Phase-of-the-Phase Electron Momentum Spectroscopy on Single Metal Atoms in Helium Nanodroplets.

Magnesium atoms fully embedded in helium nanodroplets are exposed to two-color laser pulses, which trigger multiphoton above-threshold ionization (ATI). This allows exemplary study of the contribution of a dense, neutral, and finite medium on single electron propagation. The angular-resolved photoelectron spectra show striking differences with respect to results obtained on free atoms. Scattering of the individual Mg photoelectrons, when traversing the neutral helium environment, causes the angular distribution to become almost isotropic. Furthermore, the appearance of higher-energy electrons is observed, indicating the impact of the droplet on the concerted emission process. Phase-of-the-phase spectroscopy, however, reveals a marked loss in the 2ω-ω phase dependence of the electron signal. Taking into account sideband formation on a quantitative level, a Monte Carlo simulation which includes laser-assisted electron scattering can reproduce the experimental spectra and give insights into the strong-field-induced electron emission from disordered systems.

Screen Printed Antennas on Fiber-Based Substrates for Sustainable HF RFID Assisted E-Fulfilment Smart Packaging.

Intelligent packaging is an emerging technology, aiming to improve the standard communication function of packaging. Radio frequency identification (RFID) assisted smart packaging is of high interest, but the uptake is limited as the market needs cost-efficient and sustainable applications. The integration of screen printed antennas and RFID chips as smart labels in reusable cardboard packaging could offer a solution. Although paper is an interesting and recyclable material, printing on this substrate is challenging as the ink conductivity is highly influenced by the paper properties. In this study, the best paper/functional silver ink combinations were first selected out of 76 paper substrates based on the paper surface roughness, air permeance, sheet resistance and SEM characterization. Next, a flexible high frequency RFID chip (13.56 MHz) was connected on top of screen printed antennas with a conductive adhesive. Functional RFID labels were integrated in cardboard packaging and its potential application as reusable smart box for third party logistics was tested. In parallel, a web-based software application mimicking its functional abilities in the logistic cycle was developed. This multidisciplinary approach to developing an easy-scalable screen printed antenna and RFID-assisted smart packaging application is a good example for future implementation of hybrid electronics in sustainable smart packaging.

Nonlinearity-induced photonic topological insulator.

A hallmark feature of topological insulators is robust edge transport that is impervious to scattering at defects and lattice disorder. We demonstrate a topological system, using a photonic platform, in which the existence of the topological phase is brought about by optical nonlinearity. The lattice structure remains topologically trivial in the linear regime, but as the optical power is increased above a certain power threshold, the system is driven into the topologically nontrivial regime. This transition is marked by the transient emergence of a protected unidirectional transport channel along the edge of the structure. Our work studies topological properties of matter in the nonlinear regime, providing a possible route for the development of compact devices that harness topological features in an on-demand fashion.

High-Harmonic Generation in Solids with and without Topological Edge States.

High-harmonic generation in the two topological phases of a finite, one-dimensional, periodic structure is investigated using a self-consistent time-dependent density functional theory approach. For harmonic photon energies smaller than the band gap, the harmonic yield is found to differ by up to 14 orders of magnitude for the two topological phases. This giant topological effect is explained by the degree of destructive interference in the harmonic emission of all valence-band (and edge-state) electrons, which strongly depends on whether or not topological edge states are present. The combination of strong-field laser physics with topological condensed matter opens up new possibilities to electronically control strong-field-based light or particle sources or-conversely-to steer by all optical means topological electronics.

Radical quantum yields from formaldehyde photolysis in the 30,400-32,890 cm(-1) (304-329 nm) spectral region: detection of radical photoproducts using pulsed laser photolysis-pulsed laser induced fluorescence.

