Fine Structure, Dipole Moment, and Perturbation Analysis of a 3Π CO

Theedio‐frequency spectrum of the ${\mathrm{a\hspace{0.17em}}}^3\Pi$ state of carbon monoxide from 5 to 1000 MHz has been measured in a molecular beam electric resonance spectrometer. Lambda doubling transitions in $\text{Ω=2,\hspace{0.17em}J=2–8,\hspace{0.17em}v=0–5}$ and several in $\text{Ω=1}$ have been measured to an accuracy of 1 kHz as a function of electric field. A simultaneous least squares fit to optical and radio‐frequency data on ${\mathrm{a\hspace{0.17em}}}^3\Pi$ determines a set of fine structure constants which reproduce the optical and radio‐frequency measurements within their respective experimental errors. The vibrational dependence of the constants which determine the lambda doubling in the ${\mathrm{a\hspace{0.17em}}}^3\Pi$ state is accounted for. $\text{v=4\hspace{0.17em}}\mathrm{and}\text{\hspace{0.17em}5}$ of ${\mathrm{a\hspace{0.17em}}}^3\Pi$ are perturbed by $\text{v=0\hspace{0.17em}}\mathrm{and}\text{\hspace{0.17em}1}$ of ${\mathrm{a\prime \hspace{0.17em}}}^3{\Sigma }^{+}$ , respectively. Analysis of the radio‐frequency lambda doublings and perturbed optical spectra determines two vibration‐independent matrix elements of the Hamiltonian off diagonal in electronic state which describe the ${\mathrm{a\hspace{0.17em}}}^3{\mathrm{\Pi ‐a\prime \hspace{0.17em}}}^3{\Sigma }^{+}$ interaction, ${\mathrm{〈\; a\hspace{0.17em}}}^3{\mathrm{\Pi ,\hspace{0.17em}v|AL}}_{+}{\text{/2|a′\hspace{0.17em}}}^3{\Sigma }^{+}\text{,\hspace{0.17em}v′〉/〈 v|v′〉=0.74± 0.15\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ and ${\mathrm{〈\; a\hspace{0.17em}}}^3{\mathrm{\Pi ,\hspace{0.17em}v|BL}}_{+}{\mathrm{|a\prime \hspace{0.17em}}}^3{\Sigma }^{+}\text{,\hspace{0.17em}v′〉/〈 v|B|v′〉=0.154± 0.005}$ unitless. Extensive Stark effect measurements determine the dependence of the dipole moment of ${\mathrm{a\hspace{0.17em}}}^3\Pi$ on v, J, and Ω. Analysis of the $\text{v=4\hspace{0.17em}}\mathrm{and}\text{\hspace{0.17em}5}$ Stark effect data determines the transition moment between ${\mathrm{a\hspace{0.17em}}}^3\Pi$ and ${\mathrm{a\prime \hspace{0.17em}}}^3{\Sigma }^{+}{\mathrm{,\hspace{0.17em}〈\; a\hspace{0.17em}}}^3{\mathrm{\Pi \; |\hspace{0.17em}|\mu |\hspace{0.17em}|a\prime \hspace{0.17em}}}^3{\Sigma }^{+}\text{〉=0.504± 0.01\hspace{0.17em}}\mathrm{D}$ , and the dipole moment of the ${\mathrm{a\prime \hspace{0.17em}}}^3{\Sigma }^{+}$ state, $\text{μ=−1.06± 0.2\hspace{0.17em}}\mathrm{D}\mathrm{\hspace{0.17em}(}{\mathrm{C}}^{-}{\mathrm{O}}^{+})$ .