The idea of bombarding deuterium nuclei with protons, that is, hydrogen nuclei, was entirely based on Rutherford's wishful thinking after learning that Chen Muwu had separated hydrogen isotopes from liquid hydrogen.
Let’s not talk about the difficulty of preparing deuterium gas. Anyway, since Chen Muwu discovered deuterium, British Air Company has taken over the deuterium gas production work of various universities that use a small amount of it. Although they use the same distillation method as Chen Muwu, the purity is not the same. high.
Using deuterium as a target is purely laborious and thankless. First of all, deuterium is a gas under normal temperature and pressure and is difficult to control.
Secondly, there is one proton and one neutron in the deuterium nucleus, and the number of neutrons accounts for 50%.
There are two protons and two neutrons in the helium nucleus, and the proportion of neutrons is still 50%.
Of course, helium has the same problem as deuterium, that is, it is also a gas.
But when it comes to the lithium atom, it has three protons and four neutrons, and the number of neutrons accounts for more than half.
If protons can really be used to bombard neutrons out of atomic nuclei, then atoms with a higher probability of bombarding neutrons should be used as targets.
What's more, Chen Muwu also knows that no matter if protons are used to bombard deuterium, helium or lithium nuclei, the neutrons in the nuclei will never be ejected.
But bombarding lithium nuclei with protons is indeed a feasible experiment.
When it comes to crossing the river by touching other people's stones, Chen Muwu has the most say.
The person he wanted to touch this time was none other than Cockcroft, who was currently beside him and assisting him in designing and manufacturing the proton source.
In the original history, after Cockcroft successfully developed the particle accelerator in the Cavendish Laboratory, the first experiment he conducted was to use high-energy protons accelerated by the accelerator to bombard a target made of lithium metal. .
There are two advantages to using lithium metal as a target:
The first is that it is a solid. Although its chemical properties are very active, it is much easier to control than invisible and intangible hydrogen (deuterium) and helium.
Second, it is because the atomic number of the lithium atom is small, the radius is also small, and there are not many nucleons in the nucleus, which is commonly known as a light nucleus.
In this way, the accelerated high-energy protons can easily enter the interior of the atomic nucleus and undergo a nuclear transmutation reaction with the nucleus.
For protons and lithium nuclei, the specific nuclear reaction between the two is that the proton enters the interior of the lithium nucleus and changes the nuclear charge of the nucleus from three to four.
Lithium-7, which has three protons and four neutrons, has also become beryllium-8, which has four protons and four neutrons.
On the periodic table of elements, the relative atomic mass of beryllium is 9. This means that most of the stable beryllium elements that appear on the earth appear in the form of beryllium-9 with four protons and five neutrons.
For beryllium, beryllium-8 is just an unstable isotope. After being produced by bombardment, it will soon split due to instability and evenly split into two identical helium nuclei.
In other words, the lithium element at the target position will emit two alpha particles after being bombarded by high-energy protons.
This nuclear reaction is not only the first time to use artificially accelerated particles to carry out nuclear transmutation of atomic nuclei, but also the first time to experimentally prove the correctness of Einstein's mass-energy equation.
Whether it is the mass of the proton and lithium atom before the reaction, or the mass of the two alpha particles after the reaction, measuring the mass of these particles is no problem at all for the development of modern science. It is easy to obtain specific results in the laboratory. numerical.
Just by doing two simple addition calculations and an equally simple subtraction calculation, it can be easily concluded that the mass sum of the particles before and after the reaction is inconsistent, which is a so-called mass loss.
According to Einstein's mass-energy equation, E=mc, it is easy to calculate how much energy is converted into by this part of the mass loss.
And of course this part of energy will not disappear out of thin air.
As long as we measure the binding energy released during the entire reaction of the nuclear reaction just now, and compare the experimental data with the theoretical calculations, we can know whether Einstein's theory is right or wrong.
In the original historical process, Einstein proposed this formula as early as 1905, the miracle year.
But it was not until twenty-seven years later that it was finally confirmed by Cockcroft in his particle accelerator.
The time span during this period is really too big.
But it also shows how visionary the great and genius Einstein was!
Although Chen Muwu moved the experimental verification date forward by five or six years this time, he still would not let Einstein's greatness be diminished in the slightest.
This experiment is easy to do and can produce results. It is much better than teacher Rutherford's unrealistic fantasy.
But he couldn't explain the twists and turns behind this to Cockcroft in detail, so he had to make up a few lies to fool him.
Deuterium is too expensive and is still a gas. Metal lithium is solid and convenient for experiments, etc.
It was a lie, but Chen Muwu was not lying. These were indeed the reasons why he changed his experimental ideas, but they were just part of them.
He encouraged, or rather encouraged with Cockcroft, that if we create the proton source one day earlier, we might be able to use protons to extract the electrically neutral particle that Director Rutherford has been thinking about from the lithium nucleus one day earlier. Blast it out.
But perhaps because he was too excited, Chen Muwu forgot that he had just prematurely told about using this experiment to verify the mass-energy equation.
This made Cockcroft a little confused. Isn't the purpose of replacing deuterium with lithium still to realize Rutherford's idea of bombarding electrically neutral particles from the nucleus?