The relative quantum yield for the production of radical products, H + HCO, from the UV photolysis of formaldehyde (HCHO) has been measured using a pulsed laser photolysis­pulsed laser induced fluorescence (PLP­PLIF) technique across the 30,400­32,890 cm(­1) (304­329 nm) spectral region of the Ã(1)A2­X̃(1)A1 electronic transition. The photolysis laser had a bandwidth of 0.09 cm(­1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (0.07 cm(­1)), and the yield spectrum shows detailed rotational structure. The H and HCO photofragments were monitored using LIF of the OH radical as a spectroscopic marker. The OH radicals were produced by rapid reaction of the H and HCO photofragments with NO2. This technique produced an "action" spectrum that at any photolysis wavelength is the product of the H + HCO radical quantum yield and HCHO absorption cross section at the photolysis wavelength and is a relative measurement. Using the HCHO absorption cross section previously obtained in this laboratory, the relative quantum yield was determined two different ways. One produced band specific yields, and the other produced yields averaged over each 100 cm(­1). Yields were normalized to a value of 0.69 at 31,750 cm(­1) based on the current recommendation of Sander et al. (Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friedl, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K.; et al. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 17; Jet Propulsion Laboratory: Pasadena, CA, USA, 2011). The resulting radical quantum yields agree well with previous experimental studies and the current JPL recommendation but show greater wavelength dependent structure. A significant decrease in the quantum yield was observed for the 5(0)(1) + 1(0)(1)4(0)(1) combination band centered at 31,125 cm(­1). This band has a low absorption cross section and has little impact on the calculated atmospheric photodissociation rate but is a further indication of the complexity of HCHO photodissociation dynamics.

High-resolution absorption cross sections of formaldehyde in the 30,285-32,890 cm(-1) (304-330 nm) spectral region.

Absolute room temperature (294 ± 2 K) absorption cross sections for the Ã(1)A(2)-X̃(1)A(1) electronic transition of formaldehyde have been measured over the spectral range 30,285-32,890 cm(-1) (304-330 nm) using ultraviolet (UV) laser absorption spectroscopy. Accurate high-resolution absorption cross sections are essential for atmospheric monitoring and understanding the photochemistry of this important atmospheric compound. Absorption cross sections were obtained at an instrumental resolution better than 0.09 cm(-1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (∼0.07 cm(-1)) and so we were able to resolve all but the most closely spaced lines. Comparisons with previous data as well as with computer simulations have been made. Pressure broadening was studied for the collision partners He, O(2), N(2), and H(2)O and the resulting broadening parameters have been measured and increase with the strength of intermolecular interaction between formaldehyde and the collision partner. The pressure broadening coefficient for H(2)O is an order of magnitude larger than the coefficients for O(2) and N(2) and will contribute significantly to spectral line broadening in the lower atmosphere. Spectral data are made available as Supporting Information.

Spatial orienting of attention in stereo depth.

The aim of this study was to investigate the spatial orienting of visual attention in depth under purely stereoscopic viewing conditions. Random-dot stereograms were used to present disparity-defined target stimuli that were either validly or invalidly cued in depth. In separate tasks, participants responded either to the relative depth of the target (protruding vs. receding) or to its shape (square vs. diamond). Stimulus onset asynchronies (SOAs) between an uninformative exogenous cue and target were varied from 250 to 600 ms. For both tasks, mean response times (RTs) were shorter for validly than invalidly cued target depths and this RT advantage was essentially restricted to the shortest SOA of 250 ms. These results indicate that attention can be reflexively allocated to locations in stereo depth under conditions of low perceptual load, and independent of whether depth is relevant to the task or not.

Temperature and pressure dependent rate coefficients for the reaction of Hg with Br and the reaction of Br with Br: a pulsed laser photolysis-pulsed laser induced fluorescence study.

A pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to study the recombination of mercury and bromine atoms, Hg + Br + M --> HgBr + M (1) and the self-reaction of bromine atoms, Br + Br + M --> Br2 + M (2). Rate coefficients were determined as a function of pressure (200-600 Torr) and temperature (243-293 K) in nitrogen buffer gas and as a function of pressure (200-600 Torr) in helium buffer gas at room temperature. For reaction 1, kinetic measurements were performed under conditions in which bromine atoms were the reactant in excess concentration while simultaneously monitoring the concentration of both mercury and bromine. A temperature dependent expression of (1.46 +/- 0.34) x 10(-32) x (T/298)(-(1.86+/-1.49)) cm6 molecule(-2) s(-1) was determined for the third-order recombination rate coefficient in nitrogen buffer gas. The effective second-order rate coefficient for reaction 1 under atmospheric conditions is a factor of 9 smaller than previously determined in a recently published relative rate study. For reaction 2 we obtain a temperature dependent expression of (4.31 +/- 0.21) x 10(-33) x (T/298)(-(2.77+/-0.30)) cm6 molecule(-2) s(-1) for the third-order recombination rate coefficient in nitrogen buffer gas. The rate coefficients are reported with a 2sigma error of precision only; however, due to the uncertainty in the determination of absolute bromine atom concentrations and other unidentified systematic errors we conservatively estimate an uncertainty of +/-50% in the rate coefficients. For both reactions the observed pressure, temperature and buffer gas dependencies are consistent with the expected behavior for three-body recombination.

Kinetic and mechanistic studies of the recombination of OH with NO2: vibrational deactivation, isotopic scrambling and product isomer branching ratios.

The kinetics and mechanism of the three-body recombination of OH with NO2 were studied using a pulsed laser photolysis pulsed laser induced fluorescence technique. The rate coefficients for deactivation of vibrationally excited OH (v = 1-5) by NO2 were found to be independent of vibrational level with a value of (6.4 +/- 0.3) x 10(-11) cm3 molecule s (-1) at 298 K. The rate coefficient for reaction of 18OH with NO2 was measured and found to be much faster than for unlabeled OH with a "zero pressure" rate of 1 x 10(-11) cm3 molecule(-1) s(-1) at 298 K and 273 K. Observation of temporal profiles of 16OH and 18OH suggest that isotopic scrambling in the initially formed [H18ON16O2] complex is complete on the microsecond time scale of our experiments. The rate coefficient for reaction of unlabeled OH with NO2 was measured at 413 K in 400 Torr of He. Biexponential temporal profiles were obtained and are consistent with a 10 +/- 3% yield of the weakly bound HOONO isomer.

Temperature and pressure dependent rate coefficients for the reaction of Hg with Cl and the reaction of Cl with Cl: a pulsed laser photolysis-pulsed laser induced fluorescence study.

A pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to study the recombination of mercury and chlorine atoms, Hg + Cl + M --> HgCl + M (1), and the self-reaction of chlorine atoms, Cl + Cl + M --> Cl(2) + M (2). Rate coefficients were determined as a function of pressure (200-600 Torr) and temperature (243-293 K) in N(2) buffer gas and as a function of pressure (200-600 Torr) in He buffer gas at room temperature. For reaction (1) kinetic measurements were obtained under conditions in which either mercury or chlorine atoms were the reactant in excess concentration while simultaneously monitoring the concentration of both reactants. An Arrhenius expression of (2.2 +/- 0.5) x 10(-32) exp{(680 +/- 400)((1)/(T) - (1)/(298))} cm(6) molecule(-2) s(-1) was determined for the third-order recombination rate coefficient in nitrogen buffer gas. The effective second-order rate coefficient for reaction 1 under atmospheric conditions is much smaller than prior determinations using relative rate techniques. For reaction (2) we obtain an Arrhenius expression of (8.4 +/- 2.3) x 10(-33) exp{(850 +/- 470)((1)/(T) - (1)/(298))} cm(6) molecule(-2) s(-1) for the third-order recombination rate coefficient in nitrogen buffer gas. The rate coefficients are reported with a 2sigma error of precision only; however, due to the uncertainty in the determination of absolute chlorine atom concentrations we conservatively estimate an uncertainty of +/-50% in the rate coefficients. For both reactions the observed pressure, temperature, and buffer gas dependencies are consistent with the expected behavior for three-body recombination.