Knowledge Bank

A Lyman-alpha lamp excites hydrogen atoms in a weak d.c. discharge to the 2p state, and the fluorescence spectrum is observed at right angles with a 1 meter vacuum u.v. spectrometer and lock-in detection. The Lyman bands of $H2$($B1\Sigma u+$ $v\prime \le 2\to X1\Sigma g+$) are seen, suggesting the excitation transfer process $H8$(2p)$+H2$(X, v = 2) = $H+H2\mathrm{<mrow\; data-mjx-texclass="ORD">8</mrow>}$(B, $v\le 2$), where the initial vibrational excitation in $H8$(X), obtained in the discharge, is necessary for energetic reasons. A possible mechanism for excitation transfer involving an intermediate compound state of $H2\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ is discussed.