18-Spectro_02_web - Harris, page 406:...

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WHEN A MOLECULE ABSORBS LIGHT - HAVING  SUFFICIENT ENERGY TO CAUSE THE ELECTRONIC  TRANSITION - VIBRATIONAL AND ROTATIONAL  TRANSITIONS OCCUR AS WELL Harris, page 406:
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………. .In an interaction that leads to absorption of radiation,   net transfer of energy   occurs between a photon and a  molecule which results in a change of internal energy of the  molecule ( E). Energy transfer: E = h ν h is Planck’s constant, 6.62 × 10 -34  J s and  ν  is the  frequency of electromagnetic radiation ( Hz , etc.)
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Components of kT at T = 300 K (room temperature). h: the Planck constant = 6.62 × 10 -34  J s R (in RT) 8 J/K mol (1 eV/atom 100 kJ/mol) It is practical to know (by the way):
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Light is seen by a molecule as an alternating electric  field
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in spectroscopy, an analytical signal is produced by exciting a sample to a higher energy level (absorption of radiation) followed by exploitation of the range of physical phenomena, such as: emission luminescence scattering diffraction Molecular (atomic) spectroscopy probes the  energy-level structure of physical systems
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the choice of the type of radiation is primarily determined by the energy range of the phenomena investigated; a spectrum of the electromagnetic radiation the result of the spectroscopic analysis is usually a spectrum that represents a functional relationship between the radiation intensity and its energy (units) among several types of spectroscopies used in analytical chemistry the most popular are: atomic and molecular
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This note was uploaded on 12/28/2010 for the course CHEMISTRY 222 taught by Professor Wieckowski during the Spring '10 term at University of Illinois at Urbana–Champaign.

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18-Spectro_02_web - Harris, page 406:...

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