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Molecular Physics
An International Journal at the Interface Between Chemistry and Physics
Volume 119, 2021 - Issue 17-18: The Beauty of Chemical Reaction Kinetics: A Festschrift in Honour of Jürgen Troe
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Jürgen Troe Special Issue

Beyond the helium buffer: 12C−2 rotational cooling in cold traps with H2 as a partner gas: interaction forces and quantum dynamics

Barry Manta Department of Chemistry, University College London, London, UKORCID Iconhttps://orcid.org/0000-0002-3116-5364View further author information
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Jan Franzb Faculty of Applied Physics and Mathematics, Institute of Physics and Computer Science, Gdańsk University of Technology, Gdańsk, PolandORCID Iconhttps://orcid.org/0000-0002-4279-0608View further author information
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Roland Westerc Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, AustriaORCID Iconhttps://orcid.org/0000-0001-7935-6066View further author information
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F. A. Gianturcoc Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Innsbruck, AustriaCorrespondence[email protected]
ORCID Iconhttps://orcid.org/0000-0002-8043-9042View further author information
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Article: e1938267 | Received 28 Mar 2021, Accepted 27 May 2021, Published online: 10 Jun 2021

Figures & data

Figure 1. Definition of the body-fixed coordinates system.

Figure 1. Definition of the body-fixed coordinates system.

Figure 2. Cuts of C2−/H2 PES along the radial coordinate RCH for the three H2 orientations used in the present calculations, plus its average value. Different different values of θ are shown.

Figure 2. Cuts of C2−/H2 PES along the radial coordinate RCH for the three H2 orientations used in the present calculations, plus its average value. Different different values of θ are shown.

Figure 3. Contour plots of C2−-H2 averaged 2D-PES (left) and full 2D-PES for the C2−-Ar(right).The levels of energy contours are given in units of (hc cm−1).

Figure 3. Contour plots of C2−-H2 averaged 2D-PES (left) and full 2D-PES for the C2−-Ar(right).The levels of energy contours are given in units of (hc cm−1).

Figure 4. Radial coefficients of the expansion given by Equation (Equation2) for C2− interacting with H2 (solid lines) and Ar (dashed lines). Only the first three, most important radial functions are shown.

Figure 4. Radial coefficients of the expansion given by Equation (Equation2(2) Vav(R,θ)=∑λλmaxVλ(R)Pλ(cos⁡θ)(2) ) for C2− interacting with H2 (solid lines) and Ar (dashed lines). Only the first three, most important radial functions are shown.

Figure 5. Rotationally inelastic scattering cross-sections for C2− colliding with p-H2($j= 0$) (solid lines) and He (dashed lines) for excitation (top panels) and quenching (bottom panels).

Figure 5. Rotationally inelastic scattering cross-sections for C2− colliding with p-H2($j= 0$) (solid lines) and He (dashed lines) for excitation (top panels) and quenching (bottom panels).

Figure 6. Rotationally inelastic scattering cross-sections for pseudo-singlet C2− colliding with para-H2(j = 0) (solid lines) and with Ar (dashed lines) for excitation (top panels) and quenching (bottom panels).

Figure 6. Rotationally inelastic scattering cross-sections for pseudo-singlet C2− colliding with para-H2(j = 0) (solid lines) and with Ar (dashed lines) for excitation (top panels) and quenching (bottom panels).

Figure 7. Examples of rotationally inelastic rate constants kj→j′(T) for for C2− colliding with H2 and He. Rate constants obtained by multiplying those of He by f1 and f2 factors are also shown.

Figure 7. Examples of rotationally inelastic rate constants kj→j′(T) for for C2− colliding with H2 and He. Rate constants obtained by multiplying those of He by f1 and f2 factors are also shown.

Figure 8. Rotationally inelastic rate constants kN→N′(T) for corresponding transitions of Figure  for C2− colliding with p-H2(j = 0) (solid lines) and Ar (dashed lines).

Figure 8. Rotationally inelastic rate constants kN→N′(T) for corresponding transitions of Figure 6 for C2− colliding with p-H2(j = 0) (solid lines) and Ar (dashed lines).

Figure 9. Computed quenching functions for C2− interacting with p-H2(j = 0) (solid lines) and He (dashed lines) as function of the expected range of trap temperatures. Two different initial rotational states are shown as examples for both systems. See main text for further comments.

Figure 9. Computed quenching functions for C2− interacting with p-H2(j = 0) (solid lines) and He (dashed lines) as function of the expected range of trap temperatures. Two different initial rotational states are shown as examples for both systems. See main text for further comments.

Figure 10. Thermalisation of C2− rotational N states during collisions with He, Ar and H2 at 20 K. Initial populations are taken from a Boltzmann distribution at 100 K. Gas pressure η is set as 1010 cm−3 except for the ‘low P’ plot where 109 cm−3 was used. Vertical dashed line indicates when populations reach steady-state value as defined in the main text.

Figure 10. Thermalisation of C2− rotational N states during collisions with He, Ar and H2 at 20 K. Initial populations are taken from a Boltzmann distribution at 100 K. Gas pressure η is set as 1010 cm−3 except for the ‘low P’ plot where 109 cm−3 was used. Vertical dashed line indicates when populations reach steady-state value as defined in the main text.

Figure 11. Thermalisation of C2− rotational states during collisions with He, Ar and p-H2(j = 0) (right panel) at 60 K Other parameters are the same as those of Figure .

Figure 11. Thermalisation of C2− rotational states during collisions with He, Ar and p-H2(j = 0) (right panel) at 60 K Other parameters are the same as those of Figure 10.

Table 1. Quadrupole transitions probabilities for ΔN=−2 transitions for C2− and para-H2 [Citation71]. Units of s−1.

Supplemental material

Supplemental Material

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Related Research Data

Beyond the helium buffer: 12C−2 rotational cooling in cold traps with H2 as a partner gas: interaction forces and quantum dynamics
Source: Taylor & Francis
Beyond the helium buffer: 12C−2 rotational cooling in cold traps with H2 as a partner gas: interaction forces and quantum dynamics
Source: Taylor & Francis

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