Handbook of Analytical Techniques in Concrete Science and Technology 14379_05文档.pdfVIP

5 IR Spectroscopy S. N. Ghosh 1.0 INTRODUCTION Infrared spectroscopy (IR) is used in the areas of determination of molecular structure, identification of chemical species, quantitative/quali- tative determination of chemical species, and in a host of other applications. This technique is used in the investigation of matter in the solid, liquid, and gaseous states. The application of IR is well known in the fields of chemistry, physics, materials science, etc. The application of this technique in the field of cement and concrete dates back to the Tokyo Symposium (1968). Though comparatively new in cement and concrete, IR study is gaining much importance with the advent of user-friendly equipment and continuing research on identification and characterization of reaction products, new materials, etc. Raman spectroscopy, a complementary to IR technique, is briefly described in this chapter. 2.0 THEORY If a molecule is placed in an electromagnetic field (e.g., light), a transfer of energy from the field to the molecule will occur only when Bohr’s frequency condition is satisfied. 174 IR Spectroscopy 175 E = hν where h = Planck’s constant ν = frequency of light In the case of a diatomic molecule, it can be proven from mechanical considerations that the vibrations of the two nuclei in a diatomic molecule are equivalent to the motion of a single particle of mass, µ, whose displacement from its equilibrium position is equal to the change of the internuclear distance. The termµ is called thereduced mass and is given by: 1/µ = 1/m1 + 1/m2 where m and m are masses of the two nuclei. 1 2 The kinetic energy, T, is then: