New developments in Raman spectroscopy

Summary A short review is given on some new instrumental and methodical developments in Raman spectroscopy. In linear Raman spectroscopy a microsampling technique, which is based on the optical levitation by radiation pressure, and the surface enhanced Raman effect (SERS) are discussed. In non-linear Raman spectroscopy new developments in coherent anti-Stokes Raman spectroscopy (CARS) and ionization detected stimulated Raman spectroscopy (IDSRS) as well as their applications in high resolution molecular spectroscopy and in combustion research are described.

---

Neuere Entwicklungen in der Raman-Spektroskopie

Zusammenfassung Es wird ein kurzer Überblick über einige neuere instrumentelle und methodische Entwicklungen in der Raman-Spektroskopie gegeben. In der linearen Raman-Spektroskopie wird eine Mikroprobentechnik, die auf der optischen Levitation durch Strahlungsdruck beruht, sowie der oberflächenverstärkte Ramaneffekt (SERS) diskutiert. Weiterhin werden neuere Entwicklungen nichtlinearer Ramanmethoden, wie CARS (Coherent anti-Stokes Raman Spectroscopy) and IDSRS (Ionization Detected Stimulated Raman Spectroscopy) sowie deren Anwendungen in der hochauflösenden Molekülspektroskopie und in der Erforschung von Verbrennungsvorgängen besprochen.

     

Fourier transform microwave and millimeter wave spectroscopy of quinazoline, quinoxaline, and phthalazine

The pure rotational spectra of the bicyclic aromatic nitrogen heterocycle molecules, quinazoline, quinoxaline, and phthalazine, have been recorded and assigned in the region 13-87 GHz. An analysis, guided by ab initio molecular orbital predictions, of frequency-scanned Stark modulated, jet-cooled millimeter wave absorption spectra (48-87 GHz) yielded a preliminary set of rotational and centrifugal distortion constants. Subsequent spectral analysis at higher resolution was carried out with Fourier transform microwave (FT-MW) spectroscopy (13-18 GHz) of a supersonic rotationally cold molecular beam. The high spectral resolution of the FT-MW instrument provided an improved set of rotational and centrifugal distortion constants together with nitrogen quadrupole coupling constants for all three species. Density functional theory calculations at the B3LYP∕6-311+G?? level of theory closely predict rotational constants and are useful in predicting quadrupole coupling constants and dipole moments for such species.     

Liquid crystal birefringence for millimeter wave radar

Abstract

Many liquid crystals are found to have relatively high birefringence (Δn) values in the microwave and millimeter wave regions, as calculated from the phase shift induced by their reorientation by magnetic or electric fields. At 30 GHz, Δn values were obtained in the range of 0.08 to 0.18 for eleven liquid crystal mixtures of various types. The most favourable liquid crystal structures for high millimeter wave birefringence are highly conjugated rod-like molecules containing biphenyl, terphenyl, phenylpyrimidine, biphenylpyrimidine, and tolane groups in nematics of positive dielectric anisotropy (Δε). However, other liquid crystal structures including Schiffs base, azoxybenzene, and aromatic ester groups also have substantial birefringence, including nematics with negative and crossover Δε, as well as cholesteric nematics. The Δn varied only slightly at different frequencies of microwave millimeter wave in the 15–94 GHz range. Studies on magnetic and electrical field liquid crystal orientation in specially designed waveguides provide a basis for new types of modulators and scanning array antennae in the millimeter wave region, where more compact liquid crystal modulation media can be used than in the microwave region. These scanners can be used for both sending and receiving radar signals for potentially low cost radar systems.     

The millimeter wave spectrum of iodoethyne,HCCI

The rotational spectrum of iodoethyne, HCCI, has been observed in the frequency range from 105 to 305 GHz. A sensitive spectrometer system employing source modulation, a harmonic generator millimeter wave source and a liquid helium cooled InSb-detector has been used. The rotational constants and nuclear quadrupole coupling parameters of HCCI have been obtained for the ground state and the first and second excited vibrational states of ν₄. The rotational spectrum of the 2ν₅ state has also been identified. The very weak spectrum shows unusual relative intensities which are interpreted by assuming a dipole moment change with ν₄ excitation of 0.07 D. The ground state dipole moment is then estimated to be 0.020(10) D.     

