Atomic and Molecular Physics MCQs Question and Answer in Engineering Physics Page-7 section-1

61.
The vibrational spectrum of a molecule exhibits a strong line with P and R branches at a frequency $${\nu _1}$$ and a weaker line at a frequency $${\nu _2}$$ . The frequency $${\nu _3}$$ is not shown up. Its vibrational Raman spectrum shows a strongly polarized line at frequency $${\nu _3}$$ and no feature at $${\nu _1}$$ and $${\nu _2}$$ .
Which of the following statements is correct?

A. The molecule could be linear

B. The molecule lacks a centre of inversion

C. $${\nu _1}$$ arises from a symmetric stretching mode

D. $${\nu _3}$$ arises from a bending mode

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62.
The short wavelength, cut-off of the continuous X-ray spectrum from a nickel target is 0.0825 nm. The voltage required to.be applied to an X-ray tube is

A. 0.15 kV

B. 1.5 kV

C. 15 kV

D. 150 kV

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63.
The allowed rotational energy levels of a rigid hetero-nuclear diatomic molecule are expressed as ε_J = BJ (J + 1), where B is the rotational constant and J is a rotational quantum number.
In a system of such diatomic molecules of reduced mass μ, some of the atoms of one element are replaced by a heavier isotope, such that the reduced mass is changed to 1.05μ. In the rotational spectrum of the system, the shift in the spectral line, corresponding to a transition J = 4 → J = 5, is

A. 0.475 B

B. 0.50 B

C. 0.95 B

D. 1.0 B

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64.
The degeneracies of the J-states arising from the ³p term with spin-orbit interaction are

A. 1, 3, 5

B. 1, 2, 3

C. 3, 5, 7

D. 2, 6, 10

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65.
The sodium doublet lines are due to transitions from ²p_3/2 and ²p_1/2 levels to ²s_1/2 level. On application of a weak magnetic field, the total number of allowed transitions becomes

A. 4

B. 6

C. 8

D. 10

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66.
In hyperfine interaction, there is coupling between the electron angular momentum $$\overrightarrow {\bf{J}} $$ and nuclear angular momentum $$\overrightarrow {\bf{I}} $$, forming resultant angular momentum $$\overrightarrow {\bf{F}} $$. The selection rules for the corresponding quantum number F in hyperfine transitions are

A. ΔF = ±2 only

B. ΔF = ±1 only

C. ΔF = 0, ±1

D. ΔF = ±1, ±2

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67.
The hyperfine splitting of the spectral lines of an atom is due to

A. the coupling between the spins of two or more electrons

B. the coupling between the spins and the orbital angular momentum of the electrons

C. the coupling between the electron spin and the nuclear spin

D. the effect of external electromagnetic fields

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68.
Three consecutive absorption lines at 64.275 cm^-1, 77.130 cm^-12 and 89.985 cm^-1 have been observed in a microwave spectrum for a linear rigid diatomic molecule. The moments of inertia $${I_A}$$ and $${I_B}$$ are ($${I_A}$$ is with respect to the bond axis passing through the centre of mass and $${I_B}$$ is with respect to an axis passing through the centre of mass and perpendicular to bond axis)

A. both equal to $$\frac{{{\hbar ^2}}}{{12.855\,hc}}$$ g-cm²

B. zero and $$\frac{{{\hbar ^2}}}{{12.855\,hc}}$$ g-cm²

C. both equal to $$\frac{{{\hbar ^2}}}{{6.427\,hc}}$$ g-cm²

D. zero and $$\frac{{{\hbar ^2}}}{{6.427\,hc}}$$ g-cm²

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69.
The L, S and J quantum numbers corresponding to the ground state electronic configuration of boron (Z = 5) are

A. L = 1, S = $$\frac{1}{2}$$, J = $$\frac{3}{2}$$

B. L = 1, S = $$\frac{1}{2}$$, J = $$\frac{1}{2}$$

C. L = 1, S = $$\frac{3}{2}$$, J = $$\frac{1}{2}$$

D. L = 0, S = $$\frac{3}{2}$$, J = $$\frac{3}{2}$$

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70.
The degeneracy of the spectral term ³f is

A. 7

B. 9

C. 15

D. 21

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Atomic and Molecular Physics MCQs Question and Answer in Engineering Physics

Answer & Solution

62. The short wavelength, cut-off of the continuous X-ray spectrum from a nickel target is 0.0825 nm. The voltage required to.be applied to an X-ray tube is

Answer & Solution

Answer & Solution

64. The degeneracies of the J-states arising from the 3p term with spin-orbit interaction are

Answer & Solution

65. The sodium doublet lines are due to transitions from 2p3/2 and 2p1/2 levels to 2s1/2 level. On application of a weak magnetic field, the total number of allowed transitions becomes

Answer & Solution

Answer & Solution

67. The hyperfine splitting of the spectral lines of an atom is due to

Answer & Solution

Answer & Solution

69. The L, S and J quantum numbers corresponding to the ground state electronic configuration of boron (Z = 5) are

Answer & Solution

70. The degeneracy of the spectral term 3f is

Answer & Solution

62.
The short wavelength, cut-off of the continuous X-ray spectrum from a nickel target is 0.0825 nm. The voltage required to.be applied to an X-ray tube is

64.
The degeneracies of the J-states arising from the ³p term with spin-orbit interaction are

65.
The sodium doublet lines are due to transitions from ²p_3/2 and ²p_1/2 levels to ²s_1/2 level. On application of a weak magnetic field, the total number of allowed transitions becomes

67.
The hyperfine splitting of the spectral lines of an atom is due to

69.
The L, S and J quantum numbers corresponding to the ground state electronic configuration of boron (Z = 5) are

70.
The degeneracy of the spectral term ³f is