Helium migration in palladium I. Concentration dependence of helium release

Abstract

High temperature gas release from helium-implanted palladium has been investigated for He/Pd atom fractions from 5 × 10^?6 to 5 × 10^?2. The temperature required for 25 per cent He release increases with increasing dose to an atom fraction of 10^?4, where a sudden reversal occurs for higher concentrations. The release is associated with dramatic changes in the surface features of the palladium. A qualitative physical model is presented to explain the data.     

The stability of gadolinium-based contrast agents in human serum: A reanalysis of literature data and association with clinical outcomes

PurposeTo reanalyze literature data of gadolinium (Gd)-based contrast agents (GBCAs) in plasma with a kinetic model of dissociation to provide a comprehensive assessment of equilibrium conditions for linear GBCAs.MethodsData for the release of Gd from GBCAs in human serum was extracted from a previous report in the literature and fit to a kinetic dissociation/association model. The conditional stabilities (logK_cond) and percent intact over time were calculated using the model rate constants. The correlations between clinical outcomes and logK_cond or other stability indices were determined.ResultsThe release curves for Omniscan®, gadodiamide, OptiMARK®, gadoversetamide Magnevist® and Multihance® were extracted and all fit well to the kinetic model. The logK_conds calculated from the rate constants were on the order of ~ 4–6, and were not significantly altered by excess ligand or phosphate. The stability constant based on the amount intact by the initial elimination half-life of GBCAs in plasma provided good correlation with outcomes observed in patients.ConclusionsEstimation of the kinetic constants for GBCA dissociation/association revealed that their stability in physiological fluid is much lower than previous approaches would suggest, which correlates well with deposition and pharmacokinetic observations of GBCAs in human patients.     

Modeling of ion-assisted deposition using BCA computer simulation

Abstract

TRIM type binary collision approximation event store codes have employed to simulate collisional effects which occur during ion-beam or plasma assisted deposition of thin films.

Calculations can been performed using simplifying rate equation models, into which yields obtained from static TRIM simulations are inserted. Alternatively, the dynamic-composition code TRIDYN allows direct and complete simulations of the time-dependent processes.

Results are shown for different processes of ion-beam assisted deposition (IBAD), ion-beam mixing (IBM) post-treatment, and plasma-enhanced chemical vapour deposition (PECVD). Simulations of the formation of boron nitride films deposited from evaporated boron and energetic nitrogen show an excellent agreement with experimental results for nitrogen concentrations below the stoichiometric limit. For high N/B flux ratios, non-collisional mechanisms (ion-induced outdiffusion, surface trapping of outdiffusing nitrogen) have been included in the simulations, again producing good agreement with the experimental results. The ion-induced interface mixing of boron films on iron substrates is compared to experimental adhesion studies both for Ar⁺ post-treatment and Ar⁺ bombardment during deposition, demonstrating that the final adhesion is also influenced by other than purely collisional mechanisms. A special version of TRIDYN is used to treat the ion-induced densification of carbon films grown during simultaneous Ne⁺ bombardment, with reasonable agreement with experimental results. Finally, simple models are evaluated for the growth, composition and structure of C:H films grown in methane plasmas. The hydrogen content of the films decreases with increasing ion energy due to ion-induced release of hydrogen. Attempts to understand their bonding structure, in terms of the sp³/sp² ratio, on the basis of ion-induced preferential displacement, fail with respect to the energy dependence.     

Encapsulation and controlled release from core–shell nanoparticles fabricated by plasma polymerization

Core–shell nanostructures have been synthesized by plasma deposition in radio-frequency plasma reactor. Silica and KCl nanoparticles were encapsulated by deposition of isopropanol-based films of amorphous hydrogenated carbon. Through control of the deposition time, under constant deposition rate of 1 nm/min, particles are encapsulated in a layer of plasma polymer with thickness between 15 and 100 nm. Films are robust, chemically inert, thermally stable up to 250°C. The permeability of the shells is determined by depositing films of various thickness onto KCl nanoparticles and monitoring the dissolution of the core in aqueous solution. The dissolution profile is characterized by an initial rapid release, followed by a slow release that lasts up to 30 days for the thickest films. The profile is analyzed by Fickian diffusion through a spherical matrix. We find that this model captures very accurately the entire release profile except for the first 12 hours during which, the dissolution rate is higher than that predicted by the model. The overall diffusion coefficient for the dissolution of KCl is 3 × 10⁻²¹ m²/s.     

