The reduced mass, $\mu$, is given by the formula:
$$\mu = \frac{m_1 \cdot m_2}{m_1 + m_2}$$
where $m_1$ and $m_2$ are the masses of the two atoms involved in the bond. In this case, $m_1$ is the mass of hydrogen (1 amu) and $m_2$ is the mass of chlorine (35 amu).
Show more…