| 1. |
- Bai, Xiao, et al.
(author)
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Absorption of formaldehyde (H2CO) in the (A)over-tilde(1)A(2)
- 2004
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In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 60:4, s. 821-828
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Journal article (peer-reviewed)abstract
- The electronic A(1)A(2) <-- X(1)A(1) absorption spectra of formaldehyde vapour were studied at temperatures varying from 423 to 770 K with variable pressures from less than 0.1 to 1 MPa. Broadband vibronic and partially rotationally resolved 4(n)(1) rovibronic spectra of formaldehyde showed considerable sensitivity to temperature. The high resolution spectra showed collision-induced broadening as the pressure was increased. The results show that the absorption efficiency of the laser radiation front the third harmonic of Nd:YAG lasers is sensitive to the spectral properties of the laser, such as line position and shape. Promising results were obtained from the comparison between theoretical and measured absorption spectra.
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| 2. |
- Brackmann, Christian, et al.
(author)
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Laser-induced fluorescence of formaldehyde in combustion using third harmonic Nd : YAG laser excitation
- 2003
-
In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 59:14, s. 3347-3356
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Journal article (peer-reviewed)abstract
- Formaldehyde (CH2O) is an important intermediate species in combustion processes and it can through laser-induced fluorescence measurements be used for instantaneous flame front detection. The present study has focussed on the use of the third harmonic of a Nd:YAG laser at 355 nm as excitation wavelength for formaldehyde, and different dimethyl ether (C2H6O) flames were used as sources of formaldehyde in the experiments. The investigations included studies of the overlap between the laser profile and the absorption lines of formaldehyde, saturation effects and the potential occurrence of laser-induced photochemistry. The technique was applied for detection of formaldehyde in an internal combustion engine operated both as a spark ignition engine and as a homogenous charge compression ignition engine. (C) 2003 Elsevier B.V. All rights reserved.
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| 3. |
- Hammarstrom, L., et al.
(author)
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A biomimetic approach to artificial photosynthesis : Ru(II)-polypyridine photo-sensitisers linked to tyrosine and manganese electron donors
- 2001
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In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - 1386-1425 .- 1873-3557. ; 57:11, s. 2145-2160
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Research review (peer-reviewed)abstract
- The paper describes recent advances towards the construction of functional rr mics of the oxygen evolving complex in photosystem II (PSII) that are coupled to photoinduced charge separation. Some key principles of PSII and artificial systems for light-induced charge accumulation are discussed. Systems are described where biomimetic electron donors - manganese complexes and tyrosine - have been linked to a Ru(II)-polypyridine photosensitiser. Oxidation of the donors by intramolecular electron transfer from the photo-oxidised Ru(III) complex has been studied using optical flash photolysis and EPR experiments. A step-wise electron transfer Mn-2(III,III) --> tyrosine --> Ru(III) has been demonstrated, in analogy to the reaction on the donor side of PSII Electron transfer from the tyrosine to Ru(III) was coupled to tyrosine deprotonation. This resulted in a large reorganisation energy and thus a slow reaction rate, unless the tyrosine was hydrogen bonded or already deprotonated. A comparison with analogous reactions in PSH is made. Finally, light-induced oxidation of a manganese dimer linked to a Ru(II)-photosensitiser has been observed. Preliminary results suggest the possibility of photo-oxidising manganese dimers in several steps, which is an important advancement towards water oxidation.
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| 4. |
- Jensen, PS, et al.
(author)
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Determination of urea, glucose, and phosphate in dialysate with Fourier transform infrared spectroscopy
- 2004
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In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 60:4, s. 899-905
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Journal article (peer-reviewed)abstract
- Individual control and quantification of phosphate removal is desirable in dialysis treatment. Currently, no on-line method exists to quantify phosphate removal. We demonstrate that a multivariate calibration model based on infrared transmission spectra is capable of predicting phosphate, urea, and glucose concentrations at clinically relevant levels. The on-line monitoring of these components by infrared spectroscopy is therefore feasible. (C) 2003 Elsevier B.V. All rights reserved.
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| 5. |
- Metz, Thomas, et al.
(author)
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Fluorescence lifetimes of formaldehyde (H2CO) in the (A)over-tilde(1)A(2) -> (X)over-tilde(1)A(1) band system at elevated temperatures and pressures
- 2004
-
In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 60:5, s. 1043-1053
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Journal article (peer-reviewed)abstract
- Fluorescence lifetimes of formaldehyde excited by picosecond laser radiation with a wavelength of 355 nm were determined in nitrogen gas in a cell using time-resolved laser-induced fluorescence spectroscopy. The measurements were conducted at temperatures between 295 and 770 K and pressures up to 10 bar (1 MPa). Detection was broadband in most cases. Temperature and pressure were found to have a quenching effect on the fluorescence. At 295 K and pressures between 1 and 5 bar, decay rates between 0.03 and 0.04 ns(-1) were observed. At 770 K, the decay rates increased from 0.11 to 0.17 ns(-1) as the pressure was raised from 1 to 10 bar. The dependence on pressure was not linear at 1 bar. At 10 bar the linearity is unclear. The dependence on temperature appeared to be exponential. (C) 2003 Elsevier B.V. All rights reserved.
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| 6. |
- Mikulskiene, Birute, et al.
