OH Stretch Absorption Research Articles

Spectroscopy and SEM imaging reveal endosymbiont-dependent components changes in germinating kernel through direct and indirect coleorhiza-fungus interactions under stress

In the present study, FTIR spectroscopy and hyperspectral imaging was introduced as a non-destructive, sensitive-reliable tool for assessing the tripartite kernel-fungal endophyte environment interaction. Composition of coleorhizae of Triticum durum was studied under ambient and drought stress conditions. The OH-stretch IR absorption spectrum suggests that the water-deficit was possibly improved or moderated by kernel’s endophytic partner. The OH-stretch frequency pattern coincides with other (growth and stress) related molecular changes. Analysis of lipid (3100–2800 cm−1) and protein (1700–1550 cm−1) regions seems to demonstrate that drought has a positive impact on lipids. The fungal endosymbiont direct contact with kernel during germination had highest effect on both lipid and protein (Amide I and II) groups, indicating an increased stress resistance in inoculated kernel. Compared to the indirect kernel-fungus interaction and to non-treated kernels (control), direct interaction produced highest effect on lipids. Among treatments, the fingerprint region (1800–800 cm−1) and SEM images indicated an important shift in glucose oligosaccharides, possibly linked to coleorhiza-polymer layer disappearance. Acquired differentiation in coleorhiza composition of T. durum, between ambient and drought conditions, suggests that FTIR spectroscopy could be a promising tool for studying endosymbiont-plant interactions within a changing environment.

Porosity effects on crystallization kinetics of amorphous solid water: Implications for cold icy objects in the outer solar system

We have investigated the effects of porosity on the crystallization kinetics of amorphous solid water (ASW). Porosity in ASW films, condensed from the vapor phase at varying incidences at 10K, was characterized using ultraviolet-visible interferometry and quartz crystal microgravimetry. The films were heated to crystallization temperatures between 130 and 141K, resulting in partial pore compaction. The isothermal phase transformation was characterized using transmission infrared spectroscopy to monitor the time evolution of the 3.1-µm OH stretch absorption band. We find that ASW crystallization unfolds in two distinct stages. The first stage, responsible for ∼10% transformation, is initiated from nucleation at the external surface. The dominant second stage begins with nucleation at the internal pore surfaces and completes the transformation of the film at a faster rate compared to the first stage. A key finding is that porosity has major influence on crystallization kinetics; a film with five-times-higher porosity was observed to crystallize ∼15 times faster, compared to the less porous counterpart. We extrapolate our results to predict crystallization times for amorphous ices condensed on Europa's surface from plume sources, as recently observed by the Hubble Space Telescope.

Distribution of phyllosilicates on the surface of Ceres.

The dwarf planet Ceres is known to host phyllosilicate minerals at its surface, but their distribution and origin have not previously been determined. We used the spectrometer onboard the Dawn spacecraft to map their spatial distribution on the basis of diagnostic absorption features in the visible and near-infrared spectral range (0.25 to 5.0 micrometers). We found that magnesium- and ammonium-bearing minerals are ubiquitous across the surface. Variations in the strength of the absorption features are spatially correlated and indicate considerable variability in the relative abundance of the phyllosilicates, although their composition is fairly uniform. These data, along with the distinctive spectral properties of Ceres relative to other asteroids and carbonaceous meteorites, indicate that the phyllosilicates were formed endogenously by a globally widespread and extensive alteration process.

Determination of Spectroscopic Band Shapes by Second Derivatives, Part II: Infrared Spectra of Liquid Light and Heavy Water.

Second derivative and band simulation techniques are used in a synergetic relationship to identify components in the infrared (IR) spectra of liquid light and heavy water. Nine Gaussian components are retrieved in massive OH and OD stretch absorption. In this context, ν1 and ν3 are the principal components along with satellites derived from harmonic and combination bands. The Raman spectrum of light water matches the IR components with intensity variations as expected.

Synthesis of 8-Methoxyquinoline-5-Amino Acetic Acid and its Herbicidal Potential

The quinoline skeleton is often used for the design of many synthetic compounds with diverse pharmacological properties. 8-Methoxyquinoline 5-amino acetic acid was synthesized from coupling of monochloroacetic acid with 5-amino-8-methoxyquinoline. The IR showed – OH stretch absorption and amino group (-NH) which is not too prominent at 3450cm-1 and 3300cm-1, carbonyl (C=O) absorption depicts at 1614cm-1. The herbicidal activity of the synthesized compound was tested on the weeds and after 11 days of application, the weeds have dried completely indicating the efficacy of the compound.

