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Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: Two-dimensional resonance enhanced multiphoton ionization of HBr via singlet-, triplet-, Ω = 0 and 2 states
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Image of FIG. 1.
FIG. 1.

HBr energetics. Potential energy curves, asymptotic energies (right), photon excitations (red arrows; left) corresponding to two-photon resonance excitation to the F 1Δ2(v′ = 1) state and relative absorption intensity of the A-band (Ref. 33) (tilted to the left). Potential curves other than the repulsive states are derived from Fig. 1 in Ref. 18. Repulsive potentials (A, t and the a states) are derived from Fig. 1 in Ref. 34. Threshold energies are derived from atom energy levels.35

Image of FIG. 2.
FIG. 2.

1D-REMPI spectra for H+, 81Br+, and H81Br+ and J′ assignments for rotational peaks corresponding to two-photon resonance excitations to the F 1Δ2(v′ = 1), V 1Σ+(v′ = m + 7), H1Σ+ (v′ = 0), V 1Σ+(v′ = m + 8), and E 1Σ+ (v′ = 1) states. New, previously unreported spectrum in REMPI, assigned to two-photon resonance transition to the k 3Π0(v′ = 0) state is marked in figure (d). Three atomic lines due to (2 + 1) REMPI of Br are also marked (see Table VI).

Image of FIG. 3.
FIG. 3.

Rotational energy levels, derived from observed REMPI rotational peaks for the F 1Δ2(v′ = 1)(a), V 1Σ+(v′ = m+7)((a) and (b)), H 1Σ+ (v′ = 0)(b), V 1Σ+(v′ = m + 8)((a) and (b)) and E 1Σ+ (v′ = 1)(a) states. Observed level-to-level near-resonance interactions between F(1) and V(m + 7) and off-resonance interactions between the V(m + 7) and V(m + 8) ion-pair states and the E(1) and H(0) Rydberg states are indicated by broken lines. Strength and alterations in state mixings are indicated, roughly, by varying thickness of broken lines.

Image of FIG. 4.
FIG. 4.

HiBr: Spacings between rotational levels (ΔE J′, J′ − 1) as a function of J′ for F 1Δ2(v′ = 1)(a), E 1Σ+(v′ = 1)(a), V 1Σ+(v′ = m + 7)(a), H 1Σ+(v′ = 0)(b), and V 1Σ+(v′ = m + 8)(b). Dots connected by solid lines are derived from Q rotational lines. Broken lines are line fits for, J′ = 3–5 and 8 values for F(1), J′ = 1–3 values for E(1), J′ = 1–6 values for H(0), and J′ = 1–5 values for V(m + 8). The broken line for V(m + 7) joins the dots for J′ = 1 and 9 to guide the eye.

Image of FIG. 5.
FIG. 5.

Relative ion signal intensities, I( i Br+)/I(H i Br+) (i = 79, 81) vs. J′ derived from Q rotational lines of REMPI spectra due to two-photon resonance transitions to the Rydberg states F(1) (a), E(1)(c), and H(0)(d). (b) shows simulation for (a), assuming J′ level-to-level interactions between the F(1) and V(m + 7) states (black columns) for W12 = 0.68 cm−1, α = 1.26, and γ = 0.11 as well as calculated ratios for same W12, α = 2.67, and γ = 0 (white columns) (see text).

Image of FIG. 6.
FIG. 6.

Rotational line-widths vs. J′ derived from REMPI spectra for (a) F(1), P lines, H i Br+ (i = 79, 81), (b) F(1), Q lines, H i Br+, (c) F(1), S lines, H i Br+, (d) V(m + 7), Q lines, H+, (e) E(1), Q lines, H i Br+, (f) H(0), Q lines, H i Br+. The line-width derived for F(1), P line, J′ = 7 (a) is overestimated due to overlap of peaks P(J′ = 7) and O(J′ = 4) (see Fig. 2(a)). Due to very weak intensity and breadth of the V(m + 7), Q line, J′ = 5 peak line-width could not be determined (d).

Image of FIG. 7.
FIG. 7.

Semischematic figure, showing the H i Br energetics, state interactions, and transfers of relevance. Rotational and spin-orbit couplings are marked JL and SO, respectively. States marked G and R are gateway and repulsive states, respectively. States and couplings inside brackets are example cases believed to be of importance. Relative importance of couplings and transfers are indicated by different boldness of arrows. Quantum interference effects between states are indicated by arrows marked QI.


Generic image for table
Table I.

Typical equipment/condition parameters for REMPI experiments.

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Table II.

Rotational lines for H i Br (i = 79, 81), due to two-photon resonance transitions to the V 1Σ+(v′ = m + 7), V 1Σ+(v′ = m + 8), E 1Σ+(v′ = 1), F 1Δ2(v′ = 1), H 1Σ+(v′ = 0) and “New” (k 3Π0(v′ = 0)) states (see text).

Generic image for table
Table III.

Parameters derived from line-shift and intensity-ratio (I( i Br+)/I(H i Br+)) analysis of the F(1) ←← X system (see Figs. 4(a), 6(a), and 6(b))

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Table IV.

(Lower limit) lifetimes (ps) of rotational states (J′) derived from REMPI spectra line-widths (see text). The values were derived from Q lines of H i Br+ (i = 79, 81) signals for E(1), F(1), and H(0) but from Q lines of H+ signals for V(m + 7).

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Table V.

State couplings based on correlation diagrams from Ref. 31. Spin-orbit couplings are marked SO. Rotational couplings, L uncoupled and S-uncoupled, are marked JL and JS, respectively.

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Table VI.

(2 + 1) REMPI bromine atomic lines and closest HiBr rotational lines.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: Two-dimensional resonance enhanced multiphoton ionization of HBr via singlet-, triplet-, Ω = 0 and 2 states