| 1. |
- Afzelius, Mikael, et al.
(författare)
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Dual-broadband rotational CARS modelling of nitrogen at pressures up to 9 MPa. I. Inter-branch interference effect
- 2002
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171. ; 75:6-7, s. 763-769
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Tidskriftsartikel (refereegranskat)abstract
- An improved model for pure rotational coherent anti-Stokes Raman scattering (CARS) has been developed or the dual-broadband approach. This model takes into account the fact that coherent anti-Stokes as well as Stokes radiation are generated simultaneously, and these two branches overlap and interact at high pressures giving rise to an inter-branch interference effect. In combustion studies, the anti-Stokes branch is used to determine temperature and concentrations of key species, of which nitrogen is the most widely used, and we have found that the interference effect on the anti-Stokes side is of such magnitude that it clearly needs to be taken into account at pressures of a few MPa. The necessary modifications to the total third-order susceptibility are presented and a derivation of the convolution integral for a finite-bandwidth pump source is given.
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| 2. |
- Afzelius, Mikael, et al.
(författare)
-
Dual-broadband rotational CARS modelling of nitrogen at pressures up to 9 MPa. II. Rotational Raman line widths
- 2002
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171. ; 75:6-7, s. 771-778
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Tidskriftsartikel (refereegranskat)abstract
- Rotational coherent anti-Stokes Raman spectroscopy (CARS) is a well-established spectroscopic technique for thermometry at pre-combustion temperatures an atmospheric pressure. However, at pressures of several MPa, a previous investigation revealed large discrepancies between experimental data and the theoretical model. A re-evaluation has been made of these data (at room temperature and in the range 1.5-9 MPa) with two improvements to the spectral code. The first is the inclusion of an inter-branch interference effect, which is described in detail in Paper I. The second is the use of experimental S-1-branch Raman line widths measured at 295 K, with a temperature dependence extracted from semi-classical calculations following the Robert-Bonamy formalism. It is shown that these two modifications significantly improve the theoretical model, since both the spectral fits and the accuracy of the evaluated temperatures are considerably improved.
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