The original work of Strobl and Hagedorn suggesting the presence of a third intermediate phase in semicrystalline polyethylene was revisited. The current study, involving the collection of Raman spectroscopic data on a set of 16 polyethylene samples recorded on two different types of instruments in two different laboratories and employing two different methods of curve fitting to both sets of experimental data, has revealed that the claims in the original paper cannot be asserted. The most important reason leading to this conclusion is a problem in correctly describing the complicated overlapping spectral structure in the 1000-1200 and 1400-1500 cm-l spectral ranges. It is noted that the contribution of the melt in the 1000-1150 cm-l range cannot be described by a single line centered around 1080 cm-l. The present results indicate that the quantification of a third, intermediate, phase in polyethylene is not possible when based on standard Raman spectra.

Confocal Raman microspectroscopy has previously used pinholes placed at the back focal plane of the microscope to provide depth resolution along the optical axis. The process of optimizing the pinhole alignment can often be difficult and time-consuming. We demonstrate a different approach to setting up a confocal Raman microscope using a stigmatic spectrograph and a CCD detector. This arrangement is easy to use and provides a depth resolution of ∼2 μm.

The p-benzosemiquinone and p,p'-biphenylsemiquinone free-radical anions have been produced by both chemical and photochemical methods. Resonance Raman spectra recorded from these free radicals are compared with those of the neutral parent compounds. The observed parent-to-radical Raman wavenumber shifts have been interpreted in terms of the structural changes that occur upon radical formation. Electronic absorption spectra of both radical species have been recorded and analysed. These have been used in conjunction with the resonance Raman data and excitation profiles to elucidate the excited-state geometries of the radicals. The resonance Raman spectrum of the p,p'-biphenylsemiquinone radical-anion dimer also is reported, as is its electronic absorption spectrum.