Introduction

• SPECTROSCOPY
• Spectroscopy


  The study of the interaction between matter (i.e. molecules/atoms) with electromagnetic radiation
• Each chemical element or compound can absorb and disperse light over a certain range of frequencies or wavelengths and every chemical element or compound has a unique characteristic spectrum
• Spectroscopy


  A method that is used to measure how much light is absorbed by a chemical substance and at what intensity of light passes through it
• Spectrometer


  The instrument which records this variation in intensity
• Absorption


  When a substance interacts with light, some of its molecules absorb the light/radiation leads to a transition from a lower to a higher E level
• The type of light wavelengths that are absorbed helps figure out how much quantity of a substance is present in the sample
• Types of spectroscopy


  • Atomic absorption spectra
  • Molecular absorption spectra
• Absorption


  The substance first absorbs the heat or energy and get excited. This causes them to become unstable
• Emission


  When the molecules do a transition from a higher to a lower level of energy and transmit (radiates) this energy as light
• Eg. Mass Spectroscopy
• Absorption spectra


  Records the wavelengths absorbed by the material
• Emission spectra


  Records wavelengths emitted by materials, which have been stimulated by energy before
• Types of spectroscopy


  • Absorption Spectroscopy
  • Emission Spectroscopy
  • Fluorescence and Phosphorescence
  • Scattering
  • Atomic Spectroscopy
  • Molecular Spectroscopy
• Electromagnetic (EM) radiation


  The form of energy that is transmitted through space at an enormous velocity
• EM radiations have both the properties of waves and particles
• Sources of EM radiations

  • Artificial sources such as cell phones, light bulbs
  • Living organisms such as humans
  • The Sun
• The large amount of energy released by the Sun supports life on Earth
• Electromagnetic (EM) Wave


  Has electric and magnetic components that oscillate in the plane perpendicular to each other. They are transverse waves that do not require a medium to travel and travel at the speed of light
• Characteristics of EM radiation

  • Wavelengths
  • Frequency
  • Velocity
  • Wavenumbers
• Wavelength


  The distance between two consecutive crests (highest point) or trough (lower points)
• Frequency


  The number of waves which can pass through a point in one second
• Wavelength and frequency


  Wavelength is inversely proportional to frequency
• Velocity of EM waves

  Dependent on the medium through which radiation passes, with a speed of light in vacuum of 3 x 10^8 m/s
• Wavenumber


  The number of waves per centimeter in a vacuum, used in infrared (IR) spectroscopy
• Electromagnetic (EM) wave energy

  Consists of discrete particles of pure energy called photons or quanta, with energy proportional to the frequency of radiation
• Types of EM radiation

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• The range of EM radiation from longest wavelength to shortest wavelength is called the Electromagnetic Spectrum
• Applications of spectroscopy


  • Environmental monitoring
  • Art conservation
  • Pharmaceutical analysis
  • Astronomy
  • Chemistry and medicine
  • Biochemistry
  • Environmental chemistry
  • Marine science
  • Material chemistry
• Frequency and wavelength


  Wavelength is inversely proportional to frequency
• Gamma waves


  Their high energy is due to their tiny wavelength
• ROY G BIV refers to the visible light spectrum
• Red and yellow


  Yellow is more energetic than red
• Gamma and radio waves

  Gamma waves travel faster than radio waves
• Microwaves


  More dangerous than radio waves because they can cause molecular vibration and heating