Photo-assisted fragmentation spectroscopy of triatomic hydrogen

Article abstract of DOI:10.1016/0009-2614(88)87485-2

The R₀(0) line of the 3s²A′₁←2p²A″₂ transition of the H₃ radical has been observed in absorption by the new technique of photo-assisted fragmentation spectroscopy. A fast beam of metastable H₃ radicals produced by H₃⁺/K electron transfer is interacted with visible light from a dye laser. Optical absorption is detected by observing a decrease in parent peak intensity in the H₃⁺ neutralization-reionization mass spectrum, resulting from dissociation of the neutral molecule. Absorption line widths are observed to be instrumentally limited (≈ 0.05 cm^-1) as the upper state of the transition is spectroscopically long lived. Application of the technique to various second-row hypervalent hydride radicals is discussed.