Quasistationary Stabilization of the Decay of a Weakly-Bound Level and Its Breakdown in a Strong Laser Field

Although it was pointed out about 10 years ago that an atomic decay rate might decrease as the intensity of a high-frequency laser field increases, there still does not exist any complete understanding of either the physical origin of this interesting nonlinear phenomenon or its dependence on the atomic and field parameters. Essentially, the problem consists in that the phenomenon requires a major modification of the standard picture of photoeffect in a strong laser field. In Reference #1 the origin of this stabilization is related to a particular distortion of an atomic potential by an intense monochromatic high-frequency field. This phenomenon is called adiabatic or quasistationary stabilization (QS). For the case of Rydberg levels, another (interference) mechanism of QS was suggested. Both theories predict an unlimited decrease of the decay rate (or of the width Γ of an atomic level, i.e., of the imaginary part of the complex quasienergy, ε = Re ε – iΓ/2 ) as the laser field amplitude increases. In recent years the idea of “dynamic stabilization” (DS) has become popular. It originates from the pulse form of a laser field rather than from any intrinsic property of the atom in a strong monochromatic field. Within this model the numerous simulations point also to the possibility of a breakdown of stabilization for the case of superintense short laser pulses. However, a recent paper, using the quasistationary quasienergy states (QQES) as an adiabatic basis for the laser pulse has shown that DS has the same (quasistationary) origin as QS. Finally, a number of authors deny the existence of stabilization, in particular, of QS for ionization from a short-range potential and of DS in pulsed fields. Obviously, these controversies and ambiguities are caused by the complexity of the numerical solution of the Cauchy problem for the time-dependent Schrödinger equation in a strong field and by the absence of analyses for exactly solvable analytical models. We analyze the exactly solvable problem of an electron in a three-dimensional, short-range potential and consider the two questions: does a QS-like behavior of the decay rate exist for this model, and, if so, is there an upper intensity limit of the QS regime

Control of harmonic generation by the time delay between two-color, bicircular few-cycle mid-IR laser pulses

We study control of high-order harmonic generation (HHG) driven by time-delayed, few-cycle ω and 2ω counterrotating mid-IR pulses. Our numerical and analytical study shows that the time delay between the two-color pulses allows control of the harmonic positions, both those allowed by angular momentum conservation and those seemingly forbidden by it. Moreover, the helicity of any particular harmonic is tunable from left to right circular without changing the driving pulse helicity. The highest HHG yield occurs for a time delay comparable to the fundamental period T=2π/ω

Young Australian consumers and the country-of-origin effect: investigation of the moderating roles of product involvement and perceived product-origin congruency

The effect that consumers’ country-related images have on their purchase decisions is known as the country-of-origin effect. Marketing researchers have thoroughly investigated COO effects in a range of contexts since the mid-1960s. However, since the 1980s it has been thought (e.g., Levitt, 1983; Ohmae, 1995) that consumer needs and wants are converging and that nation states are artificial and superficial entities of little value as quality indicators. The argument is that since the world is changing and because young consumers are used to seeing products from a variety of countries they do not have the country biases that the COO effect stipulates. Indeed, a recent study (Wong et al., 2008) on young Chinese consumers and the COO effect seems to confirm that young consumers no longer are influenced by the COO effect. The aim of this research is to investigate if and how the relationship between young Australian consumers’ product-country image and their product evaluations is influenced by two contextual variables: their product involvement and their perceived product-origin congruency. The research reports the results and relevant implications for research and practice