Size-resolved infrared spectroscopic study of structural transitions in sodium-doped (H₂O)n clusters containing 10-100 water molecules.

In water clusters containing 10-100 water molecules the structural transition takes place between "all surface" structures without internally solvated water molecules to amorphous water clusters with a three dimensionally structured interior. This structural evolution is explored with rigorous size selection by IR excitation modulated photoionization spectroscopy of sodium-doped (H2O)n clusters. The emergence of fully coordinated interior water molecules is observed by an increased relative absorption from 3200 to 3400 cm(-1) in agreement with theoretical predictions and earlier experimental studies. The analysis has also shown that the intermediate-sized water clusters (n = 40-65) do not smoothly link the structures in the largest and smallest analyzed size regions (n = 15-35 and n = 100-150) in line with previous reports suggesting the appearance of exceptionally stable water cluster isomers at n = 51, 53, 55, and 57. In the size range from n = 49 to n = 55 a reduced ion yield, a plateau in the total IR signal gain and signatures in the distribution of free OH stretch oscillator absorption have been observed. Recently reported putative global minima structures for n = 51 and n = 54 point to the presence of periplanar interior rings in odd-numbered clusters in this size range, which may affect cluster (surface) stability and the shape of the free OH stretch absorption peak. Potential links between pure and sodium-doped water cluster structures and the signatures of solvated electrons in photoelectron spectra of anionic water clusters are discussed.

Infrared detection of (H2O)20 isomers of exceptional stability: a drop-like and a face-sharing pentagonal prism cluster.

Water clusters with internally solvated water molecules are widespread models that mimic the local environment of the condensed phase. The appearance of stable (H2O)n cluster isomers having a fully coordinated interior molecule has been theoretically predicted to occur around the n = 20 size range. However, our current knowledge about the size regime in which those structures become energetically more stable has remained hypothetical from simulations in lieu of the absence of precisely size-resolved experimental measurements. Here we report size and isomer selective infrared (IR) spectra of (H2O)20 clusters tagged with a sodium atom by employing IR excitation modulated photoionization spectroscopy. The observed absorption patterns in the OH stretching region are consistent with the theoretically predicted spectra of two structurally distinct isomers of exceptional stability: a drop-like cluster with a fully coordinated (interior) water molecule and an edge-sharing pentagonal prism cluster in which all atoms are on the surface. The drop-like structure is the first experimentally detected water cluster exhibiting the local connectivity found in liquid water.

Water ice nanoparticles: size and temperature effects on the mid-infrared spectrum

Mid-infrared spectra have been measured for cubic ice (I(c)) nanoparticles (3-150 nm diameter) formed by rapid collisional cooling over a wide range of temperatures (5-209 K). Spectral diagnostics, such as the ratio of surface related dangling OH to interior H-bonded OH stretch bands, reveal the manner in which particle size depends on bath gas temperature and density, and on water molecule concentration. For particles smaller than 5 nm strained intermolecular bonds on the surface and subsurface cause the predominant OH stretch peak position to be dramatically blue shifted by up to 40 cm(-1). In the size regime of 8-200 nm the position of the OH stretch absorption band maximum is relatively unaffected by particle size and it is possible to measure the temperature dependence of the peak location without influences from the surface or scattering. The band maximum shifts in a linear fashion from 3218 cm(-1) at 30 K to 3253 cm(-1) at 209 K, which may assist with temperature profiling of ice particles in atmospheric clouds and extraterrestrial systems. Over the same temperature range the librational mode band shifts very little, from 870 to 860 cm(-1). In the water stretching and bending regions discrete spectral features associated with the surface or sub-surface layers have been detected in particles as large as 80 nm.

Hydrogen Bonding and OH-Stretch Spectroscopy in Water: Hexamer (Cage), Liquid Surface, Liquid, and Ice.

We present a unified picture of how OH-stretch spectroscopy in water can be understood in terms of hydrogen bonding for the four systems listed in the title. To understand the strength, and hence OH-stretch frequency, of a hydrogen bond, it is crucial to consider the number of additional acceptor hydrogen bonds made by both the donor and acceptor molecules. This necessity for focusing on the hydrogen-bond environment of both donor and acceptor molecules follows from quantum chemical considerations and is related to the three-body interactions in water. Armed with this understanding we can make a detailed interpretation of the OH-stretch IR absorption spectrum of the cage conformer for HOD(D2O)5 and the imaginary part of the ssp OH-stretch sum-frequency spectrum of the surface of liquid D2O with dilute HOD.

