How visible is ionizing radiation?

Eye adapted to darkness is fairly sensitive to small numbers of photons. See for example the derivation here:

Polaris, bright for a star, is estimated to send 100 000 visible photons per second into a dark adapted pupil.
The rear wheels of Little Dipper are about 15 times dimmer, so about 6000 photons per second.
Since a visible light photon is average of around 2 eV, it can be estimated that a magnitude 5 star sends some 12 or 15 keV per second into eye, and is easily visible.
When we have a radon atom in a dark cellar or bedroom, it undergoes decay and emits an α particle with 5590 keV energy. Then within the next hour it undergoes two β and two more α decays, the second of which (that of Po-214) has 7833 keV energy.
When an α particle is emitted behind closed eyelids, it is stopped within 20 μm or so in cornea. How much of its energy is converted into pure heat, how much into free radicals, and how much into luminescence in visual range? Do we normally see decay events in our eyes, like we do see stars? An α particle should be too slow to produce visual light by Cherenkov radiation inside eyeball, but β particles might.

And a fun video

I particularly liked:

https://pubmed.ncbi.nlm.nih.gov/31669563/

hutchphd said:

I particularly liked:

https://pubmed.ncbi.nlm.nih.gov/31669563/

That was cool.

The first thing that came to my mind was astronauts, I saw a documentary about early space missions a few weeks ago :)

Was this real?
Edit. Just watched a couple of episodes and Dyatolov claims it is Cherenkov radiation as per @malawi_glenn video

Nuclear decays don't have enough energy for Cherenkov radiation in air (which has a refractive index very close to 1). That only works in water. If "the air is glowing" it must be something else.

mfb said:

Nuclear decays don't have enough energy for Cherenkov radiation in air (which has a refractive index very close to 1). That only works in water. If "the air is glowing" it must be something else.

Ok a few questions

I had a look at mechanisms and found this quote.

Within minutes after the steam explosion that caused the Chernobyl accident at 01:23 local time, a number of employees at the power station went outside to get a clearer view of the extent of the damage.

One such survivor, Alexander Yuvchenko, recounts that once he stopped outside and looked up towards the reactor hall he saw a "very beautiful" laser-like beam of light bluish light, caused by the ionization of air, that appeared to be "flooding up into infinity".

From this site.

https://en.wikipedia.org/wiki/Ionized-air_glow#cite_note-Meyer-10

The link outlines how exited molecules can emit photons and form Ozone (metallic taste was mentioned in the drama following the explosion? Although that could be artistic licence? )

Assuming it is excitation photons why would there be a “laser like beam” vertical?

As debris was scattered everywhere would not the light be more diffuse? Or was the beam via the open core where there was most radiation?

Finally if the main radiation from the core was ionizing bottom up to excite O2 and N2, would not those photons radiate spherically rather than a precise vertical beam?

Examining the matter, ZnS clearly is efficient enough in converting ionizing radiation into visible light to see a single α particle by naked eye. This is the basis of spinthariscope and scintillation counting.
Compared to ZnS, how efficient is clear air? How about eyeball itself?

pinball1970 said:

Assuming it is excitation photons why would there be a “laser like beam” vertical?

As debris was scattered everywhere would not the light be more diffuse? Or was the beam via the open core where there was most radiation?

I think to use the light 'beam' of a torchlight in a slightly moist night is a good analogy. The 'beam' is mostly/only visible from close to its origin, since what makes it is just that from that direction you get more scattered light - while the scattered light itself actually goes full spherical.

Also, while you have some stray light close, you won't notice it due the luminosity of the 'beam'.

It's difficult to interpret descriptions like this. Maybe it was air exposed to gamma rays from the core - that could be a beam-like region. Only a small fraction of the gamma emitters left the reactor and that was much more spread out, so the highest radiation doses outside were in the space in direct view of the reactor core.

mfb said:

It's difficult to interpret descriptions like this. Maybe it was air exposed to gamma rays from the core - that could be a beam-like region. Only a small fraction of the gamma emitters left the reactor and that was much more spread out, so the highest radiation doses outside were in the space in direct view of the reactor core.

I found this

https://www.express.co.uk/news/scie...of-light-HBO-Chernobyl-real-nuclear-radiation

"The nuclear expert and a team of researchers examined the blue glow seen at Chernobyl in a 2017 paper published in the journal Nuclear Technology."Which lead to this

https://www.tandfonline.com/doi/full/10.1080/00295450.2017.1384269

The title of this thread has the word 'Visible'. Is it not the case that 'visible' radiation is defined by a particular range of optical frequencies?

All the examples above are of people 'seeing' the results of ionising radiation. X rays are just as likely to hit the retina without passing through and an image being formed by the optics. But you might say that you see them but you wouldn't be able to tell where they come from.

Other examples are when ionising radiation ionises air and we see the visible frequencies produced. Take old flou tubes or even a domestic LEDs - they produce UV (invisible) which is frequency shifted to a visible frequency.

If you say that you are "seeing them" then you may as well say that you 'see' the baseball bat that bangs you on the head and you 'see stars'.

If high energy charged particles were to hit your retina, you could "see" them, you'd probably need several multi-MeV particles at once to create a perceptible flash. Fundamental physics dictates that a high-energy charged particle interacts with matter much as photons do - there's even a technique called the "method of virtual quanta" where you predict this based on an "equivalent photon spectrum" to the EM field of a moving charge. This spectrum extends all the way down to zero frequency, so a high energy charged particle will have some cross-section to excite photopigments that absorb visible light.