Attosecond light pulse induced photo-association

We explore stimulated photo-association in the context of attosecond pump-probe schemes of atomic matter. An attosecond pulse -- the probe -- is used to induce photo-association of an electronic wave packet which had been created before, typically with an attosecond pump pulse at an atomic center different from the one of photo-association. We will show that the electron absorption is maximal for a certain delay between the pulses. Two ways of enhancing and controlling stimulated photo-association are proposed, namely using an additional infrared pulse to steer the electronic wave packet and using a train of attosecond pulses instead of a single pair. A direct application of ultrafast stimulated photo-association is the measurement of atomic distances.Comment: 7 pages, 8 figure

Autoionizing decay of H 2 doubly excited states by using xuv-pump-infrared-probe schemes with trains of attosecond pulses

We present a theoretical study of H2 ionization by a pump-probe scheme consisting on an attosecond pulse train (APT) and a near-infrared (IR) pulse.We focus on the autoionization dynamics of the first series of resonant states of the molecule, the Q1 doubly excited states. The APT central frequency is tuned to populate the 1∑ + u resonant states. The trace of autoionization is clearly visible in the two-dimensional (2D) proton-electron coincidence spectra and in the proton kinetic energy spectra. The dynamics of the autoionization process is clearly visible in the movie obtained by plotting the 2D spectrum as a function of the time delay between the APT and IR pulses. An analysis of the final symmetries ∑g and ∑u allows us to track the origin of the different structuresThis work was partially supported by the MICINN Projects No. FIS2010- 15127, No. ACI2008-0777, and No. CSD 2007-00010, the ERA-Chemistry Project No. PIM2010EEC-00751, the European grants MC-ITN CORINF and MC-RG ATTOTREND, the European COST Action CM0702, and the Advanced Grant of the European Research Council XCHEM 29085

Molecular Resolvent Operator for H2 + molecule

We present a theoretical method to extract photoelectron and nuclear kinetic energy spectra of molecules under intense ultrashort laser pulses. The method is applied to H2+ photoionization and dissociation within a 3D model of the H2+ molecule. This method is an extension to molecules of the resolvent technique originally proposed for atoms, which was recently implemented to extract absolute values of photoelectron and nuclear kinetic energy spectr

Molecular resolvent-operator method: Electronic and nuclear dynamics in strong-field ionization

We present an extension of the resolvent-operator method (ROM), originally designed for atomic systems, to extract differential photoelectron spectra (in photoelectron- and nuclear-kinetic energy) for diatomic molecules interacting with strong, ultrashort laser fields in the single active electron approximation. The method is applied to the study of H2+ photodissociation and photoionization by femtosecond laser pulses in the XUV-IR frequency range. In particular, the method is tested (i) in the perturbative regime, for few-photon absorption and bound-bound electronic transitions, and (ii) in the strong-field regime, in which multiphoton absorption and tunneling are present. In the latter case, we show how the differential ROM allows one to track the transition between both regimes. We also analyze isotopic effects by comparing the dynamics of H2+ and D2+ ionization for different pulses. © 2014 American Physical Society.This work was accomplished with an allocation of computer time from Mare Nostrum BSC and CCC-UAM and was partially supported by the MICINN Projects No. FIS2010- 15127 and No. CSD 2007-00010, ERA-Chemistry Project No. PIM2010EEC-00751, the European grants No. MC-ITN CORINF and No. MC-RG ATTOTREND, the European COST Action No. CM0702, and European Research Council Advanced Grant No. XCHEM 290853. R.E.F.S. acknowledges a Ph.D. contract from ITN CORINF and Grant No. SFRH/BD/84053/2012 from the Portuguese government. P.R. acknowledges a Juan de la Cierva contract grant from the Spanish MICIN