Study of intermolecular interactions in aqueous solutions by millimeter spectroscopy

The absorption of millimeter electromagnetic radiation (v=1.4, 1.71, and 5 cm⁻¹) by aqueous solutions of glycine (pH 6.1–6.2) in the concentration range of 0.5–2.5 mol L⁻¹ was measured. It was found that the absorbing ability of the water present in the solutions, is higher than that of pure water. This phenomenon is explained by the presence of a center of negative hydration in the structure of the glycine zwitterion, which results in an increase in the rotational mobility of water molecules immobilized in the hydrate shell of the glycine zwitterion. For Part 5, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1305–1307, July, 1997.     

Some recent developments in pressure tuning spectroscopy

Pressure tuning spectroscopy has proved to be a powerful tool for studying a wide variety of electronic phenomena. In this review we present two recent examples of the application of high pressure luminescence: (1) a test of the validity of a kinetic model for the emission characteristics of molecules that emit from excited states with different degrees of charge transfer and different geometries (molecules with twisted intramolecular charge transfer (TICT)); (2) an elucidation of the mechanism for the large difference observed between the luminescence efficiencies of [Ru(bpy)₃]²⁺ and [Ru(bpy)₂(py)₂]²⁺ in solid media.In 1994, Prof. H. G. Drickamer was awarded theHonoris causa degree by the Russian Academy of Sciences.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1195–1202, July, 1995.     

New developments in biosensors

Analytical and Bioanalytical Chemistry -     

New developments in catalysis

Environmental, safety and health concerns are major driving forces for the development of new coating systems, which in turn require catalysts with a different performance profile. One critical area for the development of new catalysts is the replacement of organotin compounds in polyurethanes with environmentally friendly catalysts, such as bismuth, aluminum and zirconium chelates. For applications in epoxies new catalysts for the epoxy-carboxyl reaction are also being developed. To gain the needed improved performance multiple cure mechanisms are being employed in coatings requiring dual action catalysts.     

Diffuse reflectance spectroscopy—Important developments

Effect of front surface reflectance is incorporated into standard Kubelka-Munk theory of diffuse reflection. A method of obtaining the absorption coefficient independent of scattering coefficient is presented.     

High-resolution millimeter wave spectroscopy and multichannel quantum defect theory of the hyperfine structure in high Rydberg states of molecular hydrogen H2

Experimental and theoretical methodologies have been developed to determine the hyperfine structure of molecular ions from detailed studies of the Rydberg spectrum and have been tested on molecular hydrogen. The hyperfine structure in l=0-3 Rydberg states of H2 located below the X 2Sigmag+(v+=0,N+=1) ground state of ortho H2+ has been measured in the range of principal quantum number n=50-65 at sub-MHz resolution by millimeter wave spectroscopy following laser excitation to np and nd Rydberg states using a variety of single-photon and multiphoton excitation sequences. The np1(1), nd1(1), and the nf1(0-3) Rydberg states were found to be metastable and to have lifetimes of more than 5 micros beyond n=50. Members of other series, such as the nd1(2), nd1(3), and the np1(0) series, were found to have lifetimes of more than 1 mus. Local perturbations induced by low-n Rydberg states belonging to series converging on rovibrationally excited levels of H2+ reduce the lifetimes in narrow ranges of n values. The hyperfine structure is strongly dependent on the value of the orbital angular momentum l. In the penetrating s and p states at n approximately 50 the exchange interaction dominates over the hyperfine interaction and the levels can be labeled by the total electron spin angular momentum quantum number S (S=0 or 1). In the less penetrating d and f Rydberg states, the hyperfine interaction between the core nuclear and electron spins is larger than the exchange interaction and the Rydberg states are of mixed singlet and triplet character. A procedure based on the Stark effect and on the systematic analysis of selection rules and combination differences was developed to determine the orbital and the total angular momentum quantum numbers l and F and to construct an energy map of p and f Rydberg levels between n=54 and 64 with relative positions of an accuracy of better than 1 MHz. Multichannel quantum defect theory (MQDT) was extended to treat the hyperfine structure in molecular Rydberg states and was used to analyze the observed hyperfine structure of the p and f Rydberg states of H2. The frame transformation between the Born-Oppenheimer channels described by the angular momentum coupling scheme (abetaJ) and the asymptotic channels described by the (e[bbetaS+]) coupling scheme was derived and enables an elegant treatment of all intermediate coupling cases. Purely ab initio quantum defect theory reproduced the experimentally determined positions to within 40 MHz for the p levels and 13 MHz for the f levels. By slight adjustments of the quantum defect functions and their energy dependences and by consideration of the p-f interaction, of the singlet-triplet splittings of the f levels, and of the departure of the ionic levels from pure coupling case (bbetaS+), the agreement between theory and experiment could be improved to 600 kHz. By comparing the results of MQDT calculations of the hyperfine structure of f Rydberg levels with those of coupled equations calculations, the frame transformation approximation of MQDT was shown to be accurate to within 300 kHz. The extrapolated ionic hyperfine structure of the X 2Sigmag+(v+=0,N+=1) ionic level corresponds to the ab initio prediciton of Babb and Dalgarno [Phys. Rev. A 46, R5317 (1992)] within the experimental error.     

