Vibrational Intensities. II. The Use of Isotopes

Crawford, Bryce

doi:10.1063/1.1700660

Cited by 298 publications

(47 citation statements)

References 6 publications

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“…The true relative accessibility might, however, differ from both results of the present study and theoretical estimations (electronic supplementary material) because of inherent problems with the spectroscopic method caused by dissimilar molar absorptivities of OH and OD stretching vibrations (Crawford 1952;Mann and Marrinan 1956b). For instance, the OD stretching vibrations in cellulose and starch were found to be about 10% more intense than OH stretching vibrations (Mann and Marrinan 1956b;Nara et al 1981) which would increase the spectroscopically determined accessibility.…”

Section: Hydroxyl Accessibility To Liquid D 2 Ocontrasting

confidence: 47%

“…For instance, the OD stretching vibrations in cellulose and starch were found to be about 10% more intense than OH stretching vibrations (Mann and Marrinan 1956b;Nara et al 1981) which would increase the spectroscopically determined accessibility. On the other hand, OD vibrations are theoretically expected to be less intense (Crawford 1952;Swenson 1965) Two further GREEN and GREENVAC sub-batches were never dried out between deuteration and reprotonated procedures, yet showed hydroxyl accessibilities in the range 0.4-1.2%. These results should be compared with the hydroxyl accessibility determined for never-deuterated controls yielding 0.7%, simply due to noise in the band region of the OD stretching vibration.…”

Section: Hydroxyl Accessibility To Liquid D 2 Omentioning

confidence: 99%

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Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

2017

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The first drying of wood cell walls from the native state has sometimes been described as producing irreversible structural changes which reduce the accessibility to water, a phenomenon often referred to as hornification. This study demonstrates that while changes do seem to take place, these are more complex than what has hitherto been described. The accessibility of wood cell wall hydroxyls to deuteration in the form of liquid water was not found to be affected by drying, since vacuum impregnation with liquid water restores the native cell wall accessibility. Contrary to this, hydroxyl accessibility to deuteration by water vapour was found to decrease to different levels depending on the drying conditions. Vacuum drying at 60°C for 3 days reduced the accessibility more than drying for 1 day at 103°C without vacuum. Drying for 3 days at 103°C increased the hydroxyl accessibility compared to 1 day. Moreover, the decrease in hydroxyl accessibility to deuteration by water vapour induced by the first drying could be at least partially erased by subsequent vacuum impregnation with liquid water, indicating reversibility. For the drying of solid, non-degraded wood cell walls the results challenge the often supposed process of hornification, understood as a permanent decrease in hydroxyl accessibility to water.

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Section: Hydroxyl Accessibility To Liquid D 2 Ocontrasting

confidence: 47%

Section: Hydroxyl Accessibility To Liquid D 2 Omentioning

confidence: 99%

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

2017

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“…This is not necessarily correct as O-D stretching vibrations in cellulose, starch, and wood have been reported to be about 10% more intense than O-H stretching vibrations (Mann and Marrinan 1956b;Nara et al 1981;Thybring et al 2017). From theoretical calculations, O-D stretching vibrations are expected to be less intense than O-H stretching vibrations (Crawford 1952;Swenson 1965), in line with studies on liquid normal and heavy water showing 29% lower intensity for O-D stretching vibrations (Venyaminov and Prendergast 1997). Moreover, it should be noted, as discussed for gravimetric techniques, that deuteration will not exchange hydrogens on all hydroxyls interacting with water as shown by Lindh et al (2016), only those capable of acting as hydrogen bond donor, i.e.…”

Section: Vibrational Spectroscopymentioning

confidence: 88%

Experimental techniques for characterising water in wood covering the range from dry to fully water-saturated

2017

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Water plays a central role in wood research, since it affects all material properties relevant to the performance of wood materials. Therefore, experimental techniques for characterising water within wood are an essential part of nearly all scientific investigations of wood materials. This review focuses on selected experimental techniques that can give deeper insights into various aspects of water in wood in the entire moisture domain from dry to fully water-saturated. These techniques fall into three broad categories: (1) gravimetric techniques that determine how much water is absorbed, (2) fibre saturation techniques that determine the amount of water within cell walls, and (3) spectroscopic techniques that provide insights into chemical wood-water interactions as well as yield information on water distribution in the macro-void wood structure. For all techniques, the general measurement concept is explained, its history in wood science as well as advantages and limitations.

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“…Theories of IR intensities [31][32][33][34] have evolved [23][24][25] to include contributions from two principal factors: dipole derivatives and proximity to electronic transitions. Substantial dipole derivatives arise when charge distributions evolve in response to vibrations 35,36 and these can become 'massive', for example, for charged solitons in polyacetylene 37,38 .…”

Section: Discussionmentioning

confidence: 99%

Giant infrared absorption bands of electrons and holes in conjugated molecules

et al. 2013

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Infrared (IR) absorption bands often convey identifying information about molecules, but are usually weak, having molar absorption coefficients o200 M À 1 cm À 1 . Here we report observation of radical anions and cations of conjugated oligomers and polymers of fluorene and thiophene that possess intense mid-infrared absorption coefficients as large as 50,000 M À 1 cm À 1 , perhaps the largest known for molecular species. For anions of fluorene oligomers, F n , n ¼ 2-4, IR intensities increase almost linearly with n, but with a slope much larger than one, indicating that the absorptions are not extensive properties. Large intensities seem to arise from a mechanism known for charged solitons and polarons in conjugated polymers. In this mechanism, vibrations of ungerade symmetry drive substantial displacements of charge, creating the large dipole derivatives responsible for intense IR absorption. Both experiments and calculations find that pairing with counter-ions attenuates IR band intensities. The IR bands may be diagnostic for bound ion pairs and their escape to form free ions.

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Vibrational Intensities. II. The Use of Isotopes

Cited by 298 publications

References 6 publications

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

Hydroxyl accessibility in wood cell walls as affected by drying and re-wetting procedures

Experimental techniques for characterising water in wood covering the range from dry to fully water-saturated

Giant infrared absorption bands of electrons and holes in conjugated molecules

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