Correlated electron and nuclear dynamics in strong field photoionization of H2+

We present a theoretical study of H2+ ionization under strong IR femtosecond pulses by using a method designed to extract correlated (2D) photoelectron and proton kinetic energy spectra. The results show two distinct ionization mechanisms—tunnel and multiphoton ionization—in which electrons and nuclei do not share the energy from the field in the same way. Electrons produced in multiphoton ionization share part of their energy with the nuclei, an effect that shows up in the 2D spectra in the form of energy-conservation fringes similar to those observed in weak-field ionization of diatomic molecules. In contrast, tunneling electrons lead to fringes whose position does not depend on the proton kinetic energy. At high intensity, the two processes coexist and the 2D plots show a very rich behavior, suggesting that the correlation between electron and nuclear dynamics in strong field ionization is more complex than one would have anticipatedThis work was accomplished with an allocation of computer time from Mare Nostrum BSC and CCC-UAM, and was partially supported by the MICINN Projects No. FIS2010-15127, No. ACI2008-0777, and No. CSD 2007-00010, the ERA-Chemistry Project No. PIM2010EEC-00751, the European Grants No. MCITN CORINF and No. MC-RG ATTOTREND, the European COST Action CM0702, and the Advanced Grant of the European Research Council, Grant No. XCHEM 290853. R. E. F. S. acknowledges a Ph.D. contract from ITN CORINF. P. R. acknowledges a Juan de la Cierva contract grant from MICIN

Enhancing high-order harmonic generation in light molecules by using chirped pulses

One of the current challenges in high-harmonic generation is to extend the harmonic cutoff to increasingly high energies while maintaining or even increasing the efficiency of the high-harmonic emission. Here we show that the combined effect of down-chirped pulses and nuclear dynamics in light molecules allows one to achieve this goal, provided that long enough IR pulses are used to allow the nuclei to move well outside the Franck-Condon region. We also show that, by varying the duration of the chirped pulse or by performing isotopic substitution while keeping the pulse duration constant, one can control the extension of the harmonic plateauWe gratefully acknowledge fruitful discussions with Y.Mairesse. This work has been accomplished with a generous allocation of computer time from Mare Nostrum BSC and CCC-UAM and has been partially supported by the European Research Council Advanced Grant No. XCHEM 290853, MINECO Project No. FIS2013-42002-R, ERA-Chemistry Project No. PIM2010EEC-00751, European Grant No. MC-ITN CORINF, European COST Action XLIC CM1204, and the CAM project NANOFRONTMAG. R. E. F. S. acknowledges FCT—Fundação para a Ciência e Tecnologia, Portugal, Grant No. SFRH/BD/84053/201

Energy- and angle-resolved ionization of H2+ interacting with xuv subfemtosecond laser pulses

We present an extension of the resolvent operator method to extract fully differential ionization probabilities resulting from the interaction of ultrashort laser pulses with H2+ by including all electronic and vibrational (dissociative) degrees of freedom. The wave function from which ionization probabilities are extracted is obtained by solving the time-dependent Schrödinger equation in a grid for the case of H2+ oriented parallel to the polarization direction of the field. The performance of the method is illustrated by using pulses in the xuv domain. Correlated kinetic-energy (CKE) and correlated angular and nuclear kinetic-energy (CAKN) spectra have been evaluated and used to analyze the underlying mechanisms of the photoionization process. In particular, for pulses with a central frequency ω=0.8 a.u., which is smaller than the vertical ionization potential of H2+, we show the opening of the one-photon ionization channel by decreasing the pulse duration down to less than 1 fs. An analysis of the CKE and CAKN spectra allows us to visualize individual contributions from one- and two-photon ionization processes, as well as to study the variation of these contributions with pulse duration. The latter information is difficult to extract when only the kinetic energy release (KER) spectrum is measured. This points out the importance of performing multiple-coincidence measurements for better elucidation of competing ionization mechanisms, such as those arising when ultrashort pulses are usedWe gratefully acknowledge fruitful discussions with Dr. A. Palacios. This work was accomplished with an allocation of computer time from Mare Nostrum BSC and CCCUAM and was partially supported by European Research Council Advanced Grant No. XCHEM 290853, MINECO Project No. FIS2013-42002-R, ERA-Chemistry Project No. PIM2010EEC-00751, European Grant No. MC-ITN CORINF, European COST Action XLIC CM1204, and the CAM project NANOFRONTMAG. H.B. acknowledges support for mobility from ITN CORINF and is grateful for the hospitality of the Universidad Autónoma de Madrid. R.E.F.S. acknowledges FCT - Fundacao para a Ciencia e Tecnologia, Portugal, Grant No. SFRH/BD/84053/201

