Analytical Chemistry Trinidad & 

Tobago Lab Resources

EM Spectrum and Analytical Chemistry


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Spectroscopy
EM Radiation in chemistry
The EM Spectrum
The EM spectrum explained

Spectral range and electron transitions



Radiation
Type
Radiation Source Frequency Range (Hz) Wavelength Range Type of Transitions
gamma rays    1020 - 1024 <10-12 m nuclear
X-rays   1017 - 1020 0.01nm - 10nm (1 pico meter) inner electron
ultraviolet deuterium lamp 1015 - 1017 400 nm - 1 nm outer electron. Electronic transitions, vibrational fine structure
visible Tungsten lamp 4 - 7.5 x 1014 750 nm - 400 nm
near-infrared Tungsten, dye laser 1 x 1014 - 4 x 1014 2500 nm - 750 nm (2.5 um - 750 nm) outer electron molecular vibrations. Vibrational transitions, rotational fine structure
infrared nerst glower, globar, Xe,Ar, discharge lamp 1013 - 1014 250,000 - 2,500 nm (25um - 2.5 um) outer electron, molecular vibrations. Vibrational transitions, rotational fine structure
microwaves   3 x 1011 - 1013 250,000 - 1,000,000,000 nm (1 mm - 25 um) molecular rotations,electron spin flips*, Rotational transitions
radio waves   <3 x 1011 >1 mm nuclear spin flips*
* energy levels split by a magnetic field.


The Colors of Visible Radiation ¹



Wavelength Range nm Color seen by Instrument
Absorption color
Color seen by Human Eye
Complement color
400 - 465 Violet Yellowish green
465 - 482 Blue Yellow
482 - 487 Greenish blue Orange
487 - 493 Blue green Red orange
493 - 498 Bluish green Red
498 - 530 Green Red purple
530 - 559 Yellowish green Reddish purple
559 - 571 Yellow green Purple
571 - 576 Greenish yellow Violet
576 - 580 Yellow Blue
580 - 587 Yellowish orange Blue
587 - 597 Orange Greenish blue
597 - 617 Reddish orange Blue green
617 - 780 Red Blue green



Reference:
1. "Analytical Absorption Spectroscopy", D.B. Judd; M.G. Melon (Ed.)
Chap. 9, Wiley, New York, 1950.


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Signature: Dhanlal De Lloyd, Chem. Dept, The University of The West Indies, St. Augustine campus
The Republic of Trinidad and Tobago.
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