Where do positrons come from?

This is a question that everyone present began to think about after the excitement.

"Chen, where did you say this positively charged positron came from? Could it be that something is wrong with the cloud chamber, which is not actually a particle track, but a dust track inside? ”

Kapitsa even threw the problem back into Chen Muwu's hands.

The latter nodded thoughtfully: "Quite possibly, let me look on other photographic negatives to see if there are any other tracks." ”

Rutherford felt in his heart that Kapitsa was just messing around, why did Chen Muwu also mess around with him?

He had just calculated that the charge-to-mass ratio of this particle and the charge-to-mass ratio of electrons are the same thing, but the size of the deflection in the magnetic field is different.

It was clear that it was a positively charged electron, so why did he echo Kapitsa that it was a speck of dust that had strayed into the chamber of mist?

However, it is better for Chen Muwu to look for it again, if there is only one photographic negative with positrons, then it is likely to be an accidental phenomenon, maybe at a certain moment, a beam of cosmic rays just shot into the cloud chamber.

However, if positron trajectories are also found on other photographic negatives, it is very likely that the experiment of bombarding boron crystals with alpha particles did produce a second product, positrons, in addition to neutrons.

In fact, Chen Muwu didn't know the bottom in his heart, whether he could find a positron trajectory in the photographic negative.

Boron is present in nature with two stable natural isotopes, boron-10 and boron-11.

The abundance of the former is about 20 percent, while the abundance of the latter is about 80 percent.

Only after the alpha particle reacts with boron-10 to produce nitrogen-13, can it rapidly release a positron and then decay into stable carbon-13.

However, if the alpha particle and boron-11 have a nuclear reaction, then the reaction product is the more stable carbon-14, and there is also a neutron, and carbon-14 is less prone to further decay.

The proportion of boron-10 and boron-11 varied from one boron sample to another, but in general the latter was more predominant.

When Chen Muwu was in the Cavendish laboratory, he was lucky enough to discover a positron from a boron crystal.

This time at the Prince's College in Stockholm, he was lucky for a second time.

Originally, the proportion of boron-10 is small, and when nitrogen-13 releases positrons, it is possible in all directions.

Could the released positrons just happen to enter the cloud chamber?

Can new tracks be found in other photographic negatives?

Chen Muwu had fifteen buckets of water in his heart, seven up and eight down.

He can't give a definite message unless he can actually find a second track.

Fortunately, because neutrons were used to bombard the nuclei of hydrogen, deuterium, and helium, a large number of photonegatives were taken, much more than the one Chen Muwu had in the Cavendish laboratory.

From these photographic negatives, it is not difficult to find a photograph of the positron trajectory.

It can't be said that it is not difficult, perhaps it should be said that Chen Muwu is lucky.

The reappearing positron trajectory is calculated to have the same charge-to-mass ratio as the electron, but in the opposite direction of deflection in the magnetic field.

If the trajectory appears only once, it can be said to be dust, but the trajectory of positrons appears on two photographic negatives with different space-time environments, so it is a sure thing that positrons will appear in the reaction products.

Then there is another question, where do positrons come from?

Because Chen Muwu has discovered neutrons, answering this question has become a lot simpler all of a sudden.

"That's how I think about positrons."

Chen Muwu continued to write on the scratch paper on which he calculated the positron trajectory, and the people around him leaned their heads one after another.

"Now that neutrons have been discovered, and the mass of the neutron is basically the same as that of the proton, we can make such an assumption.

"The alpha particle has a positive charge of 2 and its relative atomic mass is about 4, so it can be assumed that the alpha particle is a helium nucleus composed of two protons and two neutrons combined.

"Correspondingly, the boron crystals on the target, I don't know if it should be boron-10 or boron-11, their nuclei should be a combination of five protons and five or six neutrons.

"I think we only need to test what type of products can be obtained on the target after being bombarded by alpha particles, and we can probably know where the neutrons and positrons in the counterreaction come from.

"Professor Bierman, you are the President of the International Union of Pure and Applied Chemistry, and you are better at examining chemical products than any of us here.

"I'm going to have to work hard for you this time."

Chen Muwu almost said it again this time, saying all the things like nitrogen-13 and carbon-14.

Chen knows that carbon-13 occurs naturally in nature, and that Professor Aston at the Cavendish Laboratory has measured this isotope when he measures the mass of various isotopes.

Carbon-14 has not yet been discovered by the chemical community, and Chen Muwu also knows this.

But he didn't know if the chemical community knew about nitrogen-13 now, anyway, there happened to be a chemistry professor Bierman who was also in Stockholm, so he asked him to go down and test what the boron crystals had become after being bombarded.

Chen Muwu took down the bombarded boron crystal target from the experimental device that had been closed long ago and handed it to Bierman.

Bierman went to make an identification, and the results of Zhao Zhongyao and Cockcroft's bombardment of the deuterium nucleus with gamma rays were not yet available.

The few people who stayed behind suddenly didn't know what to do next.

"Chen, in fact, do you already know where this positron comes from?"

Rutherford suddenly approached Chen Muwu's side and asked.

Chen Muwu nodded subconsciously and shook his head: "I just have a general idea.

"It turns out that in your imagination, sir, the neutron is a combination of a proton and an electron.

"So when a proton captures an electron, it becomes a neutron.

But at the time you came up with this theory, people never thought that there was such a thing as a positively charged electron in the universe.

"Now that the trajectory of the positron has been clearly recorded on the photographic negatives in the cloud chamber, is it possible that the proton actually released a positively charged electron outward, which then became a neutron?

