Do tritium sights have a shelf life.  I was reading about tritium and it says it is a radioactive material with a half life of 12.4 years.  This would render the trtium, portion of a sight useless in 12 years.  Anyone have any experience with tritium sights?

Yes, that is correct.

I think I've seen them "guarenteed" for like 11 years,but ya gotta figure by then you will have gone thru four or five sets of whatever sight is the hot new setup,never mind how many pistols...........

Quoted: Do tritium sights have a shelf life.  I was reading about tritium and it says it is a radioactive material with a half life of 12.4 years.  This would render the trtium, portion of a sight useless in 12 years.  Anyone have any experience with tritium sights?

Actually because you are talking 1/2 life of a radio active material, your sights would be only 1/2 their original strength after 12.4 years.  In another 12.4 years (24.8 years from original manufacture) the strength of the sight would lose half of its strength it had at 12.4 years after original manufacture

The half lifes are all great and good but don't accurately reflect the true life of the sites. In 99% of the cases you will lose a bulb well in advance of the half life. It's very common for one to go out for an unknown reason. I have them on several weapons but be prepared to replace them before the 10 or 12 years.

Tritium sights lose half of their luminosity every 12.4 years, but that does NOT mean they lose half of their perceived brightness.

The brightest conditions your eyes can handle are billions of times more intense than the dimmest conditions in which you can see.  But you don't perceive them as billions of times brighter.  A room lit with a 50-watt bulb is perceived as much more than half as bright as the same room lit with a 100-watt bulb.

Luminous EXIT signs that use tritium inserts are supposed to be replaced every 10 years.  But they remain readable and usable for more than 30 years.

I have limited experience doing radio-isotope experiments with such chemicals. The light is given off not by the tritium but by an indicator molecule that interacts with the particles of radio-isotope decay. The energy is released as photons of visible light. My experience with these chemicals was that they are not terribly stable chemically. Clearly in the 20 years since I worked with them they have made some improvements if they now last for years but I will bet that this is the reason for short life noted above.

Not photons but electrons that why it is decaying, its losing electrons, the light perceived is the electron being blasted awayin which the *******, is released, Tapered-pin you have it on the money, seb 127, the vials crack and crap like that, but that has nothing to do with half life, the boy is learning.
GG
No photons period. Alpha particles and stuff like that, heavy patricles, reacting, with something like dharhead said, but I dont know what, yet.
GG2

Originally Posted By Gun Guru: Not photons but electrons that why it is decaying, its losing electrons, the light perceived is the electron being blasted awayin which the photon is released, Tapered-pin you have it on the money, seb 127, the vials crack and crap like that, but that has nothing to do with half life, the boy is learning. GG

Wrong

It's been awhile since I took chemistry, but the tritium isotope can't be losing electrons or else it becomes a different element altogether with a different atomic number. Half-life refers to the time it takes for half the nuclei in a radioactive isotope to decay by the emission of beta particles. For tritium it's a little under 12.5 years. I don't know that that's true about "perceived brightness" because my Trijicons don't seem as bright as they were five years ago, though still useable.

This is my expierence with tritium sights.
In 1986 I bought a IMI Galil with the tritium sights.
Today Dec 2001 they don't glow anymore.
Well they actually stopped several years ago but I can't remember when. The 12.4 years figure is pretty close I always thought it was 10.
So yes they do have a shelf life.

Does anyone know a company who can replace the radioactive part? I like to have them glow again.

From www.ptnightsights.com

"Gunsights which are identifiable by radioluminescent capsules installed into front and rear sights. Decay of Tritium H3 creates soft beta rays that, when they strike the phosphor particles that coat the inside of the glass microsphere, are converted to visible light. Tritium's half life (the time required to reduce the illumination level by 50%) should be about 12.5 years. With a functional life exceeding 15 years."

When I got a set of PT Night Sights 4 months ago, I was told that the 15 year warranty had been changed to 'life time', for the original purchaser.

I'll let you know in 15 years, maybe less..
SSD

radio-isotope half life and useful sight life are separate issues. Half life of a nuclide simply means that in 12.3 yrs there will be half the tritium remaining as were begun with and hence half the decay rate and subsequent luminescence of the sight. In 12.3 yrs will be half as bright, in 24.6 yrs 25%, etc, all other things being equal(which, obviously, they are not).
The tritium(one proton and two neutrons in the nucleus)does decay by losing an electron from its nucleus.
A common misconception is that radioactive materials glow, or release visible light. They DO NOT. Hence the need for another molecule that will interact with these released particles and thus give off visible light.

Early failure of tritium sights are caused by small cracks that form in the glass tubes. They are caused by improper installation and or jarring from droping, bumping and recoil.

Quoted: It's been awhile since I took chemistry, but the tritium isotope can't be losing electrons or else it becomes a different element altogether with a different atomic number.

