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A spin-flip Raman laser is fed simultaneously with two or more output frequencies of the CO pump laser. Not only are resonance effects seen when the magnetic field is tuned so that the Raman frequency equals the difference of two pump frequencies, but also when higher order resonances involving the sums and differences of CO lines equal the Raman frequency. The sign and intensity of these effects are briefly discussed and it is pointed out that the effects could be useful for calibration purposes.

Multiplicity of the output frequency of a spin-flip laser, caused by the simultaneous multiline operation of the CO pump laser, is identified. This multiplicity is shown to arise from a four-wave mixing process for which only a single input threshold intensity exists for oscillation. Experimental data are presented together with a determination of the interdependence of the input and output frequency power ratio.

Table 1 indicates the radicals proposed to interpret the electron spin resonance spectra of malonic acid and its ethyl, n-propyl and n-butyl derivatives irradiated with X-rays at 77°K. The new radicals formed and the radicals which disappear on warming to 195°K and finally to 300°K are also indicated.

The applications of electron spin resonacne to polymer studies are descussed in relation to the principles and the applications already made. Special attention is devoted to the counting of radicals during polymerisation and to the chemical identification of radical species by means of their hyperfine structure. Es wird die Anwendug von Elektronenspinresonanzmessungen auf das Studium von Polymeren im Hinblick auf die Grundlagen und die schon gemachen Anwendungen diskutiert. Die besondere Aufmerksamkeit wird dabei auf die Bestimmung der Radikale wahrend der Polymerisation und auf die chemische Identifizierung der Radikalarten mit Hilfe ihrer Hyperfeinstruktur gelenkt.

The electron spin resonance spectra of the radical CO2—CF2CFCO2— trapped in a single x‐irradiated crystal of sodium perfluorosuccinate hexahydrate were examined at both 9000 Mc/sec and 35 000 Mc/sec. The principal values of the hyperfine coupling tensor for the α fluorine are +421, +165, and +11 Mc/sec; for one of the β fluorine +176, +64, and +52 Mc/sec, and for the other β fluorine +200, +75, and +64 Mc/sec. These are briefly discussed in terms of the electronic structure and the values in chemically related radicals.

The extent of intramolecular hydrogen-bonding, as determined by infra-red spectroscopy in the hydroxyl stretching region, in certain vicinal diols of cyclo hexane, cyclo pentane, tetrahydropyran and tetrahydrofuran and in related compounds provides evidence for the stabilities of different conformations. In certain compounds these stabilities can be affected by hydrogen bonding from a substituent hydroxyl group to a ring oxygen. Additional evidence is provided in the case of the tetrahydropyran diols by [ M ] D values. The rate of reaction of the vicinal diols of these cyclic systems with glycol splitting reagents, and their zone electrophoretic mobility in an alkaline borate buffer is influenced by the presence of a ring oxygen.

Elelctron spin resonance measurements have been used to follow radical concentrations in the copolymerization of methyl methacrylate and glycol dimethacrylate at 23 and 0°C. and the decay of such radicals. The results have been interpreted to give a qualitative picture of the radical trapping process. It has also been shown that the allyl group in allyl methacrylate is comparatively unreactive and does not take much part in either the polymerization of this monomer or its copolymerization with glycol dimethacrylate. Acrylonitrile and α-methyl acrylonitrile have been shown to give different electron spin resonance spectra illustrating the effect of a chain methyl group. This parallels electron resonance studies of γ-irradiated acrylates and methacrylates.

It is shown that the relative signs of the hyperfine coupling constants of two spin ½ nuclei with isotropic coupling to one unpaired electron can be experimentally determined using the ENDOR technique with two radio-frequency fields in addition to the microwave field.

A theory is developed to predict the energy levels and transition intensities of the A proton in an AX-type high-resolution spectrum when a strong radiofrequency field is applied near the X proton resonance. The results are expressed in a graphical form that clearly illustrates the two possible methods of investigating the decoupled A resonance pattern, the `field sweep' and the `frequency sweep' methods. Experimental results for dichloroacetaldehyde show close agreement with these predictions for both methods of investigation. Instrumentation based on a suggestion of Primas (1961) has been used to maintain a very high degree of stability in the electromagnet field during the `frequency sweep' experiments.

The extent of intramolecular hydrogen bonding between hydroxyl groups and ring oxygens, as determined by infra-red spectroscopy in the hydroxyl stretching region, in a series of monohydroxy derivatives of tetrahydropyran, tetrahydrofuran and 1:3-dioxan provides direct experimental evidence for the stabilities of different conformations of certain of the alcohols. The synthesis of tetrahydropyran-3-ol is described and the mechanism of the reaction of perbenzoic acid with glycals is discussed.

In view of a recent paper ( 2 ) on the general features of anisotropic hyperfine coupling this written contribution is restricted to a discussion of the resonance parameters of XO 3 species with 25 valence electrons. These will exemplify the type of interpretation and show the changes to be expected from the variation of the position of X in the periodic table.

We report the first use of the spin-flip laser (SFL) for infrared photochemistry. The tuning capability combined with high intensity (up to 1W c.w. in a single mode) has been used to promote chemical reactions of molecules held in matrix isolation; these laser induced processes display not only isotopic and stereochemical selectivity but also selectivity between molecules in different sites in the matrix.

The method of electron spin resonance spectroscopy for studying free radicals and related materials is outlined and the basic parts of the theory are given. Some typical spectrometers are indicated and details are given of the arrangement of samples of different kinds. Three systems are discussed in some detail, as examples, namely the spectrum of a free radical in irradiated alanine, the semiquinone spectrum in solution and the haemoglobin crystal structure problem. Reference is made to applications in biology and related fields; subjects of special importance include radiobiology, photosynthesis, enzymic oxidation and nucleic acid complexes.

A description is given of a simple electronic stabilizer designed to supply an electromagnet with a current of 3 A, stable to one part in 3 × 104. Provision is made for the linear variation of this current with time.

IN a previous report1 we showed that the stretching frequency of the axial C1—D in the 1-deutero derivatives of β-D-glucose and β-D-mannose was about 40 cm.−1 lower than the corresponding equatorial C1—D in the 1-deutero derivatives of α-D-glucose and α-D-mannose. Examination of a further series of 1-deutero carbohydrate derivatives (see Table 1) has revealed that this is a general feature of hexo-pyranose derivatives and that the stretching frequencies of the equatorial C1—D groups of two crystalline D-pentopyranoses also fall in the same range as those of other equatorial groups. Although these stretching frequencies (some of which appear double) were measured with a sodium chloride prism and not therefore with great accuracy, the consistent differences were beyond experimental error and it was possible to resolve the frequencies of both anomers in the spectra of impure samples. The C—H stretching frequencies were not resolved by the infra-red spectrometer used in this work; the frequency of the approximate centre of the C—H stretching band was used in calculating the ratios recorded in Table 1.

Molecular Spectroscopy. By Ira N. Levine. Pp. x+491. (Wiley-Interscience: New York and London, June 1975.) £10.50. Organic Spectroscopy. (A Macmillan Chemistry Text.) By William Kemp. Pp. xvi + 248. (Macmillan: London and Basingstoke, June 1975.) £7.95 hard cover; £2.95 paper.