Two-electron processes in multiple ionization under strong soft-x-ray radiation

In a combined experimental and theoretical study we have investigated the ionization of atomic argon upon irradiation with intense soft-x-ray pulses of 105 eV photon energy from the free-electron laser FLASH. The measured ion yields show charge states up to Ar7+. The comparison with the theoretical study of the underlying photoionization dynamics highlights the importance of excited states in general and of processes governed by electron correlation in particular, namely, ionization with excitation and shake-off, processes usually inaccessible by measurements of ionic yields only. The Ar7+ yield shows a clear deviation from the predictions of the commonly used model of sequential ionization via single-electron processes and the observed signal can only be explained by taking into account the full multiplet structure of the involved configurations and by inclusion of two-electron processes. The competing process of two-photon ionization from the ground state of Ar6+ is calculated to be orders of magnitude smaller

Is there an Olympic gold medal rush in the stock market?

Investor sentiment and attention are often linked to the same non-economic events making it difficult to understand why and how asset prices are affected. We disentangle these two potential drivers of investment behaviour by analysing a new dataset of medals for major participating countries and sponsor firms over four Summer Olympic Games. Existing studies focus only on investigating the effect of sports events and sentiment on stock market returns. We consider for the first time also the importance of investor attention and the effect on activity at the market and firm level. Our results show that trading volume and volatility is substantially reduced following Olympic success although returns appear to be largely unaffected. In the U.S., trading volume (realised volatility) during Olympics is over 24% (61%) lower than comparable periods of the year when Games do not take place. Each gold medal leads to a further decrease in volume of nearly 3% on average over the trading day following the award. These findings are in line with theories and evidence related to investor attention but cannot be easily explained on the basis of sentiment. Analysis of data from online search volumes and from surveys measuring investor sentiment, also suggest that the market impact of the Olympics is linked to changes in investor attention

Seasonality in the Athens stock exchange

This paper studies calendar effects in the emerging Athens Stock Exchange. Rather than examining only basket indices, we analyse calendar effects for each of the constituent stocks of the Athens Stock Exchange General Index for the period from October 1986 to April 1997. In accordance with similar studies substantial evidence of 'day-of-the week', 'monthly', 'trading month' and 'holiday' effects are found. The intensity of these effects for various stocks on the basis of capitalization, beta coefficients and company type are examined. The results indicate that the calendar regularities vary significantly across the constituent shares of the General Index and that aggregation introduces a considerable bias in unravelling these regularities. Also, it is found that factors such as the beta coefficient and company type influence significantly the intensity of calendar effects.

Creation of double ion hole states 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6, in dependence on the intensity

<p><strong>Figure 5.</strong> Creation of double ion hole states 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6, in dependence on the intensity.</p> <p><strong>Abstract</strong></p> <p>We present calculations on the multiple ionization of argon at the photon energy 123 eV and pulse duration 50 fs. At that photon energy, it is possible to drive the two-photon resonant Auger transition 2p → 4p, whose lifetime is 5.5 fs, much shorter than the pulse duration. The excitation of a 2p electron to the 4p state thus creates a hole which decays by an Auger process. We have also included above-threshold ionization from the outer shells of the neutral and singly ionized species, which becomes significant at intensities of the order of ~10¹⁵ W cm⁻² and higher. The populations of the various ionic species were obtained through the solution of the kinetic equations governing their production and decay during the pulse. The effect of the intensity distribution in the interaction volume has also been evaluated. We have further shown that doubly hollow ionic states of the type 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6 are created, which can decay only via spontaneous emission, with lifetimes orders of magnitude longer than the pulse duration. These hollow-ion states can potentially serve as a starting point for a variety of experimental investigations on doubly excited states.</p

Argon ionization products after volume integration

<p><strong>Figure 3.</strong> Argon ionization products after volume integration.</p> <p><strong>Abstract</strong></p> <p>We present calculations on the multiple ionization of argon at the photon energy 123 eV and pulse duration 50 fs. At that photon energy, it is possible to drive the two-photon resonant Auger transition 2p → 4p, whose lifetime is 5.5 fs, much shorter than the pulse duration. The excitation of a 2p electron to the 4p state thus creates a hole which decays by an Auger process. We have also included above-threshold ionization from the outer shells of the neutral and singly ionized species, which becomes significant at intensities of the order of ~10¹⁵ W cm⁻² and higher. The populations of the various ionic species were obtained through the solution of the kinetic equations governing their production and decay during the pulse. The effect of the intensity distribution in the interaction volume has also been evaluated. We have further shown that doubly hollow ionic states of the type 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6 are created, which can decay only via spontaneous emission, with lifetimes orders of magnitude longer than the pulse duration. These hollow-ion states can potentially serve as a starting point for a variety of experimental investigations on doubly excited states.</p

