A long-term transport experiment has been performed on a bioactive calcium phosphate glass of the molar composition 30CaO*25Na2O*45P2O5 using the technique of bombardment induced ion transport (BIIT) with potassium as foreign bombarder ion. Ion transport due to gradients of the electrical potential and the concentration lead to incorporation of K+ and depletion of both Na+ and Ca++ by electrodiffusion in the forward direction. The resulting concentration profiles have been quantitatively analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The concentration profiles of the P+ and POx+ signals (x = 1–4) resemble those of the K+, Na+, and Ca++ signals, indicating a characteristic change of the local bonding situation. This is interpreted as an indirect hint of a change of local structure of the glass network. Because the concentration profiles imprinted by the BIIT constitute pronounced concentration gradients, these depletion profiles further evolve on a much longer time scale due to chemical diffusion (absence of electric potential gradients). The former depletion zone is partially refilled by chemical diffusion. At the same time, the structural changes of the glass network are demonstrated to be reversible. Numerical simulations on the basis of the coupled Nernst–Planck–Poisson equations allow one to derive the diffusion coefficients of sodium, potassium, and calcium for both cases, that is, electrodiffusion and chemical diffusion. The two experiments are sensitive to different aspects of the diffusion coefficients and thus are complementary. The analysis is sensitive to the concentration dependence of D(Na+) and D(Ca++) for the electrodiffusion and of D(K+) for the chemical diffusion. For the chemical diffusion of Na+ and Ca++ in the backward direction, D(Ca++) is larger than D(Na+), indicating that the extra sites occupied by Ca++ in the preceding electrodiffusion are energetically high-lying.

The transport of potassium through praseodymium-manganese oxide (PrMnO3; PMO) has been investigated by means of the charge attachment induced transport (CAIT) technique. To this end, potassium ions have been attached to the front side of a 250 nm thick sample of PMO. The majority of the potassium ions become neutralized at the surface of the PMO, while some of the potassium ions diffuse through. Ex situ analysis of the sample by time-of-flight secondary ion mass spectrometry (ToF-SIMS) reveals pronounced concentration profiles of the potassium, which is indicative of diffusion. Two diffusion coefficients have been obtained, namely, the bulk diffusion coefficient and the diffusion coefficient associated with the grain boundaries. The latter conclusion is supported by transmission electron microscopy of thin lamella cut out from the sample, which reveals twin grain boundaries reaching throughout the entire sample as well as model calculations.

The competition of Na+ ion versus K+ ion transport in a mixed alkali borosilicate glass has been investigated by low energy bombardment induced ion transport employing Cs+ ions as the foreign ion. Electrodiffusion causes the replacement of Na+ and K+ down to about 200 nm below the surface of the glass. Beyond this electrodiffusion front (in the direction of ion transport) K+ ions accumulate to a density above the bulk concentration while Na+ is further depleted towards the backside electrode. At the backside electrode only Na is electrodeposited since the electrical potential does not allow for K electrodeposition. A full simulation of the electrodiffusion profiles reveals the complete concentration dependence of the diffusion coefficients of the Na+ and K+ ions.

The dependence of the ionic conductance of ultra-thin polyelectrolyte multilayer (PEM) films on the temperature and the number of bilayers has been investigated by the recently developed low energy bombardment induced ion transport (BIIT) method. To this end multilayers of alternating poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) layers were deposited on a metal electrode and subsequently bombarded by a low energy potassium ion beam. Ions are transported through the film according to the laws of electro-diffusion towards a grounded backside electrode. They are neutralized at the interface between the polymer film and the metal electrode. The detected neutralization current scales linearly with the acceleration potential of the ion beam indicating Ohmic behavior for the (PAH/PSS)x multilayer, where x denotes the number of bilayers. The conductance exhibits a non-monotonic dependence on the number of bilayers, x. For 2 ≤ x ≤ 8 the conductance increases non-linearly with the number of bilayers. For x ≥ 8 the conductance decreases with increasing number of bilayers. The variation of the conductance is rationalized by a model accounting for the structure dependence of the conductivity. The thinnest sample for which the conductance has been measured is the single bilayer reflecting properties dominated by the interface. The activation energy for the ion transport is 0.49 eV.

