nagyepf
Harmless
Posts: 49
Registered: 1-9-2017
Member Is Offline
Mood: No Mood
|
|
Radium,actinium,polonium and radon glow
I think all of us know the story that when Pierre and Marie Curie isolated enough radium and polonium salts they found it to glow blue-green in the
dark.The same properties were soon discovered with actinium and radon by other scientists like André-Louis Debierne,Rutherford, Robert B. Owens,
Friedrich Ernst Dorn, Harriet Brooks,William Ramsay,Robert Whytlaw-Gray, Friedrich Oskar Giesel,Harriet Brooks,Otto Hahn and Otto Sackur,and probably
lots of others.
-----------------------------------------------------------------------------------
Here's something that is still not completely explained today:A popular explanation for the glow is that alpha particles ionize nitrogen in the
air,hence the glow.
Does this mean that if we put radium,actinium or polonium in vacuum we wouldn't observe glow at all?
[Edited on 02-09-2017 by nagyepf]
[Edited on 02-09-2017 by nagyepf]
|
|
|
annaandherdad
Hazard to Others
Posts: 387
Registered: 17-9-2011
Member Is Offline
Mood: No Mood
|
|
There are mechanisms by which a radioactive substance can produce light without surrounding gas. The particles (alpha, beta and gamma) are generally
emitted inside the radioactive material (e.g. radium chloride) and are capable of ionizing atoms on the way out. These will then fall back to their
ground states, emitting photons, some of which may be optical. Also, when a charged particle is emitted from a nucleus (alpha, beta) the charge of
the nucleus changes, and the electron cloud in the atom has to adjust itself to the new nuclear charge. In more detail, this means that the ground
state of the atom with the old nucleus is not the ground state of the atom with the new nucleus; it is a linear combination of the new ground state
plus various excited states; the latter then decay toward the ground state, emitting photons. Also, if the nucleus emits an alpha particle, then the
atom left behind has too many electrons, for example, neutral Ra emits an alpha and produces Rn--. Surely Rn, a noble gas, does not have a stable
ion Rn--; rather, the two extra electrons are freed, with some energy to spare. These are capable of producing a photon by several mechanisms.
Finally, when a charged particle is emitted, there is a certain probability for a photon to be emitted at the same time; this may well be a higher
energy photon, but it could be optical.
None of this is to say that the light emitted is in the visible range (some of it is, some not), or that the intensity is enough to be comparable to
the light produce by ionization of surrounding gas.
Any other SF Bay chemists?
|
|
|
nagyepf
Harmless
Posts: 49
Registered: 1-9-2017
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by annaandherdad  | There are mechanisms by which a radioactive substance can produce light without surrounding gas. The particles (alpha, beta and gamma) are generally
emitted inside the radioactive material (e.g. radium chloride) and are capable of ionizing atoms on the way out. These will then fall back to their
ground states, emitting photons, some of which may be optical. Also, when a charged particle is emitted from a nucleus (alpha, beta) the charge of
the nucleus changes, and the electron cloud in the atom has to adjust itself to the new nuclear charge. In more detail, this means that the ground
state of the atom with the old nucleus is not the ground state of the atom with the new nucleus; it is a linear combination of the new ground state
plus various excited states; the latter then decay toward the ground state, emitting photons. Also, if the nucleus emits an alpha particle, then the
atom left behind has too many electrons, for example, neutral Ra emits an alpha and produces Rn--. Surely Rn, a noble gas, does not have a stable
ion Rn--; rather, the two extra electrons are freed, with some energy to spare. These are capable of producing a photon by several mechanisms.
Finally, when a charged particle is emitted, there is a certain probability for a photon to be emitted at the same time; this may well be a higher
energy photon, but it could be optical.
None of this is to say that the light emitted is in the visible range (some of it is, some not), or that the intensity is enough to be comparable to
the light produce by ionization of surrounding gas. |
Thats a good explanation,thanks.I never really understood why everbody forgets to mention 2 electrons when talking about alpha decay.
Oh and another thing i'm thinking about is could we create alpha perticles form helium gas by making it into a plasma state?Thus having 2 free
electrons and a helium nuclei?
|
|
|
annaandherdad
Hazard to Others
Posts: 387
Registered: 17-9-2011
Member Is Offline
Mood: No Mood
|
|
Yes, if you take any substance and heat it enough you will get a fully ionized plasma in which the atoms are stripped down to bare nuclei. But the
energy required to strip electrons off goes like Z^2 where Z is the nuclear charge, so for higher Z it can take extremely high temperatures to fully
ionize the atoms. Helium has only Z=2, but still removing the second electron requires an energy of 54 eV. But, for example, inside the sun the
helium is fully ionized, and you have a soup of protons, electrons and alpha particles (mostly, there is a small admixture of heavier elements). In
the surface layers of the sun the protons make about 75% of the mass and the alpha particles 25%, roughly. Those are the abundances of hydrogen and
helium created in the big bang, which is still maintained in the surface layers of the sun. In the core of the sun the percentage of helium has gone
up, due to fusion.
Any other SF Bay chemists?
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