But that's exactly what occurs. Tritium( H3 ) has 1 proton and 2 neutrons. The stable form of hydrogen has 1 proton only in the nucleus. Deuterium has 1 proton and 1 neutron and is also unstable. Tritium decays "up" to He3 which is a helium isotope. H3 releases a neg electon which causes a neutron to become a proton. Hence, it is now helium-2protons but only 1 neutron. Radio-isotopes can decay with release of various particles but each will decay in a predictable fashion. Some release alpha, beta and gamma. Some only beta, etc. Each radioisotope will decay to another, and another, etc until a stable isotope is reached. Once again, this whole process is predictable, although some isotopes will have more than one way in which they can decay and may have more than one pathway in which to go to acheive stability. Each pattern can have its own half life.

Heavy atoms exist thanks to gravity as small particles coalesced together to form stars, and as gravitational forces increased with more matter accumulating fusion occurs leading to the creation of larger atoms. In essence we are created of star dust as the song goes. When some of these stars went supernova the resulting implosion and subsequent explosion sent matter flying through space. New stars, planets, etc form and the cycle goes on and on. In the early universe there was really no matter, only energy. The two are convertible and only after light particles(hydrogen) accumulated did heavier atoms become possible through fusion. For instance, a positron(positive electron, which is anti-matter) and electron can and will collide to form a photon. the reverse is also possible. Some matter particles even release anti-matter particles as part of their decay process. Okay, I know, I'm beating it to death and I'll shut up now.

Thanks drjarhead. Beta particles can be either positive or negative. Positive beta particles are called positrons and negative beta particles are called negatrons, and though they have the same mass as electrons, technically they're not the same as electrons. From what I remember from basic chemistry class, the nucleus in atoms contains protons and neutrons (nucleons) while electrons revolve around the nucleus like planets revolve around the sun. The beta decay with tritium also involves antineutrinos, which are ejected from the nucleus along with the negatrons to where the atom loses one neutron and gains one proton until the unstable hydrogen-3 isotope (tritium) becomes stable helium 3 atoms. This is probably more information than anyone needed to know so I'll quit now.

Okay drjarhead, you had me until the "Big Bang" theory.  I thought heavier isotopes were possible because of higher NP ratios/increase in binding energy?, and most of the heavy elements and their isotopes decay by alpha decay, neutron decay or SF.  While the beta particle interacts with a phosphor to produce the green glow of weapons sights, in high concentrations, even the low energy beta (.0186 Mev) emission of H3 will glow all by it's lonesome, i.e. Cerenkov.

Problems with Tritium sights include decay of the radioactive element and leaking/leaching of the H3 from the sight vial.  You will never know about the latter (unless you have access to a LSC), and the former problem can't be helped (unless you've found a way to circumvent nuclear physics, in which case I happen to have a big pile of lead available waiting to be turned into gold).  Tritium (H3) has a half-life of 12.3 years.  While it will not be considered stable (used up/all gone) for seven 1/2T, it just makes since that the less you have of a substance that gives off light/interacts to cause emission of a light photon, the dimmer and less usable that light will be.  Think of your tritium sights as being battery powered... with batteries that last for 10+ years.  

Quoted: Okay drjarhead, you had me until the "Big Bang" theory.  I thought heavier isotopes were possible because of higher NP ratios/increase in binding energy?, and most of the heavy elements and their isotopes decay by alpha decay, neutron decay or SF.  While the beta particle interacts with a phosphor to produce the green glow of weapons sights, in high concentrations, even the low energy beta (.0186 Mev) emission of H3 will glow all by it's lonesome, i.e. Cerenkov. Problems with Tritium sights include decay of the radioactive element and leaking/leaching of the H3 from the sight vial.  You will never know about the latter (unless you have access to a LSC), and the former problem can't be helped (unless you've found a way to circumvent nuclear physics, in which case I happen to have a big pile of lead available waiting to be turned into gold).  Tritium (H3) has a half-life of 12.3 years.  While it will not be considered stable (used up/all gone) for seven 1/2T, it just makes since that the less you have of a substance that gives off light/interacts to cause emission of a light photon, the dimmer and less usable that light will be.  Think of your tritium sights as being battery powered... with batteries that last for 10+ years.

Heavier atoms(heavier than hydrogen) were virtually all made in stars. Only there are the gravitational forces great enough to force nuclei together( a little oversimplified). This takes tremendous energies to accomplish which is why "cold fusion" cannot work.
Your final paragraph is correct, obviously.
Heavier radioiostopes often do release alpha particles as well as other subatomic particles. Each is diferent in the way in which it decays. You need a nuclide chart to actually appreciate this. If interested they are available at any university bookstore.
I really don't believe that radioactive materials glow, per se. In very high concentrations the products of decay may interact with other atoms to result in the release of visible light. Beta particles do not give off light but can interact with others. I've addressed that previously in another thread. When nuclei decay to give off photons they are gamma rays and are at the extreme range of the electromagnetic spectrum. ie essentially identical to Xrays. Difference is one is released from nucleus, one from changes in electron energies outside the nucleus. In any event, the frequency is very high, the wavelength is very short and the enery is very high for a photon. Hence, more damaging. Freq and wavelength are inversely proportional by law. Energy increases for electromagnetic waves/photons as freq increases which means a decrease in wavelength. In any event, nuclei do not release visible light, at all, that I know of. If you know something I don't I would of course be interested in a source. Always looking to expand my knowledge.