•Demonstration of competing transport between monovalent K+ and divalent Ca++ in a calcium-phosphate glass•Generation of electrodiffusion profiles by means of foreign-ion BIIT•Quantification of depth profiles derived from ToF-SIMS•Quantitative theoretical description of electrodiffusion profiles•Demonstration that two monovalent Cs+ ions replace one Ca++ leading to an increase in the local particle density.•Discussion of this observation in relation to glass strenthening processes.The competing transport between K+ ions and Ca++ ions in a phosphate glass has been investigated by the low-energy bombardment induced ion transport (BIIT). To this end low energy Cs+ ions have been attached to the front side of the sample in contact with a single grounded electrode. Charging of the sample surface generates a gradient of the electrochemical potential and induces the corresponding transport of ions in the glass. Ex situ depth profiling reveals that both K+ and Ca++ are mobile in the glass. Both ions have been depleted and replaced by Cs+ ions. The quantitative analysis of the depth profiles in comparison with Nernst-Planck-Poisson calculations reveals that one Cs+ ion has replaced one K+ ion but two Cs+ ions have replaced one Ca++ ion. This ensures charge neutrality within the sample. It implies an increase in the local particle density in the diffusion zone above the original bulk value. The possible relevance of this non-conservation of particle density for chemical glass strengthening is discussed.

The self-reaction of state-selected HCl+ (DCl+) ions with HCl has been investigated in a guided ion beam setup. The absolute cross sections for proton transfer and deuteron transfer decrease with increasing center of mass collision energy, Ec.m.. The cross section for charge transfer (DCl+ + HCl) exhibits a maximum at Ec.m. = 0.5 eV. The cross section for PT and DT decrease significantly with increasing rotational angular momentum in the molecular ion, for the PT the cross section increases again for the highest angular momentum investigated. The rotational dependence of the cross section is rationalized by a simple model in which both the collision energy and part of the rotational energy are available for the reaction. The contribution of the rotation to the total energy available itself depends on the collision energy.

•Monte Carlo calculation of the time dependence of concentration profiles.•Evolution of electro-neutral depletion zones.•Electrons become mobile at the breakdown field strength.•Correlated transport of Na+ ions Ca2+ ions and electrons.•Rationalization of temporal sequentiality and limit thereof.A theoretical model for describing the time evolution of concentration profiles in thermal electro-poling experiments is being presented. The model is based on a Monte Carlo formalism. It takes into account the field dependent mobility of cations as well as electrons. Model calculations are presented for a 46S4 bio-glass. Upon application of a DC field Na+ ions start to move toward the cathode giving rise to a depletion zone. The electric field increases in this zone. Once a specific threshold value is reached the electrons become mobile and move toward the anode leaving behind a basically neutral zone. Thus, the full double layer capacity has developed after a few seconds. The concentration depletion profiles continue to develop on a much longer time scale of tens of minutes. In the 46S4 glass Na+ ions as well as Ca++ ions develop a depletion profile. The numerical calculations account for all essential experimental observations available in the literature. The model is also capable of predicting under which conditions two different cations move on the same or on different time scales.

The bombardment induced ion transport (BIIT) technique has been employed for studying the ionic conductivity of thin poly(p-xylylene) (PPX) films. The experiment is based on bombarding a PPX film with a c.w. potassium ion beam. The transport of ions through the film – which follows the laws of electrodiffusion – is detected as a neutralization current on the backside electrode on which the film has been deposited. This backside current scales quadratically with the acceleration potential of the ion beam and inversely cubically with the thickness of the film. This confirms theoretical predictions made in part I of this mini-series (Phys. Chem. Chem. Phys., 2011, 13, 20112–20122). This characteristic is markedly different from the Ohm-like current–voltage properties of a solid electrolyte, e.g. an ion conducting glass. The diffusion coefficient for K+ in PPX is determined to be 8.528 × 10−16 cm2 s−1 at 333 K. From the temperature dependence of the diffusion coefficient we conclude that a hopping mechanism with an activation energy of 2.74 eV ± 0.18 eV is operative.

