), cycle-averaged complex eigenvalues were obtained for the He atom, whose real part gives the field-induced energy shift, Δ(w1, F1; w2, F2, Mathematical bold italic small phi sign), and the imaginary part is the multiphoton ionization rate, Γ(w1, F1; w2, F2, Mathematical bold italic small phi sign), where w is the frequency, F is the field strength and Mathematical bold italic small phi sign is the phase difference. Through analysis and computation we show that, provided the intensities are weak, the dependence of Γ(w1, F1; w2, F2, Mathematical bold italic small phi sign) on Mathematical bold italic small phi sign is simple. Specifically, for odd harmonics, Γ varies linearly with cos(Mathematical bold italic small phi sign) whilst for even harmonics it varies linearly with cos(2Mathematical bold italic small phi sign). In addition, this dependence on Mathematical bold italic small phi sign holds for Δ(w1, F1; w2, F2, Mathematical bold italic small phi sign) as well. These relations may turn out to be applicable to other atomic systems as well, and to provide a definition of the weak field regime in the dichromatic case. When the combination of (w1, F1) and (w3, F2) is such that higher powers of cos(Mathematical bold italic small phi sign) and cos(2Mathematical bold italic small phi sign) become important, these rules break down and we reach the strong field regime. The herein reported results refer to Γ(w1, F1; w2, F2, Mathematical bold italic small phi sign) and Δ(w1, F1; w2, F2, Mathematical bold italic small phi sign) for He irradiated by a dichromatic ac-field consisting of the fundamental wavelength λ = 248 nm and its 2nd, 3rd and 4th higher harmonics. The intensities are in the range 1.0 × 1012-3.5 × 1014 W/cm2, with the intensity of the harmonics being 1-2 orders of magnitude smaller. The calculations incorporated systematically electronic structure and electron correlation effects in the discrete and in the continuous spectrum, for1S,1P,1D,1F,1G, and1H two-electron states of even and odd parity.	en
heal.publisher	SPRINGER-VERLAG	en
heal.journalName	European Physical Journal D	en
dc.identifier.doi	10.1007/s100530170222	en
dc.identifier.isi	ISI:000168944000013	en
dc.identifier.volume	14	en
dc.identifier.issue	2	en
dc.identifier.spage	241	en
dc.identifier.epage	248	en