Chapter 24 - Chapter 24 Introduction to Spectrochemical...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 24 Introduction to Spectrochemical Methods Measurements based on light and other forms of electromagnetic radiation are widely used throughout analytical chemistry. The interactions of radiation and matter are the subject of the science called spectroscopy . Spectroscopic analytical methods are based on measuring the amount of radiation produced or absorbed by molecular or atomic species of interest.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Classification We can classify spectroscopic methods according to the region of the electromagnetic spectrum involved in the measurement. The regions include γ –ray, X-ray, ultraviolet (UV), visible, infrared (IR), microwave, and radio frequency (RF). Spectrochemical methods have provided the most widely used tools for the elucidation of molecular structure as well as the quantitative and qualitative determination of both inorganic and organic compounds.
Background image of page 2
Properties of Electromagnetic Radiation Electromagnetic radiation is a form of energy that is transmitted through space at enormous velocities. Electromagnetic radiation can be described as a wave with properties of wavelength, frequency, velocity, and amplitude. In contrast to sound waves, light requires no supporting medium for its transmission; thus, it readily passes through a vacuum. Electromagnetic radiation can be treated as discrete packets of energy or particles called photons or quanta . These dual views of radiation as particles and waves are not mutually exclusive but complementary.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
The Speed of Light In a vacuum, the velocity (c) of light is 2.99792 x 10 8 m s -1 and the velocity of light in air is about 0.03% less. Thus, for a vacuum, or for air, the velocity of light: c = νλ = 3.00 x 10 8 m s -1 = 3.00 x 10 10 cm s -1 In a medium containing matter, light travels with a velocity less than c because of interaction between the electromagnetic field and electrons in the atoms or molecules of the medium. Since the frequency of the radiation is constant, the wavelength must decrease as the light passes from a vacuum to a medium containing matter. The wavenumber ν is another way to describe electromagnetic radiation. It is defined as the number of waves per centimeter and is equal to 1/ λ . The ν has the units of reciprocal centimeters (cm -1 ) -
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
The particle Nature of Light: Photons In many radiation/matter interactions, it is useful to consider light as consisting of photons or quanta. We can relate the energy of photon to its wavelength, frequency, and wavenumber by E = h ν = hc/ λ = hc ν where, h is Planck’s constant (6.63 x 10 -34 J s). The wavenumber ν and frequency ν , in contrast to the wavelength λ , are directly proportional to the photon energy E. The radiant power of a beam of radiation is directly proportional to the number of photons per second.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The Electromagnetic Spectrum The electromagnetic spectrum covers an enormous range of energies (frequencies) and thus wavelengths. Useful frequencies vary from > 10 19 Hz ( γ -ray) to 10 3 Hz (radio waves). An X- ray photon ( ν 3 x 10 18 Hz, λ 10 -10 m), for example, is approximately 10,000 times as
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/09/2010 for the course CHEM 3245 taught by Professor Anwara.bhuiyan during the Spring '10 term at Arkansas Tech.

Page1 / 50

Chapter 24 - Chapter 24 Introduction to Spectrochemical...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online