Atomic And Molecular Physics — Part 2 MCQs with Explanations

$$\left( {\overline v - {E_{ex}}} \right)$$ is the correct answer to “A vibrational-electronic spectrum of homonuclear binary molecules, involving electronic ground state ε'' and excited ε', exhibits a continuum at $$\overline v $$ cm -1 . If the total energy of the dissociated atoms in the excited state exceeds the total energy of the dissociated atoms in the ground state by E ex cm -1 , then dissociation energy of the molecule in the ground state is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

ΔL = 0, ±1; ΔS = 0; Δ$$l$$ = ±1 is the correct answer to “For a multi-electron atom $$l$$, L and S specify the one electron orbital angular momentum, total orbital angular momentum and total spin angular momentum respectively. The selection rules for electric dipole transition between the two electronic energy levels, specified by $$l$$, L and S are”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

allowed if the two states have opposite parities is the correct answer to “Two states of an atom have definite parities. An electric dipole transition between these states is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

Ng ≈ Ne ≈ N/2 is the correct answer to “A collection of N atoms is exposed to a strong resonant electromagnetic radiation with N g atoms in the ground state and N atoms in the excited state, such that N g + N e = N. This collection of two-level atoms will have the following population distribution”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

4f3/2 is the correct answer to “The last two terms of the electronic configuration of manganese (Mn) atom is 3d 5 4s 2 . The term factor of Mn 4+ ion is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

L = 0, S = 1 and L = 2, S = 1 is the correct answer to “Deuteron in its ground state has a total angular momentum J = 1 and a positive parity. The corresponding orbital angular momentum L and spin angular momentum S combinations are”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

$$\frac{{\omega \lambda }}{{2\pi }},\,\frac{{\Delta \omega {\lambda ^2}}}{{2\pi \Delta \lambda }}$$ is the correct answer to “Two monochromatic waves having frequencies $$\omega $$ and $$\omega + \Delta \omega \left( {\Delta \omega \ll \omega } \right)$$ and corresponding wavelengths $$\lambda $$ and $$\lambda - \Delta \lambda \left( {\Delta \lambda \ll \lambda } \right)$$ of same polarization, travelling along X-axis are superimposed on each other. The phase velocity and group velocity of the resultant wave are respectively given by”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

$${\nu _e}$$ - 10B, $${\nu _e}$$ - 14B is the correct answer to “A pure rotational Raman spectrum of a linear diatomic molecule is recorded using electromagnetic radiation of frequency $${\nu _e}$$ . The frequency of two consecutive Stokes lines are”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

$$\frac{{2I{k_B}T}}{{{\hbar ^2}}}$$ is the correct answer to “The rotational partition function for a diatomic molecule of moment of inertia $$I$$ at a temperature T is given by”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

P-2, Q-3, R-1 is the correct answer to “Match the typical spectra of stable molecules with the corresponding wave number range P. Electronic spectra 1. 10 6 cm -1 and above Q. Rotational spectra 2. 10 5 - 10 6 cm -1 R. Molecular dissociation 3. 10 0 - 10 2 cm -1”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

O-C-S would show absorption lines but not O-C-O is the correct answer to “The molecular spectra of two linear molecules O-C-O and O-C-S are recorded in the microwave region. Which one of the following statements is correct”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

pV4/3 = constant is the correct answer to “If the equation of state for a gas with internal energy U is pV = $$\frac{1}{3}$$U, then the equation for an adiabatic process is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

n = 4 → n = 2 is the correct answer to “The L β line of X-rays emitted from an atom with principal quantum numbers n = 1, 2, 3, . . . . . . . ., arises from the transition”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

2 → 0 is the correct answer to “Five energy levels of a system including the ground state are shown below. Their lifetimes and the allowed electric dipole transitions are also marked. Which one of the following transitions is the most suitable for a Continuous Wave (CW) laser”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

$$\frac{c}{{2L}}\frac{{\Delta \mu }}{{\mu \left( {\mu + \Delta \mu } \right)}}$$ is the correct answer to “When the refractive index $$\mu $$ of the active medium changes by $${\Delta \mu }$$ in a laser resonator of length L, the change in the spectral spacing between the longitudinal modes of the laser is (c is the speed of light in free space)”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