•We manipulate surface region of ion conductor over ca. 50 nm.•We analyze and describe diffusion profiles quantitatively.•We demonstrate inhomogeneous diffusion coefficients.The bombardment of a sodium ion conductor with a low energy cesium ion beam is shown to induce ion transport in the sample, which involves the sodium as well as the cesium ions. This transport ultimately generates a macroscopic zone, where up to 95% of the sodium has been replaced by cesium. The zone where sodium and cesium coexist has been analyzed by means of the time-of-flight secondary-ion-mass-spectrometry. The experimental electro-diffusion profiles of the sodium and the cesium are quantitatively modeled by the Nernst–Planck–Poisson equations. The diffusion coefficient of the sodium is demonstrated to markedly depend on the local environment. It decreases by several orders of magnitude upon incorporation of the cesium ions.

The bombardment of condensed matter by low energy ion beams induces ion transport through the material. A general theory for bombardment induced ion transport (BIIT) based on numerical solutions of the well known Nernst–Planck–Poisson equations is presented. The theory is applicable to polymer membranes as well as ion-conducting glasses with the implementation of appropriate boundary conditions. The fundamental properties of the theory, i.e. the capability to describe the potential, the field and the concentration/charge density profile within the two classes of materials mentioned above are demonstrated. In particular, the theory is capable of describing experimental observables which will be further elaborated in part II of this miniseries.

Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D+ and Cl+ fragments were recorded via velocity-map imaging. A waveform-dependent anti-correlated directional emission of D+ and Cl+ fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl+ and in turn the directional emission of charged fragments upon the breakup of the molecular ion.

The circular dichroism (CD) induced by femtosecond laser pulse excitation of 3-methyl-cyclopentanone has been investigated by means of experiment and theory as a function of the laser pulse duration. In the experiment the CD in ion yields is measured by femtosecond laser ionization via a one-photon resonant excited state. In the theoretical part the CD is calculated by solving laser driven quantum electron dynamics for the same resonant excitation based on ab initio electronic structure calculations employing a complete description of the electric field–electric dipole and magnetic field–magnetic dipole interactions. Both the experimentally measured CD in ion yields and the calculated CD in excited state populations exhibit a marked increase of the CD for pulse duration increasing from 50 fs to about 200 fs. Beyond 200 fs pulse duration the CD levels off. The combination of experimental and theoretical evidences indicates that the CD decreases with increasing laser intensity connected to the increased coupling between the excited states.

A new experimental approach for measuring the ionic conductivity of solid materials is proposed. The experiment is based on bombarding an ion conducting sample with an alkali ion beam. This generates a well defined surface potential which in turn causes ion transport in the material. The ion transport is measured at the back side of the sample. The viability of the concept is demonstrated by measuring the temperature dependence of the potassium ion conductivity of a potassium borosilicate glass. The activation energy for the potassium transport is 1.04 eV ± 0.06 eV. For comparison, conductivity data obtained by impedance spectroscopy are presented, which support the bombardment induced data.

The bombardment of condensed matter by low energy ion beams induces ion transport through the material. A general theory for bombardment induced ion transport (BIIT) based on numerical solutions of the well known Nernst–Planck–Poisson equations is presented. The theory is applicable to polymer membranes as well as ion-conducting glasses with the implementation of appropriate boundary conditions. The fundamental properties of the theory, i.e. the capability to describe the potential, the field and the concentration/charge density profile within the two classes of materials mentioned above are demonstrated. In particular, the theory is capable of describing experimental observables which will be further elaborated in part II of this miniseries.

A new experimental approach for measuring the ionic conductivity of solid materials is proposed. The experiment is based on bombarding an ion conducting sample with an alkali ion beam. This generates a well defined surface potential which in turn causes ion transport in the material. The ion transport is measured at the back side of the sample. The viability of the concept is demonstrated by measuring the temperature dependence of the potassium ion conductivity of a potassium borosilicate glass. The activation energy for the potassium transport is 1.04 eV ± 0.06 eV. For comparison, conductivity data obtained by impedance spectroscopy are presented, which support the bombardment induced data.

Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D+ and Cl+ fragments were recorded via velocity-map imaging. A waveform-dependent anti-correlated directional emission of D+ and Cl+ fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl+ and in turn the directional emission of charged fragments upon the breakup of the molecular ion.

