Rotational spectra, vibrational spectra, rotation–vibration spectra of diatomic and linear molecules, Raman spectra - experimental techniques and classical theory of Raman scattering - One Line Questions

1. Overtones in vibrational spectra arise from transitions where Δv is: — ±2
2. The fundamental vibrational transition corresponds to which change in the vibrational quantum number? — 0 → 1
3. What is the experimental setup for Raman spectroscopy typically characterized by? — A laser source and a spectrograph/monochromator
4. What is the phenomenon observed in Raman spectroscopy? — Scattering of radiation with a frequency shift
5. Which molecules can exhibit pure rotational Raman spectra? — Only molecules with a changing polarizability during rotation
6. What physical property of a molecule is directly related to the rotational constant 'B'? — Moment of inertia
7. Vibrational Raman spectra provide information about: — Bond polarizability derivatives
8. What is the primary information obtained from rotational spectra? — Molecular geometry and bond lengths
9. What are the P and R branches in a rotation–vibration spectrum? — Branches corresponding to ΔJ = -1 and ΔJ = +1 respectively
10. For linear molecules, the selection rule for vibrational Raman activity is: — Change in polarizability
11. The spacing between adjacent lines in a pure rotational spectrum of a rigid diatomic molecule is approximately: — Constant
12. In a rigid rotor model, what is the energy of a rotational level given by? — E_J = BJ(J+1)
13. In the harmonic oscillator model, what is the energy of a vibrational level given by? — E_v = ħω(v + 1/2)
14. Rotation–vibration spectra combine information from which two types of molecular motion? — Vibrational and rotational
15. A molecule that is IR active is not necessarily Raman active, and vice versa. This is due to differences in: — Selection rules
16. What does the term 'anharmonicity' imply for vibrational spectra? — Decreasing spacing between vibrational levels
17. What experimental technique is used to measure rotational spectra? — Microwave Spectroscopy
18. Which of the following is a common source used in Raman spectroscopy? — Argon ion laser
19. Which type of molecules can exhibit pure rotational spectra? — All of the above
20. Rayleigh scattering refers to: — Elastic scattering with no frequency change
21. Stokes lines in Raman spectra correspond to: — Inelastically scattered photons with lower energy than incident photons
22. Anti-Stokes lines in Raman spectra correspond to: — Inelastically scattered photons with higher energy than incident photons
23. For a linear molecule, a vibrational mode that causes a change in polarizability parallel to the molecular axis will be: — IR inactive and Raman active
24. What is the main advantage of Raman spectroscopy over IR spectroscopy for certain applications? — It can study homonuclear diatomic molecules
25. How does centrifugal distortion affect the rotational energy levels? — It makes the energy levels less closely spaced
26. For a molecule to exhibit a pure rotational spectrum, what must be true about its dipole moment? — It must be non-zero
27. What is the primary region of the electromagnetic spectrum for vibrational spectroscopy? — Far-infrared
28. What is the experimental technique used for studying vibrational spectra? — Infrared (IR) Spectroscopy
29. Which statement best describes the relationship between IR and Raman activity for vibrational modes in linear molecules? — IR and Raman activity are often complementary, with some modes active in one but not the other.
30. Which type of molecules can exhibit vibrational Raman spectra? — Only molecules with a changing polarizability
31. In rotation–vibration spectra of linear molecules, the P and R branches are generally observed when the vibrational mode is: — Parallel to the molecular axis
32. The Q branch in rotation–vibration spectra is typically observed for vibrational modes that are: — Perpendicular to the molecular axis in linear molecules
33. For a vibrational mode to be IR active, what must change during the vibration? — Dipole moment
34. What is the classical theory of Raman scattering based on? — Polarizability theory
35. In rotation–vibration spectra, what is observed for diatomic molecules? — A series of lines (a band) with fine structure due to rotation
36. What is the effect of increasing temperature on the intensity of Raman spectra? — Stokes line intensity decreases, Anti-Stokes line intensity increases.
37. Which of the following is NOT a type of Raman scattering? — Rayleigh scattering
38. The intensity of Raman scattering is generally: — Weaker than IR absorption
39. What is the Q branch in a rotation–vibration spectrum? — The branch where ΔJ = 0
40. The frequency shift in Raman scattering is related to: — The vibrational or rotational energy levels of the molecule
41. In the context of Raman scattering, what is polarizability? — The ability of a molecule's electron cloud to be distorted by an electric field
42. The spacing between lines in the P and R branches of a rotation–vibration spectrum is approximately equal to: — Twice the rotational constant B
43. What does the term 'centrifugal distortion' refer to in non-rigid rotor models? — The tendency of bonds to lengthen at higher rotational speeds
44. What is the role of the spectrograph in Raman spectroscopy? — To disperse the scattered light by frequency
45. What type of electromagnetic radiation is primarily used to study rotational spectra? — Microwave radiation
46. What is the selection rule for rotational transitions in a rigid rotor? — ΔJ = ±1
47. The selection rules for rotational Raman spectra involve changes in the rotational quantum number J by: — ΔJ = ±2
48. What is the selection rule for vibrational transitions in the harmonic oscillator approximation? — Δv = ±1
49. The frequency of a vibrational transition in a diatomic molecule is approximately given by: — ω = sqrt(k/μ)
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