I take it you don't buy into the Big Bang Theory?? Even according to Genesis prior to the creation of the universe all was "null and void" and then there was "light". FWIW, IMHO, The story of creation in Genesis very closely parallels the evidence for creation and evolution of this planet, etc. It amazes me that both sides of the debate have such difficulty realizing this. It also amazes me that humans had knowledge of this. Absolutely incredible.

MERRY CHRISTMAS!!!!!!!!

Actually drjarhead, the heavier elements(Actinide Series) are all manmade radioisotopes.  The GE Nuclear Energy Nuclides and Isotopes - Chart of the nuclides, is indeed a good source of information.  I have the 14th edition as part of my desk reference.  My University days are long behind me.  Cerenkov radiation is associated with extremely high beta fields.  It occurs when the beta particles interract with surrounding media and excite those molecules to the point that energy is released in the form of visible light.  The light photons are produced without interraction with a conversion media (i.e. photocathode, interactive phosphor)  I have seen this using a cobalt-60 source in water and have seen pictures of this using T3 in air.  It is the same "glow" given off by newly irradiated fuel rods.

My reference to heavier elements is in regards to all atoms heavier than hydrogen. The manmade Actinide series you refer to are so unstable that they exist only briefly prior to decay. No doubt these are also made in stars but we would never be aware as their half-life is so brief. Nor would they therefore be found anywhere else in nature.
I do not dispute the existence of Cerenkov radiation. My point was that it is an indirect result of radioactive decay and not a direct one. Alpha, Beta, gamma and neutrons are not visible as I am sure you're aware. Only when there is an extremely high density of beta particles are enough photons of visible light given off by nearby atoms to be noticeable. To be nearby such a source would be a very bad idea.

And they say us gun nuts are just yokel rednecks in the boonies :)

Green_Furniture, is the Luminox you are talking about somehting that has to be "charged" by light exposure? I know must of my guns sit in safes or drawers, not readily exposed to a charging source. I would hate to draw my pistol at night and realize I had forgotten to leave it in the sun that day. If it is something that always glows, like tritium, then we will get it once some military adopts its use and "proves" it to the rest of us. LAter.

jason, I'd never heard of Luminova so I looked it up. It has to be charged by a light source but supposedly the charge lasts longer.

OTOH, tritium does NOT have to be charged and puts out a useable glow for about 15 years.

On the upside Luminova doesn't have to be replaced, unlike tritium, in which the vials have to be replaced in night sights. I have a Luminox watch that uses tritium and it's very bright in total darkness. I don't know what I'll do when it runs out in 15 years. I suppose I'll have to buy a new watch.

Thanks Big_Bear. Thats what I figured. A watch gets considerable "outside" time to charge the glow elements, while firearms don't. I remember "Bright Sights Ghost Glow" luminescent paint, which I thought was hot sh*t until I put it on and realized that my pistol spends its time securing the night stand drawer, not patrolling the beach getting sun exposure. So I slurged and got tritium night sights that work all the time, not just when I have advance warning of a break-in and can prepare. LAter.

Phosphorescence/luminescence and fluorescence work based on the same principles. They occur outside the nucleus and perhaps this is what Big Bear initially alluded to. They are a result of electrons "circling" the nucleus changing energy levels. Only specific quanta of energy(photons) can be absorbed by given electrons. Energy of a photon dictates frequency and therefore wavelength. Further only specific quanta of energy can be released by said "excited" electron. May release various quanta but these are set and specific. This is why different things have different colors.
Substances which release their energy slowly are luminescent. Those which do so rapidly are fluorescent. Turn off a fluorescent light and see what happens.
Electrons are gained and lost by atoms in chemical reactions. This is the basis of chemistry. However, these are outside of the nucleus. One can argue that the electrons are shared between atoms as well as, in fact, they are. This is also why inert gases are used for fluorescent lights. Otherwise what would result is probably a small explosion and fire.

Gee you guys are smart. Like I said, it's been awhile since I studied this stuff. They used to teach that in conductors, electric current flows from negative to positive as electrons jump from atom to atom, leaving positively charged holes behind for the next electron to fill. Then there was the "hole flow" theory, where current flows from positive to negative due to positively charged holes flowing backwards towards negatively charged electrons. I don't know if they still teach the "hole flow" theory or not.