IGNOU MCH-020 Atomic and Molecular Spectroscopy · 2026–27 Session
MCH-020 introduces
students to the fundamental principles and applications of Atomic and
Molecular Spectroscopy. The course explores how electromagnetic radiation
interacts with matter and how spectroscopic techniques are used to study the
structure, composition, and properties of atoms and molecules.
The course helps students understand important spectroscopic methods, including rotational, vibrational, electronic, and magnetic resonance spectroscopy, along with their applications in chemical analysis, structural determination, and scientific research.
|
Course
Code |
Applicable
Session |
Maximum
Marks |
Assignment
Code |
|
MCH-020 |
2026–27
Session |
100 |
MCH-020/TMA/2026-27 |
Key Areas of Study in
MCH-020:
1. Fundamentals
of Spectroscopy – Understand the interaction of
electromagnetic radiation with matter, energy levels, and the basic principles
of spectroscopy.
2. Rotational
and Vibrational Spectroscopy – Study rotational and
vibrational transitions and understand their applications in determining
molecular structure.
3. Electronic
Spectroscopy – Understand electronic transitions in
atoms and molecules, UV-Visible spectroscopy, and the factors affecting
electronic spectra.
4. Atomic
Spectroscopy – Study atomic absorption, atomic
emission, and related spectroscopic techniques used for elemental analysis.
5. Magnetic
Resonance Spectroscopy – Understand the basic principles of
Nuclear Magnetic Resonance (NMR) and Electron Spin Resonance (ESR/EPR)
spectroscopy.
6. Applications
of Spectroscopy – Explore the use of spectroscopic
techniques in structural analysis, qualitative and quantitative analysis,
chemical identification, and scientific research.
IGNOU MCH-020 Atomic and
Molecular Spectroscopy | SOLVED ASSIGNMENT 2026-27
Note: Answer
all the questions given below.
You may use the following whenever required:
ℎ =6.626×10-34 𝐽𝑠; 𝑚𝑒 = 9.11×10−31 𝐾𝑔; 𝑐 = 3.0×108 𝑚𝑠−1
Q1. a) A photon of violet light has a wavelength of 500 nm.
Calculate its energy.
b) State
the Lambert’s Law and translate it into a mathematical expression.
Q2. a) Explain the vector nature of orbital angular momentum.
Predict the values of magnetic quantum number. With the help of a suitable
diagram explain the concept of total angular momentum.
b) What is
Stark Effect? In which condition do we get linear stark effect and quadratic
stark effect?
Q3. a) Following spectra gives the relative positioning and
intensity of the 2s peaks? Which of the following statements explain it best?
i) Be has a
greater nuclear charge than Li and more electrons in the 2s orbital.
ii) Be
electrons experience greater electron-electron repulsions than Li electrons.
iii) Li has
a greater nuclear attraction on the 2s electrons, so it is harder to remove
those
iv) Li has
greater electron shielding by the 1s orbital, so the 2s electrons can be easily
removed.
b) With the
help of suitable diagrams explain the rotation of BF3 molecule as an example of
an oblate symmetric top molecule.
Q4. a) The first line in the rotational spectrum of HF molecule is
observed to be at 60.22 cm-1. Calculate the location of
the band in DF molecule obtained by isotopic substitution of H atom in HF by D.
Assume that there is no change in the bond length of the molecule.
b) The
oscillation frequency of 1H35Cl is determined to be 3660
cm-1. (Given: Atomic mass of Hydrogen: 1.008 u; atomic mass of 35Cl=34.969
u)
Q5. a) What is meant by anharmonic oscillator? Apart from
mechanical anharmonicity may arise? Why does it arise? With the help of a
diagram show the allowed absorption transitions for an anharmonic oscillator
according to the selection rule.
b) What is
meant by Fermi resonance? When are hot bands observed in transitions? Derive
the expression for the frequency of a hot band under anharmonic conditions.
Q6. a) The Raman line for a substance was observed at 546.4 nm on
irradiating with 322.4 nm radiation. Calculate the wave numbers of Stokes and
anti-Stokes lines for the substance if the exciting line has a wavelength of
328.5 nm.
b) Explain the coherent anti-Stokes Raman Spectroscopy (CARS) technique. Give
suitable illustrations.
Q7. a) Illustrate the general procedure for determining the term
symbols for (sg)1 and (pu)3.
b) The
vibrational frequency and anharmonicity constant of HF molecule in an excited
electronic state are found to be 3456.25 cm-1 and 0.030 respectively.
Calculate the dissociation energies, (De) and (D0) of the
HF molecule in this excited state.
Q8. a) Explain the different mechanisms in fluorescence quenching.
b) (i)
Describe the Nuclear Overhauser Effect (NOE) and its significance in structural
elucidation using NMR.
(ii)
Predict the number of signals in 13C-NMR spectrum in the following compounds.
I.
2,3-Dimethylbuta-1,3-diene
II.
Cyclohexanol
III.
p-Xylene
IV.
Ethylbenzene
V.
But-1-ene
VI. Pyrrole
Q9. a) (i) Free Mössbauer nucleus ¹¹⁹Sn emits a γ-radiation of
frequency 5.76 × 10¹⁸ Hz. Calculate therecoil velocity and energy of the
nucleus. [Given: Avogadro number = 6.02 × 10²³ mol⁻¹].
(ii) For a
system with an axially symmetric electric field gradient, derive the energy
level scheme and determine the resulting quadrupole splitting for a transition
from a ground state with spin 𝑰𝒈𝒓 = 𝟑/𝟐 to an excited state with spin I𝒆𝒙 = 𝟓/𝟐.
b) (i) The
ESR spectrum of an organic radical containing two carbon atoms consisted of 12
lines having relative intensities of 1,2,3,1,6,3,3,6,1,3,2 and 1. Identify the
radical.
(ii) Why
does the g value in ESR spectroscopy become anisotropic in solid samples or
molecules with low symmetry?
Q10. a) What is Nuclear Overhauser Effect (NOE)? How does it arise.
b) In the
ESR spectrum of K3Mo (CN)8, 25% isotopes of Mo show in
spin I= 5/2. Predict the pattern of lines around a central line from 75%
non-magnetic isotope.
Frequently Asked
Questions
Question 1. What is
MCH-020?
Answer:
MCH-020 is an IGNOU course titled Atomic and Molecular Spectroscopy. It
focuses on the principles, techniques, and applications of spectroscopy for
studying the structure and properties of atoms and molecules.
Question 2. What is the
assignment code for MCH-020?
Answer:
The assignment code for the 2026–27 Session is MCH-020/TMA/2026-27.
Question 3. How many
marks is the MCH-020 assignment worth?
Answer:
The MCH-020 Tutor Marked Assignment carries a maximum of 100 marks.
Question 4. Which topics
should students focus on for MCH-020?
Answer: Students
should focus on the Fundamentals of Spectroscopy, Electromagnetic Radiation,
Rotational Spectroscopy, Vibrational Spectroscopy, Electronic Spectroscopy,
Atomic Spectroscopy, UV-Visible Spectroscopy, NMR, ESR/EPR, and Spectroscopic
Applications.
Question 5. Why is
MCH-020 important?
Answer: MCH-020
helps students understand how spectroscopic techniques are used to investigate
atomic and molecular structures. It provides essential knowledge for chemical
identification, structural determination, qualitative and quantitative
analysis, and scientific research.
Need help preparing for
MCH – 020?
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