2025 Data (Information)

Data for: Controlling the Internal Excitation of H₃⁺ Produced in a Duoplasmatron Ion Source

Ivanov, Dmitry; Bu, Caixia; Hillenbrand, Pierre-Michel; Schury, Daniel; Urbain, X.; Savin, Daniel Wolf

We have explored a combination of two methods to control the internal excitation of H₃⁺ produced in a duoplasmatron ion source. The H₃⁺ was formed starting from a gas of H₂. The first control method varied the H₂ pressure in the ion source to collisionally relax any internally excited (H₃⁺)*. The second method added Ar to the source to chemically destroy (H₃⁺)* with internal excitation energies 𝘌ᵢₙₜ ⩾ 0.57 eV, using the endoergic reaction H₃⁺ + Ar → ArH⁺ + H₂. To infer the H₃⁺ internal temperature, 𝘛ᵢₙₜ, representative of internal excitation under the hypothesis of thermodynamic equilibrium, we used merged-beams rate coefficient measurements of the endoergic deuterating reaction H₃⁺ + D → H₂D⁺ + H₂ and a semi-empirical theoretical model. We found that using collisional relaxation alone, we could vary 𝘛ᵢₙₜ over the range ≈ 1300 − 2400 K. Combining collisional relaxation and chemical destruction, we reduced the minimum to 𝘛ᵢₙₜ ≈ 1130 K. Over this temperature range, the fraction of H₃⁺ where all vibrational modes are in their 𝘷 = 0 level varies from ≈ 0.88 at the lowest temperature to ≈ 0.44 at the highest temperature. This combination of cooling methods offers a potentially powerful means for studying reactive scattering processes as a function of the internal excitation of the H₃⁺.

Keywords: molecular beam sources and techniques, techniques for molecular physics, atomic and molecular collision processes and interactions, H₃⁺, internal excitation, collisional relaxation, chemical destruction