Measurements on thewΔu1→aΠg1Transition in Molecular Nitrogen

A new emission system of molecular nitrogen near 3.65 μ has been observed. It arises from transitions in the 0→0 band of $w{}_{}{}^1{}_{}{}^{}\Delta _u^{}{}_{}{}^{}\to a{}_{}{}^1{}_{}{}^{}\Pi _g^{}{}_{}{}^{}$. The results permit a more direct determination of the electronic term value of $w{}_{}{}^1{}_{}{}^{}\Delta _u^{}{}_{}{}^{}: T_{00}\left(w{}_{}{}^1{}_{}{}^{}\Delta _u^{}{}_{}{}^{}\right)=71,698.44\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$. A value of the rotational constant difference $B_{0c}-B_{0d}=(1.0\mathrm{}\pm 0.3)\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$ has been found for the $v=0\mathrm{}$ level of $a{}_{}{}^1{}_{}{}^{}\Pi _g^{}{}_{}{}^{}$.