The circular dichroism (CD) induced by femtosecond laser pulse excitation of 3-methyl-cyclopentanone has been investigated by means of experiment and theory as a function of the laser pulse duration. In the experiment the CD in ion yields is measured by femtosecond laser ionization via a one-photon resonant excited state. In the theoretical part the CD is calculated by solving laser driven quantum electron dynamics for the same resonant excitation based on ab initio electronic structure calculations employing a complete description of the electric field–electric dipole and magnetic field–magnetic dipole interactions. Both the experimentally measured CD in ion yields and the calculated CD in excited state populations exhibit a marked increase of the CD for pulse duration increasing from 50 fs to about 200 fs. Beyond 200 fs pulse duration the CD levels off. The combination of experimental and theoretical evidences indicates that the CD decreases with increasing laser intensity connected to the increased coupling between the excited states.

The bombardment induced ion transport (BIIT) technique has been employed for studying the ionic conductivity of thin poly(p-xylylene) (PPX) films. The experiment is based on bombarding a PPX film with a c.w. potassium ion beam. The transport of ions through the film – which follows the laws of electrodiffusion – is detected as a neutralization current on the backside electrode on which the film has been deposited. This backside current scales quadratically with the acceleration potential of the ion beam and inversely cubically with the thickness of the film. This confirms theoretical predictions made in part I of this mini-series (Phys. Chem. Chem. Phys., 2011, 13, 20112–20122). This characteristic is markedly different from the Ohm-like current–voltage properties of a solid electrolyte, e.g. an ion conducting glass. The diffusion coefficient for K+ in PPX is determined to be 8.528 × 10−16 cm2 s−1 at 333 K. From the temperature dependence of the diffusion coefficient we conclude that a hopping mechanism with an activation energy of 2.74 eV ± 0.18 eV is operative.

The self-reaction of state-selected HCl+ (DCl+) ions with HCl has been investigated in a guided ion beam setup. The absolute cross sections for proton transfer and deuteron transfer decrease with increasing center of mass collision energy, Ec.m.. The cross section for charge transfer (DCl+ + HCl) exhibits a maximum at Ec.m. = 0.5 eV. The cross section for PT and DT decrease significantly with increasing rotational angular momentum in the molecular ion, for the PT the cross section increases again for the highest angular momentum investigated. The rotational dependence of the cross section is rationalized by a simple model in which both the collision energy and part of the rotational energy are available for the reaction. The contribution of the rotation to the total energy available itself depends on the collision energy.

The dependence of the ionic conductance of ultra-thin polyelectrolyte multilayer (PEM) films on the temperature and the number of bilayers has been investigated by the recently developed low energy bombardment induced ion transport (BIIT) method. To this end multilayers of alternating poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) layers were deposited on a metal electrode and subsequently bombarded by a low energy potassium ion beam. Ions are transported through the film according to the laws of electro-diffusion towards a grounded backside electrode. They are neutralized at the interface between the polymer film and the metal electrode. The detected neutralization current scales linearly with the acceleration potential of the ion beam indicating Ohmic behavior for the (PAH/PSS)x multilayer, where x denotes the number of bilayers. The conductance exhibits a non-monotonic dependence on the number of bilayers, x. For 2 ≤ x ≤ 8 the conductance increases non-linearly with the number of bilayers. For x ≥ 8 the conductance decreases with increasing number of bilayers. The variation of the conductance is rationalized by a model accounting for the structure dependence of the conductivity. The thinnest sample for which the conductance has been measured is the single bilayer reflecting properties dominated by the interface. The activation energy for the ion transport is 0.49 eV.

The transport of potassium through praseodymium-manganese oxide (PrMnO3; PMO) has been investigated by means of the charge attachment induced transport (CAIT) technique. To this end, potassium ions have been attached to the front side of a 250 nm thick sample of PMO. The majority of the potassium ions become neutralized at the surface of the PMO, while some of the potassium ions diffuse through. Ex situ analysis of the sample by time-of-flight secondary ion mass spectrometry (ToF-SIMS) reveals pronounced concentration profiles of the potassium, which is indicative of diffusion. Two diffusion coefficients have been obtained, namely, the bulk diffusion coefficient and the diffusion coefficient associated with the grain boundaries. The latter conclusion is supported by transmission electron microscopy of thin lamella cut out from the sample, which reveals twin grain boundaries reaching throughout the entire sample as well as model calculations.