Resonances in photoabsorption: Predissociation line shapes in the 3pπD $^1\Pi _u^+ \leftarrow X^1\Sigma _g^+$Πu+1←X1Σg+ system in H2

Abstract

The predissociation of the 3pπD¹Π(u)⁺, v ≥ 3, N = 2, and N = 3 levels of diatomic hydrogen is calculated by ab initio multichannel quantum defect theory combined with a R-matrix type approach that accounts for interfering predissociation and autoionization. The theory yields absorption line widths and shapes that are in good agreement with those observed in the high-resolution synchrotron vacuum-ultraviolet absorption spectra obtained by Dickenson et al. [J. Chem. Phys. 133, 144317 (2010)] at the DESIRS beamline of the SOLEIL synchrotron. The theory predicts further that many of the D state resonances with v ⩾ 6 exhibit a complex fine structure which cannot be modeled by the Fano profile formula and which has not yet been observed experimentally.

Absorption, autoionization, and predissociation in molecular hydrogen: High-resolution spectroscopy and multichannel quantum defect theory

“…In the present work, as in previous related work, 27 the electronic quantum defect matrix is effectively reduced to a single element, µ (Λ) (R) for Λ = 0 and 1, referring to the ion core ground state X + 2 Σ + g and corresponding to ℓ = ℓ ′ = 1. Consequently, the indices Λ + and ℓ may be dropped in Eq.…”

“…22,23,27,[33][34][35] An R-matrix type procedure is introduced in order to include dissociation channels along with the ionization channels. In a first step the integration range of the ion core vibrational wavefunctions χ(R) is limited to a finite rather small value, R c , which plays the role of the vibrational core boundary in addition to the electronic core boundary r c which appears in Eq.…”

“…The two quantum defect functions and their linear and quadratic energy dependences in the range up to threshold have been extracted in Ref. 27 from the best existing ab initio singlet ungerade Born-Oppenheimer potential energy curves [28][29][30] by use of the single-closed-channel clamped-nuclei version of the boundary condition, Eq. (3).…”

Isotope dependence of thec3Πu−b3Σ${}_{u}^{+}$ andD1Π${}_{u}^{+}$−B′1Σ${}_{u}^{+}$ predissociation rates of molecular hydrogen

“…The observed profile is usually a convolution of the predissociation, Doppler and instrumental profiles. While the predissociation profile is normally represented by the Fano line shape formula, Mezei et al (2014) has suggested that the formula cannot accurately represent the resonant profile for the v6 levels of H 2 . Each Fano profile is described by its center frequency, width (Γ) and asymmetry (q) parameters.…”

“…The D u 1 P + -B u 1 S + coupling is at least another order of magnitude weaker than the D u 1 P + -C u 1 P + coupling. The MQDT method, in principle, automatically includes the interaction of the D u 1 P + state with other npσ and npπ Rydberg states (Glass-Maujean et al 2012c as well as the interference between predissociation and autoionization (Mezei et al 2014). However, all investigations have confirmed that the predissociation of the D u 1 P + state is dominated by the B¢ u 1 S + continuum.…”