Life of Metastable Mercury and Evidence for a Long-Lived Metastable Vibrating Nitrogen Molecule

Curves showing the rate of decay of the metastable $2^3{P}_0$ state of mercury atom in a quartz resonance cell, containing carefully purified nitrogen at room temperature, are not accurately exponential. The rate of decay in the neighborhood of 4×${10}^{-4\mathrm{}}$ sec. after termination of the optical excitation, is more rapid than later. A high concentration of nitrogen molecules excited to the first and second vibrational states of the zero electronic state might be expected, due to collisions of the second kind between normal nitrogen molecules and mercury atoms in the $2^3{P}_1$ or $2^3{P}_2$ states. It is assumed that in addition to diffusion and dissipative impacts with unexcited nitrogen, the decay of the number of metastable mercury atoms may be influenced by dissipative impacts with these excited nitrogen molecules whose number decreases with time by diffusion and by dissipative impacts. An equation for the number of metastable mercury atoms is then obtained of the form $N=N_0\exp [-\alpha t+A(e^{-\beta t}-1\left)\right]$. Evaluation of the constants from experimental data gives the following: For excited vibrating metastable nitrogen molecule, maximum observed life 0.52×${10}^{-3\mathrm{}}$ sec.; natural life, infinite; distance between centers at impact, 0.85×${10}^{-8\mathrm{}}$ cm; probability of dissipative impact, 80×${10}^{-6\mathrm{}}$; diffusion coefficient 2.4 g · ${\mathrm{cm}}^{-2\mathrm{}}$ · ${\sec }^{-1\mathrm{}}$ · ${\mathrm{dyne}}^{-1\mathrm{}}$. For the metastable mercury atom, maximum observed life, 2.54×${10}^{-3\mathrm{}}$ sec.; natural life, infinite; distance between centers at impact, 3.2×${10}^{-8\mathrm{}}$ cm; probability of dissipative impact, 3.3×${10}^{-6\mathrm{}}$; diffusion coefficient, 0.129 g · ${\mathrm{cm}}^{-2\mathrm{}}$ · ${\sec .\mathrm{}}^{-1\mathrm{}}$ · ${\mathrm{dyne}}^{-1\mathrm{}}$.