15NT303E Molecular spectroscopy and its Applications Fifth Semester, (Odd semester)

Transcription

1 . SRM University Faculty of Engineering and Technology Department of Physics and Nanotechnology 15NT303E Molecular spectroscopy and its Applications Fifth Semester, (Odd semester) tailed Session Plan Unit I: Basics of Spectroscopy Electromagnetic Radiation- Absorption and Emission of radiation- Line width and Line Broadening- Interpretation of Electron spin- Interpretation of Nuclear spin - Born-Oppenheimer approximation - Translational motion - Rotational motion - Vibrational motion Session. No Topics to be covered Ref Instruction Objective Program Outcome 1 2 Electromagnetic Radiation Absorption and Emission of radiationapplications Peter Atkins, Julio de Paula Atkins, Physical hemistry, W.. Freeman and ompany, New York, 2010 Acquire knowledge inthe basic concepts of atomic and molecular spectra an ability to apply knowledge of mathematics, science, and engineering 3 Line width and Line Broadening- 4 5 Interpretation of Electron spin Interpretation of Nuclear spin 6 Born-Oppenheimer approximation 7 Translationa l motion

2 8 Rotational motion 9 Vibrational motion Unit II: Atomic Structure and Atomic Spectra Structure and spectra of hydrogenic atoms -Atomic orbitals and their energies -Spectroscopic transitions and selection rules- Structures of many-electron atoms Orbital approximation - Self consistent field orbitals -Spectra of complex atomssinglet and triplet states - Spin orbit coupling- Impact on astrophysics: spectroscopy of stars Session. No Topics to be covered Ref Instruction Objective Program Outcome Structure spectra hydrogenic atoms and of Atomic orbitals and their energies Spectroscopic transitions and selection rules Peter Atkins, Julio de Paula Atkins, Physical hemistry, W.. Freeman and ompany, New York, Acquire knowledge inthe basic concepts of atomic and molecular spectra. omprehend the principles of underlying spectra of atoms and molecules.. an ability to apply knowledge of mathematics, science, and engineering 13 Structures of manyelectron atoms an ability to identify, formulate, and solve engineering problems 14 Orbital approximation Self consistent field orbitals Spectra of complex atoms 17 singlet and triplet 18 Spin orbit coupling- Unit III: Rotational Andvibrational Spectroscopies Pure rotation spectra -Rotational transitions -. Rotational Raman spectra - Molecular vibrations - Vibration rotation spectra - Vibrational Raman spectra of diatomicmolecules - Infrared absorption spectra of polyatomicmolecules - Vibrational Raman spectra of polyatomic molecules,- Symmetry aspects of molecular vibrations

3 Session. No Topics to be covered Ref Instruction Objective Program Outcome Pure rotation spectra Rotational transitions Rotational Raman spectra Molecular vibrations Vibration rotation spectra 24 Vibrational Raman spectra of diatomicmolecules Peter Atkins, Julio de Paula Atkins, Physical hemistry, W.. Freeman and ompany, New York, ollin Banwell, Mc ash, Fundamentals of Molecular Spectroscopy, McGraw ill publishing, 2001 Acquire knowledge inthe basic concepts of atomic and molecular spectra. omprehend the principles of underlying spectra of atoms and molecules.. an ability to apply knowledge of mathematics, science, and engineering an ability to identify, formulate, and solve engineering problems Emphasize the significance of various spectroscopic techniques 25 Infrared absorption spectra of polyatomicmolecules 26 Vibrational Raman spectra of polyatomic molecules, Symmetry aspects of molecular vibrations Unit IV: Electronic Spectroscopy The electronic spectra of diatomic molecules -Franck-ondon factors -. The electronic spectra of polyatomic molecules -. ircular dichorism spectroscopy -. Fluorescence - Phosphorescence -. Impact on biochemistry: fluorescence Microscopy - Dissociation and predissociation, Principles of laser action Session. No Topics to be covered Ref Instruction Objective Program Outcome The electronic spectra of diatomic l l Franck- ondon factors Peter Atkins, Julio de Paula Atkins, Physical hemistry, W.. Freeman and ompany, New York, Acquire knowledge inthe basic concepts of atomic and molecular spectra. an ability to apply knowledge of mathematics, science, and engineering

4 The electronic spectra of polyatomic ircular dichorism spectroscopy Fluorescence Phosphorescence ollin Banwell, Mc ash, Fundamentals of Molecular Spectroscopy, McGraw ill publishing, 2001 omprehend the principles of underlying spectra of atoms and molecules an ability to identify, formulate, and solve engineering problems Impact biochemistry on 34 Dissociation Unit V: Magnetic Resonance Spectroscopy Effect of magnetic fields on electrons and nuclei -Energies of electrons in magnetic fields - Energies of nuclei in magnetic fields-. Magnetic resonance spectroscopy-. Nuclear magnetic resonance-. NMR spectrometer-. hemical shift, Fine structure -. Impact on medicine: magnetic resonance imaging Session. No Topics to be covered Ref Instruction Objective Program Outcome Effect of magnetic fields on electrons and nuclei Peter Atkins, Julio de Paula Atkins, Energies of electrons in magnetic fields Energies of nuclei in magnetic fields Magnetic resonance spectroscopy Nuclear magnetic resonance Physical hemistry, W.. Freeman and ompany, New York, ollin Banwell, Mc ash, Fundamentals of Molecular Spectroscopy, McGraw ill publishing, 2001 Acquire knowledge inthe basic concepts of atomic and molecular spectra. omprehend the principles of underlying spectra of atoms and molecules.. an ability to apply knowledge of mathematics, science, and engineering an ability to identify, formulate, and solve engineering problems