Finite element simulation of infrared laser ablation for mass spectrometry

Laser ablation is widely used in conjunction with ambient ionization techniques, and a fundamental understanding of the mechanism of material removal is important to its optimal use in mass spectrometry. Finite element analysis simulates the laser material interaction on larger time and distance scales than atomistic approaches. Here, a two-dimensional finite element model was developed to simulate infrared laser irradiation of glycerol using a wavelength-tunable infrared (IR) laser. The laser fluence used for the simulations was varied from 1000 to 6000 J/m(2), the wavelength was varied from 2.7 to 3.7 µm, and both flat-top and Gaussian shape laser profiles were studied. Phase explosion conditions were found for laser wavelengths near 3 µm (which corresponds to the OH stretch absorption of glycerol) and fluences above 2000 J/m(2). This suggests that laser ablation of glycerol is driven by phase explosion in the OH stretch region. The Gaussian profile generated regions of higher glycerol temperature, whereas the flat-top profile heated a larger volume of material above the phase explosion temperature. These results suggest that the best performance for pulsed IR laser sample irradiation is in the wavelength range from 2.9 to 3.1 µm for materials with a strong OH stretch absorption.

Kinetics of n-Butoxy and 2-Pentoxy Isomerization and Detection of Primary Products by Infrared Cavity Ringdown Spectroscopy

The primary products of n-butoxy and 2-pentoxy isomerization in the presence and absence of O(2) have been detected using pulsed laser photolysis-cavity ringdown spectroscopy (PLP-CRDS). Alkoxy radicals n-butoxy and 2-pentoxy were generated by photolysis of alkyl nitrite precursors (n-butyl nitrite or 2-pentyl nitrite, respectively), and the isomerization products with and without O(2) were detected by infrared cavity ringdown spectroscopy 20 μs after the photolysis. We report the mid-IR OH stretch (ν(1)) absorption spectra for δ-HO-1-C(4)H(8)•, δ-HO-1-C(4)H(8)OO•, δ-HO-1-C(5)H(10)•, and δ-HO-1-C(5)H(10)OO•. The observed ν(1) bands are similar in position and shape to the related alcohols (n-butanol and 2-pentanol), although the HOROO• absorption is slightly stronger than the HOR• absorption. We determined the rate of isomerization relative to reaction with O(2) for the n-butoxy and 2-pentoxy radicals by measuring the relative ν(1) absorbance of HOROO• as a function of [O(2)]. At 295 K and 670 Torr of N(2) or N(2)/O(2), we found rate constant ratios of k(isom)/k(O(2)) = 1.7 (±0.1) × 10(19) cm(-3) for n-butoxy and k(isom)/k(O(2)) = 3.4(±0.4) × 10(19) cm(-3) for 2-pentoxy (2σ uncertainty). Using currently known rate constants k(O(2)), we estimate isomerization rates of k(isom) = 2.4 (±1.2) × 10(5) s(-1) and k(isom) ≈ 3 × 10(5) s(-1) for n-butoxy and 2-pentoxy radicals, respectively, where the uncertainties are primarily due to uncertainties in k(O(2)). Because isomerization is predicted to be in the high pressure limit at 670 Torr, these relative rates are expected to be the same at atmospheric pressure. Our results include corrections for prompt isomerization of hot nascent alkoxy radicals as well as reaction with background NO and unimolecular alkoxy decomposition. We estimate prompt isomerization yields under our conditions of 4 ± 2% and 5 ± 2% for n-butoxy and 2-pentoxy formed from photolysis of the alkyl nitrites at 351 nm. Our measured relative rate values are in good agreement with and more precise than previous end-product analysis studies conducted on the n-butoxy and 2-pentoxy systems. We show that reactions typically neglected in the analysis of alkoxy relative kinetics (decomposition, recombination with NO, and prompt isomerization) may need to be included to obtain accurate values of k(isom)/k(O(2)).