Virtual single-photon transition interrupted: time-gated optical gain and loss

The response of matter to an optical excitation consists essentially of absorption and emission. Traditional spectroscopy accesses the frequency-resolved and time-integrated response, while the temporal evolution stays concealed. However, we will demonstrate here that the temporal evolution of a virtual single-photon transition can be mapped out by a second pulsed electromagnetic field. The resulting optical signal shows previously unexpected optical gain and loss, which can be gated and controlled via the relative delay of the electromagnetic fields. The model presented here can be applied to any system that assumes a two-level character through near-resonant optical dipole excitation, whether they are of atomic, molecular or even solid-state nature. These theoretical observations are in excellent qualitative agreement with our transient absorption spectroscopy study in helium. The presented results can act as starting point for a new scheme for creating optical gain, which is a prerequisite for the operation of lasers. It may be possible to open the doors to spectral regions, which were difficult to access until now, e.g. in the extreme ultraviolet.Comment: 15 pages, 4 figure

Standby and Off-Mode Energy Losses In New Appliances Measured in Shops

Selina project website at http://selina-project.eu PDF available online at http://selina-project.eu/files/SELINA_book.pdfInternational audienceThis document provides an overview of the most important results of the Intelligent Energy Europe (IEE) Project SELINA - Standby and Off-Mode Energy Losses In New Appliances Measured in Shops. Standby power is a general term commonly used to describe the low power modes in which many electrical and electronic products are, when not performing their main function. For more than a decade, it has been recognized that the energy consumption in low power modes for electrical and electronic products is an important issue because it represent permanent loads (sometimes up to 24 hours per day) of a huge number of products. With the 1 W standby initiative of the International Energy Agency (IEA), several low power mode measurement campaigns have been led on a regular basis in a number of countries outside and inside Europe Union (EU). Based on these results and on the Energy-using Products Study Lot 6, the EU has prepared new regulation to limit the standby and off-mode power consumption of non-networked household electronic and electrical equipment, which is being applied since January 2010. The IEE project SELINA carried out a large scale monitoring campaign in shops in order to characterise the low power modes of new appliances being sold in the EU market. In order to ensure consistency of the collected data, a common measurement methodology was developed and the same high resolution measurement equipment was used by all partners. This document analyzes the results of more than 6000 different equipments measured in the 12 EU countries involved in the project. Standby and off-mode values by product categories were analysed and compared with data from other regions of the World. The measurements were also benchmarked against the new 2010/2013 EU standby and off mode regulation thresholds and the impact of the EU regulation is discussed. It was found that 18.5% of the equipments, whose off-mode power was measured, do not respect the EU regulation threshold of 1 W. When the measurements are compared to the 2013 threshold of 0.5 W, this percentage raises up to 41.5%. Regarding standby mode input power, 31% of the measured products did not comply with EU regulation limit for the 2010 threshold. When the standby measured values are compared to the 2013 limit, the number of products over the EU regulation target increases to 66.4%. When comparing the 2009 and 2010 measurements, only a slight decrease of the share of appliances exceeding the EU regulation limits was observed. In parallel with the measurement campaign, an awareness study of the retailers was carried out. This survey helps to understand the customers' buying motivations and the influence of retailers' advice in their choices. The results of the survey show that, despite of retailer's consciousness about the energy consumption and energy labels of the products, other types of sales arguments like the appliance price or functionalities are more frequently used to sell a product. This could be due to lack of visible information in shops related to the equipment energy consumption. Furthermore, the results show that retailers try to adapt their advice to the customers' needs (price and product functionalities). The retailers admitted that publishing more information regarding the energy consumption of products and some kind of cost saving calculator/reference would make the clients to opt for more efficient equipments. Based on the survey results and on the analysis of different existing policies targeting electrical and electronic products in Europe, examples of policies to