ESR matrix-isolation apparatus used for trapping the H2 +, HD+, and D2 + radical cations utilizing x-ray irradiation. Without the 77 K copper heat shield, the matrix isolation of hydrogen molecular ions was found to be impossible. Not pictured is the external magnet used for obtaining the ESR spectra and the vacuum-sealed quartz window on the matrix chamber through which x-irradiation and photolysis were conducted.
Summary of all H2 +, HD+, and D2 + ESR transitions in 2 K neon matrices with respect to hydrogen and deuterium atomic transitions pictured at the bottom of the figure. Tall lines indicate the perpendicular transitions and shorter lines indicate parallel transitions. Near ge, the perpendicular and parallel transitions overlap.
The observed (top) and simulated (lower) spectra of H2 + ESR transitions in 2 K neon matrices are presented. Although a triplet hyperfine splitting pattern is expected, the central lines are observed as two distinct transitions due to second-order effects. Parallel and perpendicular components are clearly observed for J = 1 transitions. In order to observe the broader MJ = ±1 transitions, the instrumental amplification and modulation had to be increased significantly.
The ESR spectra of H2 + (a) before and (b) after visible light photolysis are presented. Only the MJ = ±1 perpendicular components are pictured. Five-minutes of visible light photolysis of the neon matrix helps distinguish free neutral radicals from free ion radicals. A 60% reduction in peak intensity is observed for all H2 + transitions.
The observed (top) and simulated (lower) spectra of D2 + ESR transitions in 2 K neon matrices are presented. The first, second, fourth, and fifth peaks of the D2 + quintet are shown above. The perpendicular components labeled in the simulated spectrum were readily observed, but peak broadening and overlap with D4 + absorptions (indicated by A and B) make the parallel components hard to identify. The center peaks of D2 + could not be observed due to impurities in the matrix and are not pictured here.
The observed (top) and simulated (lower) spectra of HD+ ESR transitions in 2 K neon matrices are presented. Ten of the twelve ESR features for HD+ are observable. The letter A and D indicate the beginning of the H2D2 + hyperfine structure, which obscures the outer-most parallel components of the HD+ spectrum. B and C indicate the strong D atom signal.
Observed ESR line positions (Gauss) for H2 + in neon matrices at 2 K.a
Observed ESR line positions (Gauss) for D2 + in neon matrices at 2 K.a
Calculated ESR line positions (Gauss) for HD+ in neon matrices at 2 K.a
Observed magnetic parameters (MHz) for H2 +, D2 +, and HD+ in neon matrices at 2 K.a
Comparison of observed magnetic parameters (MHz) for H2 + in 2 K neon matrix with previous experimental and theoretical results.
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