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Communication Dans Un Congrès Année : 2022

Is it worth to investigate such phenomena, which are predictable with a good accuracy?

S. Demes
François Lique

Résumé

Astronomy and astrophysics is a field of science, which evolves rapidly due to the technological progress. The recent telescopes allow one to carry out observations very efficiently, giving a possibility to look into various regions of the Universe. In order to correctly interpret the observations, however, complementary research is required: laboratory measurements and/or theoretical modellings. For instance, when a molecular species is observed in Space, there is a need for precise collisional and spectroscopic data in order to correctly describe the physical conditions of the astronomical environment, from where it was detected. Very often the spectroscopic and especially the collisional data are challenging to get, both from experimental and also from theoretical perspective. The calculation of collisional rate coefficients could be calculated only from sophisticated quantum-theories. Such calculations are very computationally demanding, so one should carefully choose the boundaries of calculations (e.g. making limitations on energy, temperature, etc.) and also properly select the possible approximations, which can be applicable. To estimate the rate coefficients for molecular collisions involving H2 (which is the most abundant molecule in interstellar clouds), often the collisional data with helium atom. Many studies have shown earlier that a multiplicative factor of 1.4 applied on rate coefficients calculated for He could be a good approximation for collisional rates for molecular hydrogen. This is based on their similar electronic structure and small effective size. Several studies shown however the strong limitations behind this crude approximation, concluding that collisional data for H2 is highly necessary for precise astrophysical applications. On the other hand, while analysing the rate coefficients for collisions of ionic species with para- or ortho- H2 nuclear spin-selected molecules, we find that the collisional rates are very similar, the difference between them is usually less than 10–20 %, which is far within the required “astronomical precision”. Since the calculation of rate coefficient for collisions both with para- and ortho-H2 are very demanding, the following question arises: is it really worth to investigate such phenomena, which are predictable with a good accuracy? Is it valid from a critical scientific perspective to calculate/measure a value (e.g. a collisional rate coefficient for para-H2) and then “suppose” the same value for another quantity (e.g. the corresponding rate coefficient for ortho-H2) based on previous general experiences?
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Dates et versions

hal-03721006 , version 1 (12-07-2022)

Identifiants

  • HAL Id : hal-03721006 , version 1

Citer

S. Demes, François Lique. Is it worth to investigate such phenomena, which are predictable with a good accuracy?. TUMLA Philosophy of Astrochemistry Workshop, Jul 2022, Rennes, France. ⟨hal-03721006⟩
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