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Question

At temperature T, the canonical partition function of a harmonic oscillator with fundamental frequency ($\nu$) is given by
$q_{vib} (T) = \frac{e^{-h\nu/2k_BT}}{1-e^{-h\nu/k_BT}}$
For $\frac{h\nu}{k_BT} = 3$, the probability of finding the harmonic oscillator in its ground vibrational state is ____________ (Up to two decimal places)

Given

Canonical partition function of harmonic oscillator:
$q_{vib}(T) = \dfrac{e^{-h\nu/2k_BT}}{1 - e^{-h\nu/k_BT}}$

Given ratio: $\dfrac{h\nu}{k_BT} = 3$

Step 1: Write expression for ground state probability
The probability of finding the oscillator in the ground state is
$P_0 = \dfrac{e^{-h\nu/2k_BT}}{q_{vib}}$

Step 2: Substitute $q_{vib}$ into $P_0$
$P_0 = \dfrac{e^{-h\nu/2k_BT}}{\dfrac{e^{-h\nu/2k_BT}}{1 - e^{-h\nu/k_BT}}}$

This simplifies to
$P_0 = 1 - e^{-h\nu/k_BT}$

Step 3: Substitute numerical value
Given $\dfrac{h\nu}{k_BT} = 3$

$P_0 = 1 - e^{-3}$

$P_0 = 1 - 0.0498 = 0.9502$

Final Answer
$\boxed{0.95}$

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Important Questions from Partition Functions and Their Relation

  1. Six distinguishable particles are distributed over 3 non‐degenerate levels, of energies 0, ε and 2ε. The most probable value for the total energy is

  2. The partition function for a gas is given by

    Q(N, V, T) = \(\frac{1}{N!}\left(\frac{2\pi m}{h^2\beta}\right)^{3N/2}\) (v - Nb)N\(\frac{\beta aN^2}{V}\)

    The internal energy of the gas is

  3. A three-state system with energies E = −ε0, 0, +ε0 is in a thermal equilibrium at a temperature T. If β ε0 = x, the probability of finding the system with energy E = 0 is [recall, cosh x = \(\frac{1}{2}\)(ex + e−x)]

  4. The translational, vibrational, and rotational molecular partition functions for a system containing ideal diatomic gas molecules in the canonical ensemble (N, V, T) are written as, $q_{trans}$, $q_{vib}$, and $q_{rot}$, respectively. The option that correctly defines their thermodynamic variable(s) dependency is

  5. If $q_t$ and $Q_{t,m}$ are the molecular and molar translational partition functions of $X_2$, respectively, then $ln(Q_{t,m})$ = 
    (N is the Avogadro number)

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