Feshbach resonances of the H⁻₃ and D⁻₃ anions

Abstract

Based on a series of ab initio calculations two Feshbach resonances of the H ⁻ ₃ negative ion having λ(1 sa′₁)²(2sa′₁)²−μ(1sa′₁)²(2pa′′₂)²: ¹ A′₁ and (1sa′₁)²(2sa′₁)(2pa′′₂): ³ A′′₂ electronic structure and estimated lifetimes of more than 10⁻¹⁴ s are predicted. The potential energy surfaces of the Feshbach states are roughly parallel to those of the Rydberg states of neutral H ₃ and show minima located between the dissociative 2pE′ ground state surfaces and the lowest Rydberg states 2sA′₁ and 2pA′′₂ of H ₃. We have determined a number of vibrational levels of the non-rotating molecules H ⁻ ₃ and D ⁻ ₃ and we predict electron affinities for the mentioned two Rydberg states.

Keywords:

• H ₃/H ⁻ ₃, D ₃/D ⁻ ₃
• Feshbach resonance
• ab initio calculations
• potential energy surfaces
• vibrational levels
• excited state electron affinities

Acknowledgements

The authors thank the Ernst Miescher Foundation (Basel, Switzerland) for technical support.

Notes

^a For H ₃ the non-rotating (J = 0) vibration level with v ₁ = v ₂ = 0. is Pauli-forbidden.

^bwith respect to the minimum at −1.49892 a.u. for r _HH = 1.605 a _o .

^cwith respect to the minimum at −1.49665 a.u. for r _HH = 1.621 a _o .

^dwith respect to the minimum at −1.48382 a.u. for r _HH = 1.603 a _o .

^ewith respect to the minimum at −1.47822 a.u. for r _HH = 1.642 a _o .

^ffrom Ref. [32].

1. 2003 Wang et al. [11] reported to have observed H ⁻ ₃.

2. With a basis containing one set of f functions added on the H atoms we obtain −1.48357 a.u. and −1.47845 a.u., respectively.

3. An electronic copy of Ref. [30] can be obtained from the author.

4. Essential of course for the reduced symmetries C ₂ v and C _s , not for D _3h .

5. Neutralisation of the triplet Feshbach state by the dissociative third valence state ⁴ A′₂ can be ruled out because its PES is much higher in the reference region.