Saisonale Variation von Deuterium und Sauerstoff-18 in Luftfeuchte und Niederschlag über Antarktika

Abstract

D and ¹⁸O distributions were investigated in Antarctic precipitation (falling snow) and in water vapour to study their dependance on season and sampling site. Long-term sampling at the former German Georg Forster Station during 1978–93 and at the Japanese Syowa Station during 1994–97 allow conclusions about the present seasonal isotopic variations in the water inflow to Antarctica. The δD and δ¹⁸O values of precipitation at these East Antarctic coastal stations were compared with corresponding data from the West Antarctic Georg von Neumayer and Halley stations. The monthly means of these long-term data sets show typical hysteresis-like seasonal patterns of isotopic composition. Significant time lags exist regarding station temperatures, while water vapour δD values do not show such hysteresis patterns. Here, half-yearly and even quarter-yearly time components were found by Fourier analysis. Attempts were made to describe the variation in δD and δ¹⁸O values of water vapour and precipitation as well as in the resulting deuterium excess by the mixed cloud isotopic model (MCIM) of Ciais and Jouzel.     

Continuous thoron gas measurement using single scintillation cell – Correction for 212Pb deposition

Scintillation cells are used in continuous mode for thoron estimation using gross alpha counts. Such methods give rise to overestimation resulting from buildup of background counts due to the deposition of Lead (²¹²Pb). Here, the background counts in the cell for a specific counting period owing to previously deposited ²¹²Pb has been estimated using a model to get a time dependent correction factor. This correction for ²¹²Pb deposition has been utilized to estimate the current thoron concentration of the sample. The concentration obtained by this method is validated using the scintillation cell by grab sampling method and a continuous thoron monitor, RAD7.     

Electron-electron bound states in Maxwell-Chern-Simons-Proca QED <Emphasis Type="Bold">3</Emphasis>

We start from a parity-breaking MCS QED₃ model with spontaneous breaking of the gauge symmetry as a framework for evaluation of the electron-electron interaction potential and for attainment of numerical values for the e ^- e ^- - bound state. Three expressions ( V _eff , V _eff , V _eff ) are obtained according to the polarization state of the scattered electrons. In an energy scale compatible with condensed matter electronic excitations, these three potentials become degenerated. The resulting potential is implemented in the Schr?dinger equation and the variational method is applied to carry out the electronic binding energy. The resulting binding energies in the scale of 10-100 meV and a correlation length in the scale of 10-30 ? are possible indications that the MCS-QED₃ model adopted may be suitable to address an eventual case of e ^- e ^- pairing in the presence of parity-symmetry breakdown. The data analyzed here suggest an energy scale of 10-100 meV to fix the breaking of the U (1)-symmetry. Received 24 September 2002 / Received in final form 15 January 2003 Published online 1st April 2003 RID="a" ID="a"e-mail: belich@cbpf.br RID="b" ID="b"e-mail: delcima@cbpf.br RID="c" ID="c"e-mail: manojr@cbpf.br RID="d" ID="d"e-mail: helayel@cbpf.br     

Reconstruction of randomly under-sampled spectra for in vivo 13C magnetic resonance spectroscopy

PurposeOver the past decade, many techniques have been developed to reduce radiofrequency (RF) power deposition associated with proton decoupling in in vivo Carbon-13 (¹³C) magnetic resonance spectroscopy (MRS). In this work we propose a new strategy that uses data under-sampling to achieve reduction in RF power deposition.Materials and methodsEssentially, proton decoupling is required only during randomly selected segments of data acquisition. By taking advantage of the sparse spectral pattern of the carboxylic/amide region of in vivo ¹³C spectra of brain, we developed an iterative algorithm to reconstruct spectra from randomly under-sampled data. Fully sampled data were used as references. Reconstructed spectra were compared with the fully sampled references and evaluated using residuals and relative signal intensity errors.ResultsNumerical simulations and in vivo experiments at 7 Tesla demonstrated that this novel decoupling and data processing strategy can effectively reduce decoupling power deposition by greater than 30%.ConclusionThis study proposes and evaluates a novel approach to acquire ¹³C data with reduced proton decoupling power deposition and reconstruct in vivo ¹³C spectra of carboxylic/amide metabolite signals using randomly under-sampled data. Because proton decoupling is not needed over a significant portion of data acquisition, this novel approach can effectively reduce the required decoupling power and thus SAR. It opens the possibility of performing in vivo ¹³C experiments of human brain at very high magnetic fields.     

