Electronic spin resonance (ESR)

Electronic spin resonance:-
         Region- microwave
It is know as EPR (electronic peramagnetic resonance ) the mechanism EPR IS Similarly NMR both ESR and NMR spectroscopy is called magnetic field are use in both spectroscopy , because magnetic field are use in both spectroscopy
ESR Active species :-
                                      The molecule ions or radical which contain unpaired electron are ESR active because the their total spin quantum number is not zero
By the help of ESR spectroscopy we can determine various species which contain at list one unpaired electron
Note:- NMR spectroscopy use electromagnetic wave  radio waves
ESR spectroscopy use electromagnetic wave -micro wave
Theory of ESR :-
                              If a molecule contain unpaired electron then molecule is ESR active
When we put a molecule in a magnetic field then angular momentum it generated due to the rotation of electron
The magnetic field can orientent in the direction of angular momentum and external magnetic may be parallel anti parallel from each other
The energy of electron in magnetic field which genrate angular momentum can be given as

               E= gBHMs
Where
              -  g = spectroscopic coefficient
                 B= Bohr magneton
                H = applied magnetic field
                 Ms = spin angular quantum number
From it the given energy profile diagram we can say that
The energy strength with Ms= -1/2
as lower energy because the orientation spin angular momentum parallels with applied magnetic field.
The energy strength with Ms = +1/2 as higher energy because the orientation of spin angular momentum and applied magnetic field is anti parallel
So the transition between low energy strength is possible by absorption of energy in microwave region.
The amount of energy which is required for transition is given as-
     ^E = E2-E1
  = 1/2gBHMs-(-1/2gBHMs)
=   ^E = gBHMs
   = hv = gBHMs
👉ESR  Spectrum:-
                                   ESR spectrum is a simple graph which is flowed strength intensity of lines
The intensity of lines depends on obserptoin of energy so the formations of ESR spectrum is represented in the given diagram.

ESR spectrum is always records in first order derivative form because due to the transition in the electronic spin we observe a broad signal in normal ESR obserptoin spectrum. And it is very difficult to find out the spectrum so we plot a graph between slope dy/dx and the strength on the magnetic field is known as first derivative ESR spectra.
Hyperfine splitting in the ESR spectra :-
                                                In unpaired electron on a molecule / ion / radical them itintract various nucleas which have I=not zero
The interaction of electron spin with nuclear spin is known as hyper fine splitting.
The total splitting in ESR can be given as
       (   Total splitting  = 2ni+1)

  Hyperfine splitting :-
                                            Selection rule =
                            Mi=0.      Ms = +_1
The hyperfine splitting in ESR spectra can be explain by the following example
H-atom
Total splitting = 2ni +1
                            2×1×1/2+1
                         = 2

Zero field splitting :=
                                        The molecule which contain unpaired electron is ESR active
The coupling of electron spin with nuclear spin which is called hyperfine splitting.
If a molecule contain two or more unpaired electron then coupling between two electron spin is also take place this type of coupling is called electron -electron coupling and splitting due to this coupling is called zero field splitting.

इलेक्ट्रॉनिक स्पिन अनुनाद: -

         क्षेत्र- माइक्रोवेव

इसे EPR (इलेक्ट्रॉनिक पेरामैग्नेटिक रेजोनेंस) के रूप में जाना जाता है, तंत्र EPR IS इसी प्रकार NMR ESR और NMR स्पेक्ट्रोस्कोपी दोनों को कहा जाता है चुंबकीय क्षेत्र दोनों स्पेक्ट्रोस्कोपी में उपयोग किया जाता है, क्योंकि दोनों स्पेक्ट्रोस्कोपी में चुंबकीय क्षेत्र का उपयोग किया जाता है

ईएसआर सक्रिय प्रजातियां: -

                                      अणु आयन या कट्टरपंथी जिनमें अप्रकाशित इलेक्ट्रॉन होते हैं, ESR सक्रिय होते हैं क्योंकि उनकी कुल स्पिन क्वांटम संख्या शून्य नहीं होती है

ईएसआर स्पेक्ट्रोस्कोपी की मदद से हम विभिन्न प्रजातियों को निर्धारित कर सकते हैं जिनमें सूची में एक अप्रकाशित इलेक्ट्रॉन होता है

नोट: - एनएमआर स्पेक्ट्रोस्कोपी विद्युत चुम्बकीय तरंग रेडियो तरंगों का उपयोग करते हैं

ESR स्पेक्ट्रोस्कोपी विद्युत चुम्बकीय तरंग -micro लहर का उपयोग करते हैं