Recombination time in air

Question

Conditions Im interested in: air, 1 atm, 300K, very low ionization percentage, electrostatic source of ionization, reduction in ionization percentage two fold. But general answer is ok too.

Data I found for somewhat similar conditions:

Time till collision is about 0.1 nanosecond in oxygen at room temperature and 1 atm, http://www.3rd1000.com/chem101/chem102i.htm

While recombination is 30ns as I see in a graph, but mentioned time is more than a hundred nanoseconds, synthetic air with 20% oxygen and 80% nitrogen, atmospheric pressure and temperature https://iopscience.iop.org/article/10.1088/1361-6463/aae134/pdf

So the main question is: why is recombination time so much longer than collision time? 1000 times

Naively i would think that just a few collisions would be sufficient, and that charged particles will 'seek' each other even better than random collisions due to electrostatic attraction.

Bonus question: am I right that ionization percentage strongly affects recombination time? Strongly ionized gas would re-ionize itself often due to temperature and radiation. Weakly ionized gas would need to spend a long time till rare ionized particles would find each other, not sure which effect wins

P.S. by recombination I mean reunification of an electron and nitrogen or oxygen ion with one electron missing, and emmitting a photon to get rid of energy, or staying in a metastable state with electron at higher energy state. Main condition is non-conductivity, non-interaction with electrostatic field. So that it behaves more like a gas and less like a plasma. And just half of such particles to be united, to avoid the 'last pair will never find each other' complication.

Answer 1

why is recombination time so much longer than collision time?

As seen here, gas kinetic theory predicts that collision frequency $$ Z \propto T^{0.5}$$, however in this research of ion mixture in troposphere, it is noticed that recombination coefficient : $$ \alpha_{_T} \propto T^{-3} $$ So this tells us that certainly NOT a collision rate is responsible for a recombination rate increase. And it's most probably a reverse situation,- as temperature increases - recombination rates drops down. I don't know exact reasons, but I suspect free electron gas temperature also increases, so it becomes more hard for ions to capture them. Besides along recombination, ionization is also going on, which- contrary to recombination,- this time may be assisted by collision rates, because hypothetically atom could be ionized by a good punch to it by a phonon quasi-particle.

Answer 2

Recombination happens during rare three body collisions (because someone needs to consume excess energy from recombination - molecules are not sticky ball and cannot dissipate energy internally).

Ionization however requires only two body collisions.

That is why the balanse is shifted diproportionally in favor of ionization, e.g. normal flame at 1000 deg C or about 0.1eV temperature has quite mesaurable ionization despite the fact ionization requires several eV.