On the R2⁎ relaxometry in complex multi-peak multi-Echo chemical shift-based water-fat quantification: Applications to the neuromuscular diseases

PurposeInvestigation of the feasibility of the R₂^⁎ mapping techniques by using latest theoretical models corrected for confounding factors and optimized for signal to noise ratio.Theory and methodsThe improvement of the performance of state of the art magnetic resonance imaging (MRI) relaxometry algorithms is challenging because of a non-negligible bias and still unresolved numerical instabilities. Here, R₂^⁎ mapping reconstructions, including complex fitting with multi-spectral fat-correction by using single-decay and double-decay formulation, are deeply studied in order to investigate and identify optimal configuration parameters and minimize the occurrence of numerical artifacts. The effects of echo number, echo spacing, and fat/water relaxation model type are evaluated through both simulated and in-vivo data. We also explore the stability and feasibility of the fat/water relaxation model by analyzing the impact of high percentage of fat infiltrations and local transverse relaxation differences among biological species.ResultsThe main limits of the MRI relaxometry are the presence of bias and the occurrence of artifacts, which significantly affect its accuracy. Chemical-shift complex R₂^⁎-correct single-decay reconstructions exhibit a large bias in presence of a significant difference in the relaxation rates of fat and water and with fat concentration larger than 30%. We find that for fat-dominated tissues or in patients affected by extensive iron deposition, MRI reconstructions accounting for multi-exponential relaxation time provide accurate R₂^⁎ measurements and are less prone to numerical artifacts.ConclusionsComplex fitting and fat-correction with multi-exponential decay formulation outperforms the conventional single-decay approximation in various diagnostic scenarios. Although it still lacks of numerical stability, which requires model enhancement and support from spectroscopy, it offers promising perspectives for the development of relaxometry as a reliable tool to improve tissue characterization and monitoring of neuromuscular disorders.     

Diffusion Kinetics of Vitamin B12 from Alginate and Poly(vinyl acetate) Based Gel Scaffolds for Targeted Drug Delivery

Abstract

The research described here probed the thermodynamics and kinetics of Vitamin B₁₂ release from two types of polymeric gel scaffolds for targeted drug delivery applications. The polymeric gel scaffolds were successfully prepared from sodium alginate and polyvinyl acetate (PVA) using crosslinking and casting mechanisms, respectively. Vitamin B₁₂ was effectively blended into the polymeric gel scaffolds during their synthesis processes. The release of Vitamin B₁₂ from the polymeric gel scaffolds was characterized by immersing the scaffolds in a brine solution at various temperatures (25?°C, 32?°C and 37?°C) and, simultaneously, the transient concentrations were measured using a UV visible spectrophotometer. The sodium alginate gel scaffolds exhibited a more rapid release of Vitamin B₁₂ as compared to the PVA gel scaffolds. The Vitamin B₁₂ release kinetics from the alginate and PVA scaffolds were characterized by fitting the experimental data with various diffusion kinetic models. The Vitamin B₁₂ release from the alginate gel scaffolds followed the Peppas-Sahlin model, whereas releases from the PVA gel scaffolds were fitted to the Hopfenberg model. The diffusion coefficients for the alginate scaffolds with respect to the three temperatures were found to be 15.72?m²/s, 17.17?m²/s and 18.58?m²/s respectively whereas the diffusion coefficients for the PVA scaffolds with respect to the three temperatures were found to be 0.23?m²/s, 0.29?m²/s and 0.32?m²/s respectively. The activation energies (E_a) for the two types of polymeric scaffolds were calculated using the Stannett equation and found to be 10.38?kJ.mol^?1 and 20.47?kJ.mol^?1 for the alginate and PVA scaffolds, respectively, for all three temperatures.     

