Knowledge Bank

The emission spectra of TiCl and ZrCl have been observed in the $1800-13500cm-1$ region using a Fourier transform spectrometer. The molecules were excited in a microwave discharge through flowing mixtures of $TiCl4$ or $ZrCl4$ and helium. The TiCl bands observed in the $11000-13500cm-1$ region have been assigned to a new $[12.8]2\Phi -a2\Phi$ electronic transition with the 0-0 bands of the $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Phi 5/2-2\Phi 5/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Phi 7/2-2\Phi 7/2$ subbands near 12733.7 and $12791.5cm-1$, respectively. For ZrCl, numerous bands observed in the $6700-12000cm-1$ region have been classified into two electronic transitions, $[7.3]2\Delta -a2\Phi$ and $[9.4]2\Phi -a2\Phi$. Five new bands observed in the $6700-7400cm-1$ region have been assigned as $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 3/2-2\Phi 5/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta 5/2-2\Phi 7/2$ subbands of a new electronic transition, $[7.3]2\Delta -a2\Phi$. The two subbands of the $[9.4]2\Phi -a2\Phi$ transition were previously observed by Phillips $etal.a$, who tentatively labeled them as $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 1/2-2\Pi 1/2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 3/2-2\Pi 3/2$ subbands. A number of new bands involving higher vibrational levels have been identified in these two subbands. Rotational analyses of several bands of TiCl and ZrCl have been obtained and spectroscopic constants for the observed doublet states have been extracted. The assignment of the observed electronic states will be discussed in light of recent theoretical calculations.