## DIRECT OBSERVATION OF THE $a^{3}\Pi(\Omega = 1, \nu=0, 1, 2)$ AND $A'^{1}\Pi(\nu = 0, 1, 2)$ STATES OF BaO

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Ohio State University##### Abstract:

Using a single tunable dye laser, emission into the $a^{3}\Pi$ and $ A^{\prime}^{1}\Pi$ states of BaO has been observed in an isotopically selective optical-optical double resonance (OODR) experiment involving a real intermediate level. Absorption in the 6240 {\AA} region of the $A^{1}\Sigma^{+} - X^{1}\Sigma^{+} $system [(0,1) band] is followed by absorption from the $A^{1}\Sigma^{+} (\nu = 0)$ to a highly excited state (denoted $\nu^{*}$) which has predominate $^{1}\Sigma^{+}$ character. Emission from $\nu^{*} \rightarrow X^{1}\Sigma^{+}$ and $\nu^{*} \rightarrow$, $A^{1}\Sigma^{+}$ was also observed as welt as both $A^{1}\Sigma^{+} \rightarrow X^{1}\Sigma^{+}$ single resonance and cascade fluorescence. The electronic transition moment for $\nu^{*} \rightarrow a^{3}\Pi$ emission is due to spin-orbit mixing of $a^{3}\Pi$ and $A^{\prime}^{1}\Pi$, hence only $\Omega = 1$ of $a^{3}\Pi$ is observed. Intensities observed in $\nu^{*} \rightarrow a^{3}\Pi$ and $\nu^{*} \rightarrow A^{\prime}^{1}\Pi$ emission deviated from the expected 1:2:1 ratio for P, Q, and R branches, respectively. Four strong OODR lines were observed plus collision-induced satellites due to rotational relaxation in the $A^{1}\Sigma^{+}$ state. The tentative assignments $[(J_{A} \leftarrow J_{X}), (J_* \leftarrow J_{A})$ for the strong sequential excitation lines are R(48), P(49); R(32), R(33) P(29), P(78); and P(18), R(17). Preliminary values for $B_{\nu *}$ and the energy of $\nu^{*} (J^{*} = 0)$ relative to $X^{1}\Sigma^{+} (\nu = 0, J = 0)$ have been calculated giving $B_{\nu*}= 0.240 cm^{-1}$ and $E_{\nu*} = 32 \ \ 750 \ \mbox{ cm}^{-1}$.

##### Description:

This work was supported by the National Science Foundation and the Air Force Office of Scientific Research.

Author Institution: Massachusetts Institute of Technology, Cambridge

Author Institution: Massachusetts Institute of Technology, Cambridge

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article##### Other Identifiers:

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