SiC bonding in ( C 60 ) n Si m clusters

This paper deals with a new type of SiC bonding where silicon atom seems to bridge C₆₀ molecules. We have studied films obtained by deposition of (C₆₀)_nSi_m clusters prepared in a laser vaporization source. Prior deposition, free ionized clusters were studied in a time-of-flight mass spectrometer. Mixed clusters (C₆₀)_nSi_m were clearly observed. Abundance and photofragmentation mass spectroscopies revealed the relatively high stability of the (C₆₀)_nSi _n ⁺ , (C₆₀)_nSi _{n - 1} ⁺ and (C₆₀)_nSi _{n - 2} ⁺ species. This observation is in favor of the arrangement of these complexes as polymers where the C₆₀ cages may be bridged by a silicon atom. Free neutral clusters are then deposited onto substrate making up a nanogranular thin film (≃ 100 nm). The film is probed by Auger and X-ray photoemission spectroscopies, but above all by surface enhanced Raman scattering. The results suggest an unusual chemical bonding between silicon and carbon and the environment of the silicon atom is expected to be totally different from the sp³ lattice: ten or twelve carbon neighbors might surround silicon atom. The bonding is discussed to the light of the so-called fullerene polymerization as observed for pure fullerite upon laser irradiation. This opens a new route for bridging C₆₀ molecules together with an appreciable energy bonding, since the usual van der Waals bonding in fullerite could be replaced by an ionocovalent bond. Such an assumption must be checked in the future by XAS and EXAFS experiments. Received 15 November 2000     

The role of OH ions in the stabilization of F colour centres in LiF

Thermally Stimulated Depolarisation Current (TSDC) and optical methods are applied to a range of alkali-fluoride crystals in order to establish a model for the stable F ₂ ⁺ - like colour centres in LiF:OH^-. The experimental results for LiF:OH^- suggest that the OH^- defects are partially destroyed under ionising irradiation or during crystal growth. The low-temperature dielectric relaxation signals in LiF:OH^- and LiF:Mg²⁺,OH^- are attributed to highly interacting hydroxide ions and products of their destruction located in extended lattice defects. In LiF:OH^-, in contrast to other alkali halides, the results advocate for a defect-structure model, which considers a neutral defect (ND, probably O₂ or H₂) sited at the anion vacancy of the O^2--V _a ⁺ dipole and which possibly is the “nucleus” for the F ₂ ⁺ centre. The proposed F ₂ ⁺ (ND, O^-) model seems to better explain the dielectric results, compared to the older F ₂ ⁺ (O^2-) and F ₂ ⁺ (O^-) models. The estimate for the electric dipole moment derived from the experimental TSDC bands, gives a value for the F ₂ ⁺ - like centre in LiF:OH^- between those of the F ₂ ⁺ (O^-) and F ₂ ⁺ (O^2-) defects, in good agreement with the proposed F ₂ ⁺ (ND,O^-) model. The reduction of the activation energy barrier of the (re)orientation process of the Mg²⁺V _c ^- (OH^-) complexes in LiF:Mg²⁺,OH^-, and the low-temperature shift of their TSDC band, compared to the single Mg ₂ ⁺ V _c ^- peak in LiF:Mg²⁺, are tentatively ascribed to an increase in the crystal-lattice parameters owing to the presence of OH^- and/or products of its destruction. Received 31 August 2001 / Received in final form 30 March 2002 Published online 9 July 2002     

Airborne Nitrogen Input at Four Locations in the German State of Saxony-Anhalt - Measurements using the 15N-Based ITNI-System

Abstract

The amount of atmospheric N deposition in Germany is actual rather uncertain. Estimates using standard methods indicate an N deposition of 30–35 kg N/ha × year. However, the results of long-term field experiments and newly by the ITNI (Integrated Total Nitrogen Input) system could prove a much higher N input of about 50–60 kg N/ha × year. The reason for this difference is that standard methods use wet-only or bulk collectors, which neglect gaseous and organic N deposition as well as direct N uptake by aerial plant parts. By contrast, the ITNI-system is able to measure the total atmospheric N input using the ¹⁵N isotope dilution method. The input of airborne N into a soil/plant system leads to a dilution of the abundance of a previously applied ¹⁵N tracer over a defined time period. The atmospheric N deposition can be calculated from this dilution.

To estimate the actual N input in Central Germany, ITNI measurements were carried out from autumn 1998 to autumn 2000 at four locations in the German state of Saxony-Anhalt. Atmospheric N depositions between 45 and 75 kg N/ha × year were determined depending on the location. These results closely match to N balances of longterm field experiments. Furthermore, a relationship was found between N deposition and the plant species used as well as plant development.     