(author)
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On the stability of the hydrogen chloride complexes with ethylene and acetylene. A high resolution gas phase and ab initio study
- 2003
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In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 59:4, s. 733-741
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Journal article (peer-reviewed)abstract
- The temperature dependencies of the intensities of the HCl stretching bands of the hydrogen chloride complexes with acetylene and ethylene have been used to obtain estimates of the dissociation enthalpies of the two complexes. Quantum chemical calculations on the Hartree Fock and DFT/B3LYP levels of theory have been combined with experimental data to give estimates of the intensities of the HCl stretching vibration in the two complexes.
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| 7. |
- Nilsson, A. M. K., et al.
(author)
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Near infrared diffuse reflection and laser-induced fluorescence spectroscopy for myocardial tissue characterisation
- 1997
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In: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 53:11, s. 1901-1912
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Journal article (peer-reviewed)abstract
- In order to evaluate the potential of cardiovascular tissue characterisation using near-infrared (NIR) spectroscopy, spectra in a previously unexplored wavelength region 0.8-2.3 mu m were recorded from various pig heart tissue samples in vitro: normal myocardium (with and without endo/epicardium), aorta; fatty and fibrous heart tissue. The spectra were analysed with principal component analysis (PCA), revealing several spectroscopically characteristic features enabling tissue classification. Several of the identified spectral features could be attributed to specific tissue constituents by comparing the tissue signals with spectra obtained from water, elastin, collagen and cholesterol as well as with published data. The results obtained with the NIR spectroscopy technique in terms of its potential to classify different tissue types were compared with those from laser-induced fluorescence (LIF) using 337 nm excitation. LIF and NIR spectroscopy can in combination with PCA be used to discriminate between all previously mentioned tissue groups, apart from fatty versus fibrous tissue (LIF) and aorta versus fibrous tissue (NIR), respectively. The NIR analysis was improved by focusing the PCA to the wavelength segment 2.0-2.3 mu m, resulting in successful spectral characterisation of all cardiovascular tissue groups.
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| 8. |
- Holmgren, Allan, et al.
(author)
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Fourier transform infrared and Raman study of Alizarin Red S adsorbed at the fluorite-water interface
- 1999
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In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - 1386-1425 .- 1873-3557. ; 55:9, s. 1721-1730
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Journal article (peer-reviewed)abstract
- The adsorption of 1,2-dihydroxyanthraqinone-3-sulphonate (ARS) onto the surface of fluorite mineral was studied using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and Fourier transform (FT) Raman spectroscopy. The FT-Raman method proved to be more appropriate for this study when ARS was adsorbed from alkaline solution. At pH 6 both DRIFT and Raman spectra indicate non-precipitated ARS on the fluorite surface. At higher pH Raman spectra indicate ARS to be attached to the fluorite surface through the quinoid group at the 9-position and the α-phenolic oxygen.
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| 9. |
- Kalinin, Stanislav V., et al.
(author)
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Partial Donor-Donor Energy Migration (PDDEM) as a Fluorescence Spectroscopic Tool for Measuring Distances in Biomacromolecules
- 2002
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In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - 1386-1425 .- 1873-3557. ; 58:5, s. 1087-1097
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Journal article (peer-reviewed)abstract
- A theoretical model is presented, tested and applied for determining the rates of energy migration and distances within pairs of chemically identical fluorophores, so-called donors (D), which are exposed to different physical properties. The model is a general extension of the recently developed donor–donor energy migration (DDEM) model [J. Chem. Soc., Faraday Trans. 92 (1996)1563; J. Chem. Phys. 105 (1996) 10896] that applies to examining structure-function of biomacromolecules, such as proteins. Most fluorescent groups of the same kind incorporated at different positions (α and β) in a macromolecule exhibit shifts of the absorption and/or emission spectra, as well as different relaxation rates of the photophysics. As a consequence, the energy migration between the Dα and Dβ groups will be partially reversible. We refer to this case, as the partial donor–donor energy migration (PDDEM). The models of PPDEM presented can be used for analysing time-resolved fluorescence relaxation, as well as fluorescence depolarisation experiments. To explore the limitations of the PDDEM model, we have generated and re-analysed synthetic data that mimic time-correlated single photon counting (TCSPC) experiments. It was found that slow and fast rates of energy migration are most accurately recovered from the fluorescence relaxation and the depolarisation experiments, respectively. At comparable transfer and fluorescence rates, both kinds of experiments are equally useful. Real experiments on PDDEM were performed on an asymmetrically quenched bichromophoric molecule (1,32-dihydroxy-dotriacontane-bis-(Rhodamine 101) ester), that spans across the lipid bilayer of a vesicle. The depolarisation data were analysed by the PDDEM model and provide a distance between Rhodamine 101 groups, which agrees with independent studies
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| 10. |
- Kloo, Lars A., et al.
(author)
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Spectroscopic characterisation of indium(III) chloride and mixed ligand complexes
- 2002
-
In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - 1386-1425 .- 1873-3557. ; 58:5, s. 953-957
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Journal article (peer-reviewed)abstract
- Acidic solutions of InCl3 plus InBr3 contain mixed halide complexes and solvent extraction yields the four-coordinate anions InClnBr4-n- whose v(In-Cl) and v(In-Br) modes are reported. Two solid products of InCl3 with 15-crown-5 have been identified; crystallisation from aqueous HCl gave a molecular adduct containing InCl3(H2O)(2), whereas the ionic complex [InCl2(15-crown-5)][InCl4] was produced under anhydrous conditions. The vibrational spectra are assigned.
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