"And the positively charged electrons can easily meet a large number of negatively charged electrons in the surrounding environment, and perhaps they will be annihilated, so people have the illusion that a proton captures a negative electron and produces a neutron."

Chen Muwu gave an answer that was completely contrary to the facts, but it sounded very reasonable.

You can't talk about this thing in detail, and you may unconsciously talk about neutrinos when you talk about it.

And among these people in Stockholm is Bohr from Copenhagen.

Before and after the discovery of neutrinos, he once again made his view that energy is not conserved at the onlooker level.

Chen Muwu was afraid that the topic would come to the aspect of energy conservation, so he made a mistake in using it.

Let's first understand the properties of positrons and positrons and the decay of positive and negative betas, and then let's talk about neutrinos.

Otherwise, the steps are too big, and it is easy to pull the eggs.

Chen Muwu's original intention was to fool Rutherford by saying an answer that sounded reasonable at first glance, but was actually wrong.

But he didn't expect that he had done something wrong again.

Because a few days later, Zhao Zhongyao and Cockcroft also did the experiment of bombarding the deuterium nucleus with gamma rays.

Their experiments showed that the binding energy of the deuterium nucleus was 2.2 megaelectron volts, and the mass of the neutron should be 1.0084 relative to atomic mass units or 1.0090 relative to atomic mass units.

Either number, it is larger than the known sum of proton mass plus electron mass of 1.0078 relative atomic mass units.

This result not only shows that the neutron is not a "system of attachment and binding of protons and electrons", as Rutherford envisaged in his hypothesis, but should be a basic and "indivisible" new particle.

It seems that the result is all happy, but there is another problem.

Neutrons are not a binding system composed of protons and electrons, so are protons a binding system composed of neutrons and positively charged positrons?

In this instant, Rutherford thought of a new possibility.

He just wanted to open his mouth to express his opinion to Chen Muwu, but after thinking about it again, he couldn't help but shake his head.

Protons and electrons are able to form a binding system because they are two of them, one positively charged and the other negatively charged.

However, the neutrons themselves are not charged, while the positrons are positively charged, and there is no electrical opposite characteristic between the two, so what force can they rely on to bind each other?

Rutherford felt that Chen Muwu's statement just now seemed to be very unreliable.

Because since I discovered the proton in 1919, it has been ten years now.

In the past ten years, people have seen a large number of protons and electrons in the trajectory of the cloud chamber and in various experimental phenomena.

But only Chen Muwu found the neutron, not to mention the positron that he had basically never seen.

It can be seen that even if, as Chen Muwu said, the proton radiates a positron outward, and then decays into a neutron, then this reaction is definitely not common and can not occur easily.

Of course, there is another possibility, that is, what Chen Muwu said is wrong, the positron does not come from protons, but has another source.

Of course, in any case, the discovery of neutrons and positrons in one fell swoop is a very big event for physics.

It can even be said that only half of 1928 has passed, and the two particles discovered by Chen Muwu in Stockholm have been declared the most important and high-profile scientific discoveries of this year.

Compared with these two particles, Chen Muwu's previous invention of the cyclotron and the two new chemical elements created on the cyclotron are also important scientific discoveries, but they are ......

Rutherford suddenly remembered that he had compared Chen Muwu's first arrival at Cambridge University to Einstein in 1905.

Because in that year, Chen Muwu made countless achievements in physics and astronomy.

Rutherford felt that by 1928, Chen Muwu seemed to have regained his second spring and achieved so many results.

And in Rutherford's eyes, these results were even more powerful than the previous one.

Maybe 1923 was not Chen Muwu's miracle year, 1928 was, right?

Soon after, Bierman also gave his own test results.

He detected two isotopes of carbon from the bombarded boron crystal target:

"Dr. Chen, inside this target, there is a nuclear reaction product that is carbon-13, which is an isotope of carbon that chemists have found in nature.

Another reaction product is a new isotope of carbon, carbon-14 with an atomic mass of 14.

"I consulted the relevant materials and papers, and this is a new isotope of the element carbon that has never been discovered before!"

Bierman was thrilled.

But he saw the reaction of the crowd again, especially the expression on the face of Rutherford, the leader of the Cavendish Laboratory.

Obviously, they don't seem to be paying much attention to the new carbon isotope they have detected.

Bierman thought about what Chen Muwu had done at Prince's College in Stockholm these days.

Bierman doesn't know much about the results of physics, but he still has a lot of say in chemistry.

Just the new elements, Chen Muwu has already discovered two kinds of them on the cyclotron.

Compared to a new element, a new isotope is really not worth mentioning.

Chen Muwu has never made a statement on Bilman's test.

He didn't find nitrogen-13 that decayed quickly, and thought that carbon-14 was not important, although there were many slots, but Chen Muwu did not point it out.

This time, he agreed with Bierman's view that the carbon-14 produced in the laboratory is not a good carbon-14, and only the carbon-14 found in nature is a good carbon-14.

Next, I will compile and publish the results of physics and chemistry that I have recently achieved at Prince College.

Everyone knew that Chen Muwu wanted to run the "Journal of Prince College", so no one mentioned the matter of publishing his papers in other journals and magazines.

Only Rutherford, in his name, went to the telegraph office and sent a telegram to the editorial office of the journal Nature in London, asking them to place an advertisement prominently in the latest issue.

"The neutron has finally been discovered, as detailed in the inaugural issue of the Journal of Prince College, which will be published in the near future."

(End of chapter)