Isotope effects in liquid water by infrared spectroscopy. V. A sea of OH4 of C2v symmetry

The two water gas OH stretch vibrations that absorb in the infrared (IR) near 3700 cm(-1) are redshifted to near 3300 cm(-1) upon liquefaction. The bathochromic shift is due to the formation of four H-bonds: two are from the labile hydrogen atoms to neighbors and two are received from neighbors by the oxygen free electron pairs. Therefore, the water oxygen atom is surrounded by four hydrogen atoms, two of these make covalent bonds that make H-bonds and two are oxygen H-bonded. However, these permute at rate in the ps range. When the water molecules are isolated in acetonitrile (MeCN) or acetone (Me(2)CO), only the labile hydrogen atoms make H-bonds with the solvent. The bathochromic shift of the OH stretch bands is then almost 130 cm(-1) with, however, the asymmetric (ν(3)) and symmetric (ν(1)) stretch bands maintained. When more water is added to the solutions, the oxygen lone doublets make H-bonds with the available labile hydrogen atoms from neighboring water molecules. With one bond accepted, the bathochromic shift is further displaced by almost 170 cm(-1). When the second oxygen doublet is filled, another bathochromic shift by almost 100 cm(-1) is observed. The total bathochromic shift is near 400 cm(-1) with a full width at half height of near 400 cm(1). This is the case of pure liquid water. Notwithstanding the shift and the band broadness, the ν(3) and ν(1) band individualities are maintained with, however, added satellite companions that come from the far IR (FIR) absorption. These added to the fundamental bands are responsible for the band broadness and almost featureless shape of the massive OH stretch absorption of liquid water. Comparison of light and heavy water mixture spectra indicates that the OH and OD stretch regions show five different configurations: OH(4); OH(3)D; OH(2)D(2); OHD(3); and OD(4) [J. Chem. Phys. 116, 4626 (2002)]. The comparison of the OH bands of OH(4) with that of OHD(3) indicates that the main component in OHD(3) is ν(OH), whereas in OH(4) two main components are present: ν(3) and ν(1). Similar results are obtained for the OD bands of OD(4) and ODH(3). These results indicate that the C(2) (v) symmetry of H(2)O and D(2)O is preserved in the liquid and aqueous solutions whereas C(s) is that of HDO.

Wavelength and Time-Resolved Imaging of Material Ejection in Infrared Matrix-Assisted Laser Desorption

The dynamics of glycerol ablation at atmospheric pressure was studied using fast photography. A mid-infrared optical parametric oscillator was used to irradiate a droplet of glycerol at normal incidence. The wavelength of the infrared source was tunable and was varied between 2.7 and 3.5 microm for the studies. After an adjustable delay, an excimer pumped dye laser was used to illuminate the expanding plume, and the 90 degrees scattered light was imaged with a high-speed CMOS camera. The time delay between the IR and UV lasers was varied up to 1 ms with a particular emphasis in the early stages of plume evolution below 1 micros. The threshold fluence for plume formation varied between 1000 and 6000 J/m(2), and the minimum fluence corresponded to the OH stretch absorption of glycerol near 3.0 microm, which also corresponded to the greatest scattered light signal and duration of material emission. The velocity of the expanding plume was measured and ranged from >300 m/s near the OH stretch absorption to <100 m/s near the 3.4 microm CH stretch. Plume modeling calculations suggest that material removal is driven by phase explosion in the stress confinement regime that is at a maximum near the wavelength of the OH stretch absorption.

Infrared spectroscopy of methanol-hexane liquid mixtures. I. Free OH present in minute quantities

Methanol and hexane mixtures covering the whole solubility range are studied by Fourier transform infrared attenuated total reflectance spectroscopy in order to evaluate OH groups that are H-bond-free. The mixtures from 0 to 0.25 and from 0.75 to 1.00 mole fractions form homogeneous solutions, whereas those from 0.25 to 0.75 mole fractions are inhomogeneous, forming two phases. Factor analysis (FA) was used to find out if free OH groups were present. These were found in minute quantities at the lowest mole fraction by evaluating the OH stretch absorption. The bulk of the absorption is due to the greater than 99.9% of hydrogen-bonded methanol molecules, with a band maximum situated at 3340 cm(-1). The stretch band of the free OH groups absorbs at 3654 cm(-1), with a full width at half maximum of 35 cm(-1). The concentration is very weak but constant at less than 5 mM in the mole fraction between 0.252 and 0.067. Below this range, OH concentrations are even smaller. This represents less than 1% of the amount of methanol at the mole fraction of 0.067 (0.543M). Above 0.25 mole fraction, free methanol OH groups are not observed. Since the free OH band is very weak, almost at the noise level, we verified its presence with mixtures of hexanol in hexane. There, we found a similar free OH band with almost the same band characteristics, but with almost three times the concentrations found with methanol, which we attribute to the difference in the hydrocarbon chain length. The present study indicates clearly that solutions of methanol in hexane contain free OH groups but in minute quantities and only in the low methanol concentrations. This situation is much different from that observed in solutions of methanol in CCl(4), where free OH groups are clearly observed at all concentrations except at the concentration limits. Whereas in CCl(4), methanol is believed to form H-bonded chains, the situation is different in n-hexane: methanol in the low concentration region would form reverse micelles with the OH groups in the core and the CH(3) groups mixed with n-hexane molecules.

