Abstract
Vibrational Raman spectroscopy is a very usful technique for studying the dynamical behavior of a system, in particular in the critical region. In a mixture, composition fluctuations play an important role and on the basis of the results for pure substances one would expect an increase of the linewidth in approaching the critical point. However, in previous experiments such an effect was not detected. The reasons for this failure will be discussed. Recently, we have observed a considerable broadening of the linewidth in approaching the critical point in the system helium-nitrogen under high pressure. However, it is well-known that broadening may occur through various other mechanisms such as changes in density, composition fluctuations far from the critical point, aggregation, etc. On the basis of the helium-nitrogen data the pitfalls in the experimental determination of critical broadening are discussed. The data analysis takes into account the contribution of noncritical effects. Consequences are drawn for the interpretation of spectroscopic data in terms of concentration of species in supercritical solvents. Moreover, we discuss the possibility of a difference between the local composition and the bulk composition and demonstrate from our line shift data that this is not a critical effect.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
D. Schiferl R. LeSar and D. S. Moore, inSimple Molecular Systems at Very High Density, A. Polian, P. Loubeyrc, and N. Boccara. eds. (Plenum, New York. 1989), p. 303.
M. Clouter.Annu. Rev. Phys. Chem. 39:69 (1988).
J. Chesnoy and M. Gale.Adv. Chem. Phys. 70:297 (1988).
B. P. Hills and P. A. Madden.Mol. Phys. 37:937 (1979).
M. J. Clouter and H. Kiefle.Phys. Rev. Lett. 52:763 (1984).
K. A. Wood and H. L. Strauss.J. Chem. Phys. 74:6027 (1981); J. R. Petrula. H. L. Strauss. K. Q.-H. Lao. and R. Pecora.J. Chem. Phys. 68:623 (1978).
H. J. van Elburg and J. D. van Voorst.Chem. Phys. 113:463 (1987).
B. P. Hills,Mol. Phys. 37:949 (1979).
D. W. Oxtoby,Annu. Rev. Phys. Chem. 32:77 (1981).
W. Knapp and S. Fisher.J. Chem. Phys. 76:4730 (1982).
M. J. Clouter, H. Kiefte. and R. K. Jain.J. Chem. Phys. 73:673 (1980).
S. R. I. Brueck.Chem. Phys. Len. 50:516 (1977).
P. Loubeyre, R. LeToullec, and J. P. Pinceaux,Phys. Rev. B 45:12844 1992).
S. Mukamel, P. S. Stern, and D. Ronis.Phys. Rev. Lett. 50:590 (1983); M. J. Clouter and H. Kiefte.J. Chem. Phys. 66:1736 (1977).
B. Khalil-Yahyavi. M. Chatelet, and B. Oksengorn,J. Chem. Phys. 89:3573 (1988).
L. J. Callego. J. A. Somoza, and M. C. Blanco,Z. Naturforsch. 43a:847 (1988).
H. L. Strauss and S. Mukamel.J. Chem. Phys. 80:6328 (1984).
C. B. Roberts, I. E. Chateauneuf. and J. F. Brennecke,J. Am. Chem. Soc. 114:8455 (1992).
W. L. Vos and J. A. Schouten,Physica A 182:365 (1992).
L. J. Muller. D. Vanden Bout, and M. Berg,J. Chem. Phys. 99:810 (1993).
H. Burstyn and J. V. Sengers.Phys. Rev. A 25:448 (1982).
R. Kubo, inFluctuation. Relaxation, and Resonance in Magnetic Systems, D. ter Haar, ed. (Olivet & Boyd. Edinburgh, 1962).
M. I. M. Scheerboom and J. A. Schouten, Plats. Rev. E51 (in press).
A. Kumar, H. R. Krisnamurthy. and E. S. Gopal,Phys. Rep. 98:57 (1983).
J. H. Lunacek and D. S. Cannell.Phys. Rev. Lett. 27:841 (1971).
W. Zhang and J. A. Schouten. unpublished.
J. Chesnoy,Chem. Phys. Lett. 125:267 (1986): J. Chesnoy and G. M. Gale,Adv. Chem. Phys. 70:397 (1988).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Schouten, J.A., Scheerboom, M.I.M. Broadening of the vibrational linewidth in a mixture due to critical concentration fluctuations. Int J Thermophys 16, 585–598 (1995). https://doi.org/10.1007/BF01438844
Issue Date:
DOI: https://doi.org/10.1007/BF01438844