Knowledge Bank

The high resolution emission spectrum of $\mathrm{<mrow\; data-mjx-texclass="ORD">204</mrow>}Hg2$ near $22000cm-1$ has been measured and eight bands analysed. The band show P-, Q-, and R-branches with the Q-branches lines having greater intensity than either the P- or R-branches lines. The analysed transitions range from $J\prime =15$ to $J\prime =245$ and it has been shown that the Q-branches transitions involve only even J values while the P- and R-branch transitions involve only odd $J\prime$ values. The vibrational numbering has not yet been ascertained by isotopic substitution but the data a re consistent with the vibrational assignments of Takeyama (1). The band system must be due to either a $0g+-1u$ or $0u--1g$ electronic transition. Typical bond distance are 2.700{\AA} for the upper state and 2.602{\AA} for the lower state.