Pressure dependence of the absorption edge at the E0 gap of mocvd - Grown ZnTe films

Abstract

We have investigated the direct gap absorption of 1μm thick ZnTe-epilayers grown on GaAs substrates by metalorganic chemical vapour deposition (MOCVD). Free ZnTe-layers were obtained by selective etching. The absorption coefficient was measured up to about 50000 cm^?1 in a diamand anvil cell in the temperature range from 115–300 K. The spectra near the direct gap E₀ are dominated by a sharp excitonic structure. Its change with pressure is evaluated by a model which allows to determine the pressure shift of the gap energy dE₀/dP and the change of the Rydberg energies of the excitons dR*/dP.^[1]     

A simple model of Cs-137 profile to estimate soil redistribution in cultivated stony soils

A main issue in soil erosion studies is to calibrate ¹³⁷Cs data to provide satisfactory estimates of erosion and deposition rates. The cultivation on steep slopes in some areas of the South Central Pyrenees results in serious affections to soils due to water erosion that mobilizes soil particles down slope. In the region, the intensive soil use including deforestation, overgrazing and extensive agriculture during the last centuries together with some characteristics of the soils such as poor development, thin soil profiles and high stone contents make them prone to erosion. A model based on ¹³⁷Cs profile is proposed to calculate erosion or sedimentation rates in these cultivated soils. The model uses parameters such as the volume of the fine fraction of the soils and the depth of cultivation calculated from the values obtained just from the soil sampling. Using a computer program the annual deposit of ¹³⁷Cs is simulated for an erosion or deposition rate of soil. To test the model, ¹³⁷Cs profiles of cultivated soils were collected at sampling sites located on temperate slopes in the Sierra de la Carrodilla (South Pyrenees) and experimental results were simulated with the model. The simulation results of the model were consistent with the experimental results of ¹³⁷Cs concentrations and inventories. The model offers a potential to describe the soil redistribution in stony soils and estimates of erosion and deposition rates can be calculated easily for a range of the most common soils found in Mediterranean environments.     

Ion bombardment induced phase transformations and inert gas mobility in the semiconductors Ge,Si, and GaAs

Abstract

The present study contributes some new aspects to the general understanding of the ion implantation behaviour of 3 common semiconductor materials, and of diffusion processes in these materials. Single crystals of Si, Ge, and GaAs were bombarded with Kr- or Xe-ions at energies of 40 or 500 keV and doses between 10¹¹ and 2 × 10¹⁶ ions/cm². Gas release measurements and Rutherford scattering of 1 MeV He⁺-ions combined with channeling were used to study bombardment damage (amorphization) and inert gas diffusion. At low bombardment doses (10¹¹ ions/cm²) and energy (40 keV), no damage was observed and the gas release was compatible with volume diffusion resembling Group I and VIII behaviour. Hence, the pre-exponential terms, D ₀, were low (range 10-^5±1 cm² sec^?1) and the activation enthalpies, Δ H, were much lower than those of self-diffusion or of diffusion of Group III and V elements. The Δ H's for gas diffusion followed the relation Δ H = (1.05±0.1) × 10^?3 T_m eV with the melting point, T_m , in °K. The mechanism of gas mobility might be the Turnbull dissociative mechanism. Rutherford scattering and channeling data indicated that part of the gas occupied lattice sites.

At higher doses, the bombarded layers turned amorphous. Channeling experiments showed a coincidence in temperatures for a gas release process different from the above one of volume diffusion, and recrystallization of the disordered layer to the single crystalline state. Both processes occurred in the temperature range 0.60 to 0.65 T_m . The gas release indicated a (partial) single jump character with implied Δ H's following the relation Δ H = (2.1±0.1) × 10^?3 T_m eV. Contrary to previous results on oxides, this new gas release occurred at temperatures near to those or even above those of volume diffusion of the gas.

Due to the easy formation of an amorphous layer it was difficult to observe the retarded release (trapping of gas) that has been found in many materials at high gas and damage concentrations. However, in a separate series of experiments with 500 keV Kr-ions, a release retarded with respect to volume diffusion of the gas was observed in Si and Ge.     