Outline of the paths of ionization

<p><strong>Figure 1.</strong> Outline of the paths of ionization. Note that for each transition channel, there are manifolds of fine structure states which have been accounted for in the calculation but are too many to be included in the figure.</p> <p><strong>Abstract</strong></p> <p>We present calculations on the multiple ionization of argon at the photon energy 123 eV and pulse duration 50 fs. At that photon energy, it is possible to drive the two-photon resonant Auger transition 2p → 4p, whose lifetime is 5.5 fs, much shorter than the pulse duration. The excitation of a 2p electron to the 4p state thus creates a hole which decays by an Auger process. We have also included above-threshold ionization from the outer shells of the neutral and singly ionized species, which becomes significant at intensities of the order of ~10¹⁵ W cm⁻² and higher. The populations of the various ionic species were obtained through the solution of the kinetic equations governing their production and decay during the pulse. The effect of the intensity distribution in the interaction volume has also been evaluated. We have further shown that doubly hollow ionic states of the type 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6 are created, which can decay only via spontaneous emission, with lifetimes orders of magnitude longer than the pulse duration. These hollow-ion states can potentially serve as a starting point for a variety of experimental investigations on doubly excited states.</p

Relaxation of the excited states of argon ions via spontaneous emission: (a) Ar⁺, (b) Ar^{2 +}, (c) Ar^{3 +}, (d) Ar^{4 +}, (e) Ar^{5 +} and (f) Ar^{6 +}

<p><strong>Figure 4.</strong> Relaxation of the excited states of argon ions via spontaneous emission: (a) Ar⁺, (b) Ar^{2 +}, (c) Ar^{3 +}, (d) Ar^{4 +}, (e) Ar^{5 +} and (f) Ar^{6 +}.</p> <p><strong>Abstract</strong></p> <p>We present calculations on the multiple ionization of argon at the photon energy 123 eV and pulse duration 50 fs. At that photon energy, it is possible to drive the two-photon resonant Auger transition 2p → 4p, whose lifetime is 5.5 fs, much shorter than the pulse duration. The excitation of a 2p electron to the 4p state thus creates a hole which decays by an Auger process. We have also included above-threshold ionization from the outer shells of the neutral and singly ionized species, which becomes significant at intensities of the order of ~10¹⁵ W cm⁻² and higher. The populations of the various ionic species were obtained through the solution of the kinetic equations governing their production and decay during the pulse. The effect of the intensity distribution in the interaction volume has also been evaluated. We have further shown that doubly hollow ionic states of the type 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6 are created, which can decay only via spontaneous emission, with lifetimes orders of magnitude longer than the pulse duration. These hollow-ion states can potentially serve as a starting point for a variety of experimental investigations on doubly excited states.</p

Overall yields of argon ions up to Ar^{7 +} under a Gaussian pulse of 50 fs duration and 123 eV photon energy

<p><strong>Figure 2.</strong> Overall yields of argon ions up to Ar^{7 +} under a Gaussian pulse of 50 fs duration and 123 eV photon energy. ATI leading to singly and doubly ionized argon has been included separately (dashed lines), as well as the Ar⁺ ions due to the Auger effect (dash–dotted line, green).</p> <p><strong>Abstract</strong></p> <p>We present calculations on the multiple ionization of argon at the photon energy 123 eV and pulse duration 50 fs. At that photon energy, it is possible to drive the two-photon resonant Auger transition 2p → 4p, whose lifetime is 5.5 fs, much shorter than the pulse duration. The excitation of a 2p electron to the 4p state thus creates a hole which decays by an Auger process. We have also included above-threshold ionization from the outer shells of the neutral and singly ionized species, which becomes significant at intensities of the order of ~10¹⁵ W cm⁻² and higher. The populations of the various ionic species were obtained through the solution of the kinetic equations governing their production and decay during the pulse. The effect of the intensity distribution in the interaction volume has also been evaluated. We have further shown that doubly hollow ionic states of the type 3s⁰3p^<em>n</em> with 2 ≤ <em>n</em> ≤ 6 are created, which can decay only via spontaneous emission, with lifetimes orders of magnitude longer than the pulse duration. These hollow-ion states can potentially serve as a starting point for a variety of experimental investigations on doubly excited states.</p