Recent developments in the molecular spectroscopy of polymers

Summary There have recently been important advances in instrumentation in a number of forms of molecular spectroscopy. It is the purpose of this paper to show how these may be applied to extend our knowledge of synthetic polymers, with particular emphasis on analytical applications. Raman, nmr, and infra-red spectroscopy are dealt with.

---

Neuere Entwicklungen bei der Molekularspektroskopie von Polymeren

Zusammenfassung Die Fortschritte auf dem Gebiet der Molekularspektroskopie werden diskutiert, speziell die Anwendung zur Analyse von Polymeren. Raman-, KMR- und Infrarotspektroskopie werden behandelt.

Lecture presented at Euroanalysis I Conference, 28. 8. –1.9. 1972 in Heidelberg, Germany.     

New developments in photochromic polymers

New developments on photochromic polymers have been obtained with systems containing spirobenzopyran derivatives. The importance of the chemical incorporation of the photochrome within the polymer backbone is stressed, and the influence of matrix orientation on the rate of fading is shown. Well known fatigue phenomena are illustrated on the basis of the changes of photostationary optical density on repeating the irradiation–dark recovery cycle. The photomechanical properties and characteristics of rubbery polyethylacrylates crosslinked with the photochrome bismethacrylate are considered in detail. Another principle of photochromism based on photodissociation phenomena is also discussed in the case of the photodissociation and photorecombination of anthracene derivatives and benzacridizinium tosylate, as well as in the case of the photodissociation and thermal recombination of benzpinacol groups incorporated in the polymer main chain. In these experiments in the solid state, it can be shown that the recombination involves always two successive steps: a rapid step corresponding to cage recombination and a second slow step related to diffusion and segment mobility (T_g) of the polymer.     

New developments in clinical analysis

Summary The revolutionary development of clinical chemistry finds expression in the fact, that the total number of analyses doubles nearly every five years. The only solution of this problem is automation. Some examples of new developments in the fields of enzyme, protein and amino-acid chemistry are given. These few examples can be extended almost ad infinitum. It is clear however, that analytical chemical technique development goes hand in hand with modern instrumentation development. A short survey of some of the major points concerning spectrophotometry, gas chromatography and radioactive isotopes is given. Attention is finally drawn to a very important aspect of these new developments, which may easily be overlooked, namely standardization. A survey is given of the Dutch work on the standardization of haemoglobinometry (HiCN-method).

