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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. If the translational partition function for H$_2$ confined in a 1 L vessel at 300 K is $y \times 10^{27}$, then the value of $y$ is ______ (rounded off to one decimal place).
    (Given: Atomic mass (in amu): H = 1.008; 1 amu = $1.661 \times 10^{-27}$ kg; $h = 6.626 \times 10^{-34}$ J s; $k = 1.381 \times 10^{-23}$ J K$^{-1}$)
  2. 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)

  3. The rotational partition function of a diatomic molecule with energy levels corresponding to J = 0 and 1, is (where, $\epsilon$ is a constant)
  4. The molecular partition function of a system is given by
    $q(T) = (\frac{k_B T}{hc})^{\frac{3}{2}} (\frac{8\pi^2 mk_B T}{h^2})^{\frac{3}{2}}$, where the symbols have their usual meanings.
    The heat capacity at constant volume for this system is
  5. The molecular partition function for a system in which the energy levels are equispaced by $ε$, is
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