1s0, 3p0, 1, 2 and 1d2 is the correct answer to “The allowed states for He (2p 2 ) configuration are”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

Δ$$l$$ = ±1, Δm$$l$$ = 0, ±1 is the correct answer to “For an electron in hydrogen atom, the states are characterized by the usual quantum numbers n, $$l$$, m $$l$$ . The electric dipole transition between any two states requires that”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

P-1, Q-4, R-3, S-2 is the correct answer to “Match the following: P. Franck-Hertz experiment 1. Electronic excitation of molecules Q. Hartree-Fock method 2. Wave function of atoms R. Stern-Gerlach experiment 3. Spin angular momentum of atoms S. Franck-Condon principle 4. Energy levels in atoms”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

26 is the correct answer to “X-rays were produced using cobalt (Z = 27) as target. It was observed that the X-ray spectrum contained a strong K α line of wavelength 0.1785 nm an a weak K α line of wavelength 0.1930 nm. Then the weak K α line is due to an impurity whose atomic number is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

The molecule could be linear is the correct answer to “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”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

15 kV is the correct answer to “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”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

0.475 B is the correct answer to “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”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

1, 3, 5 is the correct answer to “The degeneracies of the J-states arising from the 3 p term with spin-orbit interaction are”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

10 is the correct answer to “The sodium doublet lines are due to transitions from 2 p 3/2 and 2 p 1/2 levels to 2 s 1/2 level. On application of a weak magnetic field, the total number of allowed transitions becomes”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

ΔF = 0, ±1 is the correct answer to “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”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

the coupling between the spins and the orbital angular momentum of the electrons is the correct answer to “The hyperfine splitting of the spectral lines of an atom is due to”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

zero and $$\frac{{{\hbar ^2}}}{{12.855\,hc}}$$ g-cm2 is the correct answer to “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)”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

L = 1, S = $$\frac{1}{2}$$, J = $$\frac{1}{2}$$ is the correct answer to “The L, S and J quantum numbers corresponding to the ground state electronic configuration of boron (Z = 5) are”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

9 is the correct answer to “The degeneracy of the spectral term 3 f is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

6 is the correct answer to “Assuming that the L-S coupling scheme is valid, the number of permitted transitions from 2 P 3/2 to 2 s 1/2 due to a weak magnetic field is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

4 and 6 lines respectively is the correct answer to “The D 1 and D 2 lines of Na(3 2 p 1/2 → 3 2 s 1/2 , 3 2 p 3/2 → 3 2 s 1/2 ) will split on the application of a weak magnetic field into”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

4 is the correct answer to “The NMR spectrum of ethanol (CH 3 CH 2 OH) comprises of three bunches of spectral lines. The number of spectral lines in the bunch corresponding to CH 2 group is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

7.8 × 10-46 is the correct answer to “In the microwave spectrum of identical rigid diatomic molecules, the separation between the spectral lines is recorded to be 0.7143 cm -1 . The moment of inertia of the molecule, in kg-m 2 is”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

infrared and microwave is the correct answer to “The typical wavelengths emitted by diatomic molecules in purely vibrational and purely rotational transitions are respectively in the region of”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

$$\frac{1}{V}$$ is the correct answer to “The target of an X-ray tube is subjected to an excitation voltage V. The wavelength of the emitted X-rays is proportional to”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.

$${\Gamma _{{l_1}{s_1}}},\,{\Gamma _{{l_2}{s_2}}} > {\Gamma _{{l_1}{l_2}}},\,{\Gamma _{{s_1}{s_2}}}$$ is the correct answer to “In a two-electron atomic system having orbital and spin angular momenta $${l_1}{l_2}$$ and $${s_1}{s_2}$$ respectively, the coupling strengths are defined as $${\Gamma _{{l_1}{l_2}}},\,{\Gamma _{{s_1}{s_2}}},\,{\Gamma _{{l_1}{s_1}}},\,{\Gamma _{{l_2}{s_2}}},\,{\Gamma _{{l_1}{l_2}}}$$ and $${\Gamma _{{l_2}{s_1}}}.$$ For the jj coupling. scheme to be applicable, the coupling strengths must satisfy the condition”. This question is standard in competitive examination syllabi for Atomic And Molecular Physics.