5 40 NMR spectromete r 41 hemical shift, Fine structure 42 Impact on medicine: magnetic resonance imaging

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7 NOTES OF LESSON Session ontents : Session 1-6 Topic : Unit-1 Instructional Objective : 1 Program Outcomes Met : a

8 UNIT-I, LETURE-1 Introduction- Basicss of Polymers: Polymers are substancess made up of recurring structural units, each of which can be regarded as derived from a specific compound called a moanomer. The number of monomeric units usually is large and variable, each sample of a given polymer being characteristically a mixture of molecules with different molecular weights. The range of molecular weights is sometimes quite narrow, but is more often very broad Basic concept-lassification of polymer From the standpoint of general physical properties, we usually recognize three types of solid polymers: elastomers, thermoplastic polymers, and thermosetting polymers. Elastomers are rubbers or rubberlike elastic materials.thermoplastic polymers are hard at room temperature, but on heating become soft and more or less fluid and can be molded. Thermosetting polymers can be molded at room temperature or above, but when heated more strongly become hard and infusible. These categories overlap considerably but are nonetheless helpful in defining general areas of utility and types of structures. The structural characteristics that are most important to determining the properties of polymers are: (1) the degree of rigidity of the polymer molecules, (2) the electrostatic and van der Waals attractive forces between thechains, (3) the degree to whichh the chains tend to form crystalline domains, and (4) the degree of cross-linking between the chains. s on the basis of microstructures, macrostructures omo and heteropolymers: UNIT-I, LETURE-2 UNIT-I, LETURE-3 conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted exclusively by rotations about formally single bonds

9 onformation Molecular orientation can be changed by rotation around the bonds note: no bond breaking needed

10 opolymers-hemistry of polymerization UNIT-I, LETURE-4 Different spatial arrangement of the side elements or groups about the backbone molecular chains Unlike conformations, the configuration cannot be changed by rotation about the covalent bonds onfiguration describes the arrangement of the identical atoms or groups around a double bond in repeated unit UNIT-I, LETURE-5 Glass transition temperature (Tg) and melting point(tm) ): Generally speaking, all linear amorphous polymers can behave as ookian elastic (glassy) materials, highly elastic (rubbery) substances or viscous melts according to the prevailing temperature of observation and time scale of experiments. Different property ranges for the same polymer at different temperatures are related to variation in the physical structures or arrangements of the chain molecules, much as a consequence of different types and degrees of deformation.

11 UNIT-I, LETURE-6 Factors affecting T g and T m: 1. hain length Each chain end has some free volume associated with it. A polymer with shorter chains will have more chain ends per unit volume, so there will be more free volume. ence Tg' for shorter chains will be lower than Tg for long chains 2. hain Flexibility A polymer with a backbone that exhibits higher flexibility will have a lower Tg. This is because the activation energy for conformational changes is lower. Therefore, conformational changes can take place at lower temperatures. 3. Side Groups Larger side groups can hinder bond rotation more than smaller ones, and therefore cause an increase in Tg. Polar groups such as l, N or O have the strongest effect. 4. Branching Polymers with more branching have more chain ends, so have more free volume, which reduces Tg, but the branches also hinder rotation, like large side groups, which increases Tg. Which of these effects is greater depends on the polymer in question, but Tg may rise or fall. 5. ross-linking ross-linking reduces chain mobility, so Tg will be increased. It also affects the macroscopic viscosity of the polymer, since if there are cross-links between the chains, then they are fixed relative to each other, so will not be able to slide past each other. 6. Plasticisers Small molecules, typically esters, added to the polymer increase the chain mobility by spacing out the chains, and so reduce Tg. UNIT-I, LETURE-7 Molecular weights and degree of polymerization

12 M n = total wt of polymer total #of molecules n n = xini M = m n n w M = w ini = m w where m = average molecular weight of repeat unit m = Σf m i i UNIT-I, LETURE-8&9 Freee radical polymerization Reactions of polymerization, kinetics of polymerization: R + R initiation free radical monomer (ethylene) R + R propagation dimer

13 Initiator: example - benzoyl peroxide O O 2 O two or more monomers polymerized together random A and B randomly vary in chain alternating A and B alternate in polymer chain block large blocks of A alternate with large blocks of B graft chains of B grafted on to A backbone A B