Wavelength Dependence of Soft Infrared Laser Desorption and Ionization

Protonated insulin molecules were formed by soft IR laser desorption ionization of a thin film of the protein on a silicon surface. Time-of-flight mass spectra were recorded at wavelengths between 2.8 and 3.6 μm and the efficiency of ionization was compared to the IR absorption of the protein thin film. Ionization efficiency was quantified by recording the minimum laser energy per unit area required to produce a detectable ion signal (threshold fluence). The ionization efficiency tracks the IR absorption spectrum of insulin between 2.6 and 3.8 μm in the region of OH, NH, and CH stretch absorption. The lowest threshold fluence and therefore the most efficient ionization was nearly coincident with the OH stretch absorption of insulin near 3.0 μm. An additional local maximum in ionization efficiency was observed at 3.4 μm, coincident with the CH stretch vibrational absorption. Comparison of the ionization efficiency with the IR absorption indicates that the protein and not the residual solvent is absorbing the laser energy. Scanning electron microscopy images of the bovine insulin thin films on silicon after laser irradiation show melting and indications of explosive boiling. Ionization occurs through the sacrifice of some of the protein molecules that absorb the laser energy and act as an intrinsic matrix.

Surface‐Enhanced Vibrational Spectroscopy: SERS and SEIRA

AbstractWith respect to the origin of single‐molecule sensitivity in surface‐enhanced Raman scattering, elastic scattering and emission spectra were investigated for Ag particles adsorbed with dye. The scattering peak observed at 600–650 nm was extinguished during the inactivation process of an enormous SERS signal, whereas localized surface plasmon (LSP) peaks located at 520 nm and 730 nm did not change significantly. The scattering peak at 600–650 nm arises from increased electromagnetic coupling between the LSP of adjacent Ag particles through dye molecules. In addition, distinct emission peaks were observed at 550–600 nm and 600–750 nm for hot Ag particles with adsorbates. These bands were attributed to emissive relaxation of metal electrons and fluorescence of molecules, respectively. Furthermore, the shorter wavelength peak showed invariant Stokes shift irrespective of excitation wavelengths, most probably arising from inelastic scattering of excited electrons by adsorbed molecules.The adsorbed state of CO and related species on the Pt film electrode was investigated using attenuated total reflection—surface‐enhanced infrared absorption spectroscopy. Intermediate species were found on the bare Pt surface in 1 mM CH3OH + HClO4 solutions at +0.2 V ≤ E ≤ +0.6 V that give absorption peaks at 1405 cm−1 and 1300 cm−1. These bands can be attributed to carbonate species or ‐COH. Water molecules located at the hydrophobic interfaces between CO and electrolyte solutions were evidenced by a quite high OH stretch absorption at 3664–3646 cm−1, as well as a lower broad peak at ca. 3480 cm−1.

Spectroscopic Consequences of Localized Electronic Excitation in Anthranilic Acid Dimer

The electronic and infrared spectroscopy of anthranilic acid (o-aminobenzoic acid) dimer has been studied in a supersonic jet. Fluorescence-dip infrared (FDIR) spectra have been obtained in both the ground and first excited electronic states. The ground-state FDIR spectrum shows a broad, highly shifted OH stretch absorption commensurate with a cyclic, doubly hydrogen bonded structure, as has been observed for other carboxylic acid dimers. Density functional theory calculations predict that the dimer retains the monomer propensity for the amino group to be adjacent to the carbonyl group of the carboxylic acid, producing a C2h ground-state geometry for the dimer. The presence of the amino group shuts off the double proton tunneling that is present in benzoic acid dimer. The excited-state FDIR spectrum shows NH stretch fundamentals that are the sum of the S0 and S1 FDIR spectra of anthranilic acid monomer, indicating that the electronic excitation is localized on one of the monomers in the excited electronic state. The ultraviolet spectrum of the dimer shows a strong Franck−Condon progression involving a 58 cm-1 vibration and many combination bands with this mode. Comparison with density functional theory calculations indicates that the 58 cm-1 mode involves the in-plane geared bend of the two monomer units, which has bu symmetry in the C2h ground state. While this non totally symmetric fundamental appears in the R2PI and IR−UV hole-burning spectra, the dispersed fluorescence spectra from the S1 origin, +58 cm-1 band, and +118 cm-1 band display intensity only in even members of the 58 cm-1 progression. This Franck−Condon activity is quantitatively fit by a model in which the excited-state vibrations are simple sums and differences of localized, shifted harmonic oscillator vibrational wave functions, producing unresolved ag/bu tunneling doublets associated with the large barrier that separates the two minima on the excited-state surface.

