FIU CHM 4130 - CHAPTER 6A_Xiao_Introduction_to_Spectroscopy_2018 (1) (52 pages)

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Introduction to Spectroscopic Methods Part 1 Spectrometry Analytical methods based on atomic and molecular spectroscopy Spectroscopy Study of interaction between radiation electromagnetic radiation or other forms of energy such as acoustic waves and beams of particles ions and electrons and matter a branch of science 1 Radiation Wave particle duality Sinusoidal wave model Discrete particle model 2 The Electromagnetic Spectrum Kinds of Spectroscopy Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 4 What about E E h c 5 LIGHT Electro magnetic radiation 6 Light as a Wave 7 Light as a Wave Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 8 Light as a Wave Frequency determined by the source Velocity of propagation v depended upon composition of the medium Speed of light in a vacuum c 3 00 x 108 m s Wavenumber reciprocal of k Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2007 9 Effect of the Medium on a Light Wave Frequency remains the same Velocity and Wavelength change c 3 00 x 108 m s Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 10 Mathematic Description of a Wave Y A sin t A Amplitude phase angle 2 v angular frequency 2 Y A sin 2 t Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 11 Mathematic Description of a Wave Sine waves with different amplitudes and with a phase different of 90 degree Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 12 Superposition of Waves If two plane polarized waves overlap in space the resulting electromagnetic disturbance is the algebraic sum of the two waves Y A1sin 2 1t 1 A2sin 2 2t 2 1 N electromagnetic waves can be differ in frequency amplitude and phage angle 2 These waves will pass some point in space simultaneously 13 Superposition of sinusoidal wave a A1 A2 1 2 20 1 2 b A1 A2 1 2 200 1 2 Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 14 Optical Interference Constructive Interference 1 Have identical frequency 2 2 1 m2 2 1 0 or 360 deg or integer of multiple of 360 deg Destructive Interference 1 Have identical frequency 2 2 1 2m 1 2 1 180 deg or 180 plus an integer of multiple of 360 deg Figure 3 4 Ingle and Crouch Spectrochemical Analysis 15 Should be Superposition of two sinusoidal wave of different frequencies but identical amplitudes Douglas A Skoog et al Principles of Instrumental Analysis Thomson 2011 16 Superposition of sin waves to form a square wave 17 Electro magnetic radiation Light as a wave Mathematic description Superposition of waves interference 18 Diffraction Refraction and Reflection 19 Diffraction The Bending of Light as It Passes Through an Aperture or Around a Small Object Diffraction will be less and can be seen only at the edges d x y Wave will undergo the process of notable diffraction d x y 20