Concentration profiles during films deposition from a low-energy ion beam

An ion beam is described in the diffusion approximation, and a mathematical model of thin-film deposition process is developed. The volume profiles of concentration of components during nickel film deposition on a copper substrate are calculated for ion energies of 100, 200, and 400 eV and ion flux densities I = 10¹⁵, 10¹⁶, and 10¹⁷cm⁻²·s⁻¹. The deposition model parameters are estimated using programs SUSPRE and SRIM. The concentration profiles of the components are compared for the corresponding numerical values of the model parameters. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 27–34, March, 2007.     

Formation of small particles of gold on alumina support films and their behaviour in oxygen and hydrogen atmospheres

Attempt has been successfully made to disperse ultrafine gold particles on alumina support films by keeping the substrate at elevated temperatures during metal deposition under vacuum of ≈ 10^-5 Torr. It is found that reasonable dispersion of particles occurs for a mean thickness of 0.5 nm at a substrate temperature of 125 °C. The resulting samples turn out to be quite suitable for model studies of the behaviour of gold/alumina catalyst. Electron microscope observations coupled with diffraction have provided evidence for emergence of gold particles without any compound formation with the residual gases present during deposition at 10^-5 Torr. The nature of dispersion and average particle size are shown to depend on substrate temperature and the amount of metal evaporated. Heat treatments in hydrogen and oxygen at 200–500 °C for various lengths of time led to an increase in particle size with a simultaneous decrease in number density (i.e. coarsening of particles) following, in all probability, the Ostwald ripening mechanism. The oxidizing atmosphere has been shown to be more favourable to coarsening or deactivation of the catalyst. Finally, it is indicated that gold particles prefer to facet giving well-defined shapes (e.g. hexagonal, pentagonal or rhombohedral) with faces corresponding to planes of relatively smaller interfacial energies.     

Highly undersampled supraaortic MRA at 3.0 T: initial results with parallel imaging in two directions using a 16-channel neurovascular coil and parallel imaging factors up to 16

PurposeTo present the feasibility of highly undersampled contrast-enhanced MRA (CE-MRA) of the supraaortic arteries with a 16-channel neurovascular coil at 3.0 T using parallel imaging in two directions with parallel imaging factors (PIF) up to 16.Materials and MethodsInstitutional review board approval and informed consent were obtained. In a prospective study, MRA protocols including PIF of 1, 2, 4, 9 and 16 yielding a spatial resolution from 0.81×0.81×1.0 mm³ to 0.46×.46×0.98 mm³ were acquired. In 32 examinations, image quality and vascular segments were rated independently by two radiologists. SNR estimations were performed for all MRA protocols.ResultsThe use of high PIF allowed to shorten acquisition time from 2:09 min down to 1:13 min and to increase the anatomic coverage while maintaining or even increasing spatial resolution down to 0.46×0.46×0.98 mm³. The larger anatomic coverage that was achieved with the use of high PIF allowed for visualization of vascular structures that were not covered by the standard protocols. Despite the resulting lower SNR using high PIF, image quality was constantly rated to be adequate for diagnosis or better in all cases.ConclusionThe use of high PIF yielded diagnostic image quality and allowed to increase the anatomic coverage while maintaining or even improving spatial resolution and shortening the acquisition time.     

Theoretical study on the static and dynamic first-order hyperpolarisabilities of adenine tautomers

Static and dynamic electronic and vibrational first-order hyperpolarisabilities (β) of the lowest energy neutral adenine tautomers (amine forms A7 and A9) were obtained in gaseous and aqueous phases by using Hartree–Fock, Møller–Plesset second-order and fourth-order perturbation theory (MP2 and MP4-SDQ) and conventional and long-range corrected density functional theory methods with the Dunning's correlation-consistent cc-pVDZ, aug-cc-pVDZ, aug-cc-pVTZ and d-aug-cc-pVDZ basis sets. Frequency-dependent properties were calculated at the characteristic wavelength of the Nd:YAG laser (1064 nm) for the second harmonic generation and electro-optical Pockels effect nonlinear optical processes. Solvent effects were introduced under the polarised continuum model approximation. The electronic β^e values of the investigated isomers are noticeably affected by the theoretical level, basis set and solvation. In vacuum, the static and dynamic β^e values of A9 are greater than the corresponding data of A7, whereas the contribution of the solvent significantly enhances the hyperpolarisabilities of the A7 tautomer, resulting in β^e(A9)/β^e(A7) ratios between 0.5 and 0.6. The vibrational hyperpolarisabilities of the adenine tautomers are quite close to each other.