improve the low power modes situation of the EU market are reviewed. The survey on measures enhancing the market transformation towards more energy-efficient electrical appliances showed a wide range of actions and policy tools in the SELINA partner countries. In national workshops, which mainly took place in the late summer/early autumn 2010, these measures were presented and discussed with all relevant national stakeholders. In most countries, information campaigns (esp. brochures, leaflets, websites, and national labels) are the dominating measure type. In some countries, however, financial subsidies for very energy-efficient appliances, often paid by an energy utility and not by the government, play an important role, too (e.g. in the Czech Republic or Switzerland). In general, the impact of a financial programme is easier to quantify than the single impact of an information campaign, which often serves as an accompanying measure for regulations (labels, minimum efficiency standards) or fiscal and financial measures. International cooperation with key institutions outside the EU, involved in similar efforts, such as the IEA Implementing Agreement 4E (Efficient Electrical End-use Equipment) with an Annex on Standby, the Energy Star/EPA in USA, the Australia Standby Initiative and the Swiss Federal Office of Energy, were used to promote synergies in the definition of common approaches to characterize the market and to define realistic and cost-effective performance targets which can be achieved in a short time frame. Special care is required when promoting low standby consumption products (without consideration of other attributes) to ensure that there are no perverse effects such as the inadvertent promotion of products with low active mode efficiency and high energy consumption. It is desirable to follow a vertical approach to standby, where low power modes are combined with active modes to give total energy consumption. This approach is particularly preferable for products where the total energy consumption is significant. The definition of usage patterns under such a vertical approach is necessarily product specific and this could vary by region or country. The new technologies offer many opportunities for energy savings potential but there are also some threats which need to be recognized and understood. There is a strong need to ensure that energy saving paradigms and strategies become a core consideration in future product designs. It is recognized that equipments connected to networks are of growing importance. It is recommended that increased efforts to compile data and measurements, of networked products, from a variety of sources in order to obtain better information on networked product characteristics, needs to be made. An online database was created so that everyone can access the input power values, in the different equipment low power modes, of the more than 6000 equipments measured. A Standby Calculator Tool was also developed and can be accessed through the project website. It can be used to calculate the consumed energy, the annual cost and the equivalent CO2 emissions. In order to compare the results in an easy way, a diagram that shows the energy consumption of the different models is presented. Furthermore, the values for the most efficient device are also showed, in order to have an additional comparison. One of the main objectives of this project was to identify effective market transformation policies initiatives targeted at all the key stakeholders involved in the manufacture, distribution, sales, purchasing and operation of appliances with standby and off-mode losses. As a result of the future policy actions that may appear after the end of the project, considering loads in networked mode, it is expected to achieve very large cost-effective savings of electricity (80 TWh projected by 2020) and carbon emissions (30 MTons of CO2 by 2020)

Health and economic burden of sugar-sweetened beverages consumption in Brazil

Sugar-sweetened beverages (SSBs) are a major source of added sugar and are associated with noncommunicable diseases (NCDs) such as obesity and diabetes. This study assessed the impact of SSBs consumption on disease burden in Brazil, including deaths, disability-adjusted life years (DALYs), and healthcare costs. A 3-stage methodology was used to assess the direct effects of SSBs on diabetes, cardiovascular diseases, and body mass index (BMI), along with the influence of BMI on disease incidence. These assessments were then used to estimate the economic and health burden using population-attributable factors. Results showed that 2.7% and 11% of adult and children overweight/obesity cases were attributable to SSBs, respectively. SSBs consumption in Brazil led to 1,814,486 cases, 12,942 deaths, 362,088 DALYs, and USD 2,915.91 million in medical costs related to diabetes, cardiovascular diseases, oncological diseases, and other NCDs. Urgent implementation of public policies is crucial to address the consumption of SSBs, recognized as a key risk factor for NCDs