Vol. 27, issue 05, article # 3

Abstract:

Wall-collision broadening and shift of the water vapor absorption lines was measured within 5000–5600 cm^–1 with the IFS 125 HR Fourier spectrometer. It has been shown, that tight confinement of the molecules by the nanopores of silica aerogel leads to the strong lines broadening and shift. The half-widths at half maximum of spectral lines of the water vapor under nano-environment are on the average 23 times larger than those for the free molecules at a pressure of 10 mbar.
A model that simulates the absorption profile of H₂O molecule, confined in nanopores, is presented. It assumes that half-width Г of the absorption H₂O molecule is a sum of two parts, Г_Wall and Г_if. The first part, Г_Wall, is connected with the wall collisions and it gives the main contribution to the half-width for all absorption lines. The best correlation between experimental and calculated half-widths is obtained when the second rotationally depended part, Г_if, is connected with the collisions between (H₂O) molecules having (in comparison with free H₂O molecules) modified electro-optical parameters due to influence of pore’s surface. The data on the half-widths and center shifts for some strongest H₂O lines have been presented. The agreement between calculated and experimental half-width is satisfactory.

Keywords:

water vapor, spectral line broadening, aerogel, nanopores

References:

1. Henderson M.A. The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited // Surface Sci. Reports. 2002. V. 46, iss. 1–8. P. 5–308.
2. Ohba T., Kaneko K. Cluster-associated filling of water molecules in slit-shaped graphitic nanopores // Mol. Phys. 2007. V. 105, iss. 2–3. P. 139–145.
3. Raghunathan A.V., Aluru N.R. An empirical potential based quasicontinuum theory for structural prediction of water // J. Chem. Phys. 2009. V. 131, iss. 18. P. 184703-1–184703-7.
4. Mosaddeghi H., Alavi S., Kowsari M.H., Najafi B. Simulations of structural and dynamic anisotropy in nano-confined water between parallel graphite plates // J. Chem. Phys. 2012. V. 137, iss. 18. P. 184703-1–184703-10.
5. Rasaiah J.C., Garde S., Hummer G. Water in nonpolar confinement: from nanotubes to proteins and beyond // Annu.  Rev.  Phys.  Chem. 2008.   V. 59,  iss. 1.  P. 713–740.
6. Coudert F.-X., Vuilleumier R., Boutin A. Dipole moment, hydrogen bonding and IR spectrum of confined water // Chem. Phys. Chem. 2006. V. 7, iss. 12. P. 2464–2467.
7. Kocherbitov V. Properties of Water Confined in an Amphiphilic Nanopore // J. Phys. Chem. C. 2008. V. 112, iss. 43. P. 16893–16897.
8. Littl L. Infrakrasnye spektry adsorbirovannyh molekul. M.: Mir, 1969. 516 p.
9. Kiselev A.V., Lygin V.I. Infrakrasnye spektry poverhnostnyh soedinenij. M.: Nauka, 1972. 459 p.
10. Uillis R. Fizika poverhnosti: kolebatel'naja spektroskopija adsorbentov / Pod red. R. Uillisa. M.: Mir, 1984. 247 p.
11. Svensson T., Lewander M., Svanberg S. Laser absorption spectroscopy of water vapor confined in nanoporous alumina: wall collision line broadening and gas diffusion dynamics // Opt. Express. 2010. V. 18, iss. 16. P. 16460–16473.
12. Ponomarev Yu.N., Petrova T.M., Solodov A.M., Solodov A.A. IR spectroscopy of water vapor confined in nanoporous silica aerogel // Opt. Express. 2010. V. 18, iss. 25. P. 26062–26067.
13. Perez-Hernandez N., Luong T.Q., Perez C., Martin J.D., Havenith M. Pore size dependent dynamics of confined water probed by FIR spectroscopy // Phys. Chem. Chem. Phys. 2010. V. 12, iss. 26. P. 6928–6932.
