Principle of UV -visible Spectroscopy

Principle of UV visible spectroscopy

Principle of UV -visible spectroscopy states that the absorption of electromagnetic radiations in the UV and visible region excites the electron from lower electronic level to higher electronic level called as electronic transitions. Since it involves electronic transitions, it is also known as electronic spectroscopy.

The electronic transitions are also accompanied by vibrational and rotational transitions.

The amount of light absorbed is given by Beer-Lambert's law which states that:

logI0/I = A = Ɛcl

Where,

I0 = intensity of incident light

I = intensity of transmitted light

A = Absorbance

Ɛ = Molar absorptivity Coefficient or extinction Coefficient

c = concentration

l = path length

Comments

Gross and Specific Selection rules for different molecular spectroscopies

Gross selection rule tells whether a molecule will be active or inactive in a particular Spectroscopy. Specific selection rule tells about the allowed changes in the magnitude of energy when it is active in a particular Spectroscopy. Rotational or Microwave Spectroscopy Gross selection rule: permanent dipole moment Specific selection rule: ∆J = +1 or -1 ( for rigid rotor) 2. Vibrational or IR Spectroscopy Gross selection rule: change in dipole moment during vibrations Specific selection rule: ∆v = +1 or -1 ( for harmonic oscillator) 3. Raman Spectroscopy Gross selection rule: change in polarizability Specific selection rule: ∆J = 0, +2 or -2 ∆v = +1 or -1 4. Electronic or UV-Visible Spectroscopy Gross selection rule: No stringent rule Specific selection rule: ∆s = 0 and ∆l = +1 or -1 5. Nuclear Magnetic Resonance or Radio waves Spectroscopy Gross selection rule: nuclear spin should be no zero Specific se...

Flame Emission Spectrometry

In flame Emission Spectrometry, the combustion flame not only frees the atoms but it also supplies the energy necessary to move the electrons of the free atoms from ground state to excited state. The energy which is emitted by the excited atoms when returning to the ground state provides the basis for analytical determination in Flame Emission Spectrometry. Applications of Atomic Emission Spectrometry: 1. Food Industry: for detection of calcium and iron in beer . 2. Biological/Medical Applications: For determination of Na, K, Ca and Mg in body fluids and other biological samples. 3. For determination of Alkali and Alkaline Earth Metals in plant Materials, Chemicals, Cements, Oceanography and Ceramic Materials. Get best price at India Mart for spiral diaries: Spiral Diaries - https://m.indiamart.com/impcat/spiral-diaries.html?utm_source=GrowYourkids-il5kh&utm_medium=affiliate&utm_campaign=0624&utm_content=4

Atomic Absorption Spectrometry

Atomic Absorption Spectrometry is an absorption spectroscopic technique in which radiation of a particular frequency from a source is absorbed by non-excited neutral gaseous atoms generated in an atomizer in their ground state. The light is absorbed in the UV-visible region and makes transitions to higher electronic energy levels. The amount of light absorbed is quantified and this amount of absorption helps in determining the analyte concentration. (It follows Beer's Law) The concentration is measured by drawing a calibration curve after calibrating instrument with a standard of known concentration. Factors affecting the amount of light absorbed Length of path transversed Concentration of absorbing atoms in the vapour state. The diagrammatic representation of Atomic Absorption Spectrometer are shown in the below diagram: Components Used in Atomic Absorbance Spectrometer: 1. Hollow Cathode Lamp: Acts as source of radiation It is a sha...

Chemistry Notes for B.Sc. and M.Sc.

Search This Blog