---

Zusammenfassung Die revolutionäre Entwicklung der klinischen Chemie wird schon dadurch klar ersichtlich, daß die Gesamtzahl der klinisch-chemischen Bestimmungen sich fast alle fünf Jahre auf das Zweifache steigert. Die einzige Lösung dieses Problems liegt in der Automatisierung. Einige Beispiele neuer Entwicklungen werden gegeben auf dem Gebiet der Enzym-, Eiweiß- und Aminosäurechemie. Diese wenigen Beispiele können ad infinitum ergänzt werden. Es ist jedoch klar, daß die Fortschritte in der analytischen Chemie unlöslich mit der Entwicklung neuer Apparaturen verbunden sind. Eine kurze Zusammenfassung dieser Entwicklung auf dem Gebiete der Spektrophotometrie, der Gaschromatographie und der radioaktiven Isotopenanalyse im klinisch-chemischen Laboratorium wird gegeben.Zum Schluß wird der Standardisierung klinisch-chemischer Bestimmungen Aufmerksamkeit gewidmet. Die Standardisierung nimmt im Rahmen der neuesten Entwicklungen eine hervorragende Stelle ein. Eine Übersicht der niederländischen Arbeit über die Standardisierung der Hämoglobinometrie, (HiCN-Methode), wird gegeben.

     

New developments in hyperbranched polymers

In the last 12 years the field of hyperbranched polymers has been well established with a large variety of synthetic approaches and fundamental studies on structure and properties of these unique materials. However, new developments involving hyperbranched materials appeared recently, for example, different synthetic strategies, new reaction mechanisms, formation of more complex architectures, a deeper understanding of the branched structure and their kinetic development, and intensive studies on the material properties and possible applications. This demonstrates the high versatility and the possibilities that are still involved in hyperbranched polymers and render it one of the most active fields in polymer science with a very promising future. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2505–2525, 2000     

Recent developments in the analytical application of UV-photoelectron spectroscopy

Summary Preliminary results from a number of new developments designed to make UV photoelectron spectroscopy analytically advantageous are reported. A versatile photoelectron spectrometer with a simple sample inlet system has been constructed. This has been successfully linked to a G.L.C. and in this combination serves either to provide a spectrum of the sample or acts as a selective G.C. detector. Data processing has been improved with the aid of a computer programme, which enables the spectrum of a mixture to be resolved into its components.

---

Neuere Entwicklungen bei der analytischen Anwendung der U V-Photoelektronen-Spektroskopie

Zusammenfassung Ein vielseitiges Photoelektronenspektrometer mit einfachem Probeneinlaßsystem wird beschrieben. In der Kombination mit einem Gas-Chromatographen kann entweder ein Spektrum der Probe geliefert werden oder das Gerät dient als selektiver GC-Detektor. Die Datenverarbeitung wurde mit Hilfe eines Computerprogramms verbessert, das es ermöglicht, das Spektrum eines Gemisches in seine Bestandteile aufzulösen.

Lecture presented at Euroanalysis I Conference, 28. 8. –1. 9. 1972 in Heidelberg, Germany.     

Early events and some later developments in microwave spectroscopy

The early history of microwave spectroscopy is reviewed. New directions in the field are indicated. These include: further extensions of coherent submillimeter wave spectroscopy, microwave spectroscopy of molecules in interstellar space, microwave-infrared laser double resonance, spectroscopy of ionized molecules and transient molecular radicals, studies of hydrogen-bonded molecular complexes and atom-molecule complexes, observations of “forbidden” rotational transitions in symmetric-top and spherical-top molecules, and new developments in high-temperature spectroscopy.     

Recent developments in two-dimensional (2D) correlation spectroscopy

Recent noteworthy developments in the field of two-dimensional(2D) correlation spectroscopy are reviewed.2D correlation spectroscopy has become a very popular tool due to its versatility and relative ease of use.The technique utilizes a spectroscopic or other analytical probe from a number of selections for a broad range of sample systems by employing different types of external perturbations to induce systematic variations in intensities of spectra.Such spectral intensity variations are then converted into2 D spectra by a form of correlation analysis for subsequent interpretation.Many different types of 2D correlation approaches have been proposed.In particular,2D hetero-correlation and multiple perturbation correlation analyses,including orthogonal sample design scheme,are discussed in this review.Additional references to other important developments in the field of 2D correlation spectroscopy,such as projection correlation and codistribution analysis,were also provided.