Infrared spectroscopy of acetone-water liquid mixtures. II. Molecular model.

In aqueous acetone solutions, the strong bathochromic shifts observed on the OH and CO stretch infrared (IR) bands are due to hydrogen bonds between these groups. These shifts were evaluated by factor analysis (FA) that separated the band components from which five water and five acetone principal factors were retrieved [J. Chem. Phys. 119, 5632 (2003)]. However, these factors were abstract making them difficult to interpret. To render them real an organization model of molecules is here developed whose abundances are compared to the experimental ones. The model considers that the molecules are randomly organized limited by the hydrogen bond network formed between the water hydrogen atoms and the acetone or water oxygen atoms, indifferently. Because the oxygen of water has two covalent hydrogen atoms which are hydrogen-bonded and may receive up to two hydrogen atoms from neighbor molecules hydrogen-bonded to it, three types of water molecules are found: OH2, OH3, and OH4 (covalent and hydrogen bonds). In the OH stretch region these molecules generate three absorption regimes composed of nu3, nu1, and their satellites. The strength of the H-bond given increases with the number of H-bonds accepted by the oxygen atom of the water H-bond donor, producing nine water situations. Since FA cannot separate those species that evolve concomitantly the nine water situations are regrouped into five factors, the abundance of which compared exactly to that retrieved by FA. From the factors' real spectra the OH stretch absorption are simulated to, respectively, give for the nu3 and nu1 components the mean values for OH2, 3608, 3508; OH3, 3473, 3282 and OH4, 3391, 3223 cm(-1). The mean separations from the gas-phase position which are respectively about 150, 330, and 400 cm(-1) are related to the vacancy of the oxygen electron doublets: two, one, and zero, respectively. No acetone hydrate that sequesters water molecules is formed. Similarly, acetone produces ten species, two of which evolve concomitantly. Spectral similarities further reduce these to five principal IR factors, the abundance of which compared adequately to the experimental results obtained from FA. The band assignment of the five-acetone spectra is given.

Dynamics of water molecules in an alkaline environment

We report on a two-color mid-infrared pump–probe spectroscopic study of the dynamics of the OH stretch vibrations of HDO molecules dissolved in a concentrated (10 M) solution of NaOD in D2O. We observe that spectral holes can be created in the broad OH stretch absorption band that change neither position nor width on a picosecond time scale. This behavior differs strongly from that of pure HDO:D2O where rapid spectral diffusion (τc≈600 fs) occurs. The long-living inhomogeneity indicates that a concentrated aqueous NaOX (X=H,D) solution has a very static hydrogen-bond network. The results also show that the absorption band of the OH stretch vibration consists of two separate classes of OH groups with very different vibrational lifetimes. For component I, the lifetime of the OH stretch vibration is ∼600 fs and increases with OH frequency, which can be explained from the accompanying decrease in the strength of the hydrogen-bond interaction. This component represents HDO molecules of which the OH group is bonded to a D2O molecule via a DO–H⋯OD2 hydrogen bond. For component II, the lifetime is ∼160 fs, and does not show a significant frequency dependence. This component represents HDO molecules that are hydrogen bonded to a D2O molecule or an OD− ion. The short, frequency-independent vibrational lifetime of component II can be explained from the participation of the HDO molecule and its hydrogen-bonded partner in deuteron and/or proton-transfer processes.

Transmission near-field scanning microscope for infrared chemical imaging

We report transmission infrared near-field scanning microscopy (IR-NSOM) imaging of chemically amplified photoresist polymers patterned by ultraviolet exposure. Chemical specificity was attained using infrared wavelengths tuned to the 3 μm OH stretch absorption band of the polymer, a band sensitive to the chemical changes characteristic of the lithographic photochemical process of this material. Contrast mechanisms are discussed together with the IR-NSOM specifics, such as the fabrication of an infrared near-field probe with high throughput, which lead to an attainable resolution of λ/10 and a transmission sensitivity of 1%.