Laser spectroscopy in a pulsed jet of AlH: Ionization‐detected ultraviolet absorption spectra of the transitions <i>C</i> <sup>1</sup>Σ<sup>+</sup>–<i>X</i> <sup>1</sup>Σ<sup>+</sup> and <i>b</i> <sup>3</sup>Σ<sup>−</sup>–<i>X</i> <sup>1</sup>Σ<sup>+</sup>
作者:Yi Fei Zhu、Rana Shehadeh、Edward R. Grant
DOI:10.1063/1.463192
日期:1992.7.15
We report the production of radical transients AlH and AlD in a filament-source pulsed free-jet expansion. In this source, hydrogen gas from a pulsed valve passes over hot tungsten filament wrapped by a layer of aluminum wire. Liquid aluminum wetting the filament reacts rapidly to form (AlH3)x oligomer. Depending on filament temperature, either AlH or AlH2 sublimes from this oligomeric coating to be entrained in subsequent pulses of H2. The source has been characterized by laser induced fluorescence and ionization-detected one-photon absorption with time-of-flight mass resolution. Laser-induced fluorescence measurements focus on the well-known A–X transition of AlH. Higher energy ionization-detected absorption spectra resolve the C 1Σ+–X 1Σ+ transition in AlH and AlD, and for the first time the forbidden transition, b 3Σ−–X 1Σ+, in AlH. Spectroscopic constants determined from an analysis of bands assigned to v=0 and v=1 of the b 3Σ− state are Te = 40 524 cm−1, Be = 7.0675 cm−1, De = 6.1 × 10−5 cm−1, αe = 0.637 cm−1, βe = 6.38× 10−4, and γe = 1.5725, with v=0 spin–orbit and spin–rotation coupling parameters λ0=0.29 cm−1, and γ0=0.03 cm−1, inducing structure in a transition that appears to be predominantly parallel. For v=1, spin–orbit coupling is much stronger, and rotational branch intensities suggest interference, indicating that both parallel and perpendicular components of the transition moment contribute to the total oscillator strength. Results for the C–X (0–0) transitions give B0 = 6.3869 cm−1 and D0 = 5.329 × 10−4 with T0 = 44 594.05 cm−1 for the AlH C state, and B0 = 3.3457 cm−1 and D0 = 1.380× 10−4 cm−1 with T0 = 44 631.09 cm−1 for the AlD C state.