14. Xu C.T., Lewander M., Andersson-Engels S., Adolfs-son E., Svensson T., Svanberg S. Wall-collision line broadening of molecular oxygen within nanoporous materials // Phys. Rev. A. 2011. V. 84, iss. 4. P. 042705-1– 042705-4.
15. Hartmann J.-M., Sironneau V., Boulet C., Svensson T., Hodges J.T., Xu C.T. Collisional broadening and spectral shapes of absorption lines of free and nanopore-confined O2 gas // Phys. Rev. A. 2013. V. 87, iss. 3. P. 032510-1–032510-10.
16. Fano U. Pressure broadening as a prototype of relaxation  //  Phys.  Rev.  1963.  V. 131,  iss. 1.  P. 259–268.
17. Buldyreva J., Lavrenteva N., Starikov V. Collisional Line Broadening and Shifting of Atmospheric Gases. A practical Guide for Line Shape Modeling by Current Semi-Classical Approaches. London: Imperical College Press, 2010. 304 p.
18. Ptashnik I.V., Smith K.M., Shine K.P. Self-Broadened Line Parameters for Water Vapour in the Spectral Region 5000–5600 cm–1 // J. Mol. Spectrosc. 2005. V. 232, iss. 2. P. 186–201.
19. Olivero J.J., Longbothum R.L. Empirical fits to the Voigt line width: A brief review // J. Quant. Spectrosc. Radiat. Transfer. 1977. V. 17, iss. 2. P. 233–236.
20. Tsao C.J., Curnutte B. Line-widths of pressure-broadened spectral lines // J. Quant. Spectrosc. Radiat. Transfer. 1962. V. 2, iss. 1. P. 41–91.
21. Townes C.H., Schawlow A.L. Microwave Spectroscopy. New York; London; Toronto: McGraw-Hill Book Company, 1955. 698 p.
22. Wagner P.E., Somers R.M., Jenkins J.L. Line Broa-dening and Relaxation of Three Microwave Transitions in Ammonia by Wall and Intermolecular Collisions // J. Phys. B. 1981. V. 14, iss. 24. P. 4763–4770.
23. Luijendijk S.C.M. The Effect of Wall Collisions on the Shape of Microwave Absorption Lines // J. Phys. B. 1975. V. 8, iss. 18. P. 2995–3000.
24. Coy S.L. Speed Dependence of Microwave Rotational Relaxation Rates // J. Chem. Phys. 1980. V. 73, iss. 11. P. 5531–5555.
25. Robert D., Bonamy J. Short range force effects in semiclassical molecular line broadening calculations // J. de Physique. 1979. V. 40, N 10. P. 923–943.
26. Leavitt R.P. Pressure broadening and shifting in microwave and infrared spectra of molecules of arbitrary symmetry: An irreducible tensor approach // J. Chem. Phys. 1980. V. 73, N 11. P. 5432–5450.
27. Starikov V.I. Calculation of the self-broadening coefficients of water vapor absorption lines using an exact trajectory model // Opt. Spectrosc. 2008. V. 104, N 4. P. 513–523.
28. Hammaker R.M., Francis S.A., Eischens R.P. Infrared study of intermolecular interactions for carbon monoxide chemisorbed on platinum // Spectrochim. Acta. 1965. V. 21, N 7. P. 1295–1309.
29. Crossley A., King D.A. Infrared spectra for co isotopes chemisorbed on Pt «111»: Evidence for strong absorbate coupling interactions // Surface Sci. 1977. V. 68. P. 528–538.
30. Mahan G.D., Lucas A.A. Collective vibrational modes of adsorbed CO // J. Chem. Phys. 1978. V. 68, N 4. P. 1344–1348.
31. Scheeffler M. The influence of lateral interactions on the vibrational spectrum of adsorbed CO // Surface Sci. 1979. V. 81, N 2. P. 562–570.
32. Svensson T., Adolfsson E., Burresi M., Savo R., Xu C.T., Wiersma D.S., Svanberg S. Pore size assessment based on wall collision broadening of spectral lines of confined gas: experiments on strongly scattering nanoporous ceramics with fine-tuned pore sizes // Appl. Phys. B. 2013. V. 110, N 2. P. 147–154.