Editing Hydronium (section)

===Interstellar chemistry===
As mentioned previously, {{H3O+}} is found in both diffuse and dense molecular clouds. By applying the [[reaction rate]] constants (''α'', ''β'', and ''γ'') corresponding to all of the currently available characterized reactions involving {{H3O+}}, it is possible to calculate ''k''(''T'') for each of these reactions. By multiplying these ''k''(''T'') by the relative abundances of the products, the relative rates (in cm<sup>3</sup>/s) for each reaction at a given temperature can be determined. These relative rates can be made in absolute rates by multiplying them by the {{chem2|[H2]^{2}|}}.<ref name=udfa>{{cite web|title = H<sub>3</sub>O<sup>+</sup> formation reactions|url = http://udfa.ajmarkwick.net/index.php?species=41|work = The UMIST Database for Astrochemistry}}</ref> By assuming {{math|1=''T''&nbsp;=&nbsp;10&nbsp;K}} for a dense cloud and {{math|1=''T''&nbsp;=&nbsp;50&nbsp;K}} for a diffuse cloud, the results indicate that most dominant formation and destruction mechanisms were the same for both cases. It should be mentioned that the relative abundances used in these calculations correspond to TMC-1, a dense molecular cloud, and that the calculated relative rates are therefore expected to be more accurate at {{math|1=''T''&nbsp;=&nbsp;10&nbsp;K}}. The three fastest formation and destruction mechanisms are listed in the table below, along with their relative rates. Note that the rates of these six reactions are such that they make up approximately 99% of hydronium ion's chemical interactions under these conditions.<ref name=rauer1997ica /> All three destruction mechanisms in the table below are classified as [[dissociative recombination]] reactions.<ref>{{Cite web|title=Dissociative recombination {{!}} physics|url=https://www.britannica.com/science/dissociative-recombination|access-date=2021-09-30|website=Encyclopedia Britannica|language=en}}</ref>
[[Image:PrimaryH3OPathways.png|thumb|Primary reaction pathways of {{H3O+}} in the interstellar medium (specifically, dense clouds).]]

{|border="1" cellpadding="5" cellspacing="0" align="center" class="wikitable"
|-
! rowspan="2" | Reaction
! rowspan="2" |Type
! colspan="2" | Relative rate (cm<sup>3</sup>/s)
|-
! at 10 K
! at 50 K
|-
|{{chem2|H2 + H2O+ -> H3O+ + H}}
|Formation
|2.97{{e|-22}}
|2.97{{e|-22}}
|-
|{{chem2|H2O + HCO+ -> CO + H3O+}}
|Formation
|4.52{{e|-23}}
|4.52{{e|-23}}
|-
|{{chem2|H3+ + H2O -> H3O+ + H2}}
|Formation
|3.75{{e|-23}}
|3.75{{e|-23}}
|-
|{{chem2|H3O+ + e(-) -> OH + H + H}}
|Destruction
|2.27{{e|-22}}
|1.02{{e|-22}}
|-
|{{chem2|H3O+ + e(-) -> H2O + H}}
|Destruction
|9.52{{e|-23}}
|4.26{{e|-23}}
|-
|{{chem2|H3O+ + e(-) -> OH + H2}}
|Destruction
|5.31{{e|-23}}
|2.37{{e|-23}}
|}
It is also worth noting that the relative rates for the formation reactions in the table above are the same for a given reaction at both temperatures. This is due to the reaction rate constants for these reactions having ''β'' and ''γ'' constants of 0, resulting in {{math|1=''k''&nbsp;=&nbsp;''α''}} which is independent of temperature.

Since all three of these reactions produce either {{H2O-nl}} or OH, these results reinforce the strong connection between their relative abundances and that of {{H3O+}}. The rates of these six reactions are such that they make up approximately 99% of hydronium ion's chemical interactions under these conditions.