What does this have to do with the mass-energy equation?
A few months later, after the experiment was finally completed, Cockcroft finally realized that, like Einstein, Dr. Chen also possessed the foresight of a genius.
Could it be that he had expected that this nuclear reaction would not produce electrically neutral particles, but would only emit two alpha particles?
…
Chen Muwu was doing experiments without any distractions at the University of Cambridge. However, outside Cambridge University, or in other words, except for his laboratory, a news report by Crowther caused a stir.
In the UK, this news was first published in the Manchester Guardian and reprinted in the Times and Daily Mail. This news appeared in the science section, and few editors would classify it in the current affairs section.
This is because the British media is also controlled by the government. The government does not allow excessive publicity about the strike and wants to treat the matter coldly.
Fortunately, because it is related to Cambridge University and the Cavendish Laboratory, it can also appear in the science and technology version.
But foreign media outside the UK don’t care about that much.
This kind of news worth several pounds, which is sent back to the country by transnational long-distance news cables by journalists based in London, will of course appear on the pages of foreign news!
The most famous school in the UK is Cambridge University.
The most famous laboratory in physics is the Cavendish Laboratory.
Two world-renowned physicists, one of whom, Chen Muwu, happened to be the cause of this news.
The director of the Cavendish Laboratory and the young talent Chen Muwu want to leave Cambridge University. No one will feel sorry for this amicable breakup that will hurt both sides, but they all want to get a piece of the pie.
One is an old physicist with both virtues and talents, and the other is a rising star in physics. The combination of the two can greatly improve the physics level of the school.
So in addition to the University of Göttingen, which had sent von Neumann as a guest in advance, universities all over Europe and the United States also took notice.
On the other side of the Atlantic in the United States, there are many universities that are not short of money and have long been eyeing Chen Muwu.
Former Cornell University President Shulman, who previously served as the U.S. Minister to China, resigned last year after his term expired. He is now the U.S. Ambassador to Germany and has contributed a lot to the implementation of the "Dawes Plan" .
Although it is difficult to obtain European news in China, during his tenure in China, Schulman always paid attention to news about Chen Muwu in English-language newspapers run by Westerners.
Of course, domestic English newspapers such as "Zi Lin Xi Bao" are also happy to report on Dr. Chen.
Because he is a kind of connection between China and Europe and the United States, and at the same time he is half a Haining, and he has an appetite for the upper-class Chinese intellectuals and compradors in the concession who can understand English.
After arriving in Germany from China, Schulman saw all kinds of detailed information about Chen Muwu from the old newspapers collected from the embassy and the new newspapers that were constantly delivered.
He increasingly felt that his failure to invite Chen Muwu to study at Cornell University was the biggest failure he had ever done while serving in China. It was even more failed than handling the Lincheng robbery on the Jinpu Railway. .
In his heart, Schulman once again remembered the Hu Shi who slapped his chest loudly and promised to send Chen Muwu to Cornell.
The kind of humility displayed by most Chinese people like Dr. Chen is not seen at all in him. He is just a stinker who loves to talk!
Fortunately, I saw in the newspaper that the Chancellor of Cambridge University, Belfort, was crazy and wanted to expel Chen Muwu from the school.
Shulman felt that Cornell's opportunity had finally arrived.
He immediately sent a message through the special telegram of the embassy in Germany to Livingston Farrand, who took over as principal after him, asking him to send the letter of appointment to Chen Muwu in Cambridge County as soon as possible no matter what method he used.
Connell's family is not the only one who likes Chen Muwu.
The president of Harvard University, Abbott Lowell, and the president of the University of California, Campbell, these universities that have had more or less contact with Chen Muwu, are also ready to give Chen Muwu an olive branch as soon as possible, just like Cornell University. .
Compton, a professor in the Department of Physics at the University of Chicago, who had never communicated directly with Chen Muwu and could only be regarded as a close friend for a long time, also ran to suggest to the department chairman Michelson that he should take this opportunity to invite Chen Muwu to the University of Chicago. .
Only by inviting Chen Muwu to Cambridge can the Department of Physics of the University of Chicago remain a leader in the United States despite the rapid rise in physics level at other universities.
Compton's words were somewhat presumptuous, and at first hearing, Michelson felt a little uncomfortable.
Oh, the physics department of the University of Chicago, where I, the first American Nobel Prize winner, sits, cannot maintain a stable position.
We have to invite China's first Nobel Prize winner here to be able to sit firmly on Diaoyutai, right?
Is this because foreign monks can chant sutras, or is it that the United States is not as good as Europe, but now it is not as good as China?
We must find some way to make America great again, MAGA!
However, after calming down, Michelson also felt that although Compton's words were a bit low-key, the central idea was still good. Dr. Chen was indeed different from others.
The achievements he made in just a few years at Cambridge would be enough to sustain an ordinary physics professor for a lifetime.
I am already very old, and I should consider retirement in two or three years. It is time to find a successor for the chairman of the physics department at the University of Chicago.
Professor Compton, whom he had originally intended to come to see him today, had mentioned this matter several times.
Compton knew that inviting Chen Muwu might cause him to lose his position as department chair, but he still insisted on inviting him. This is enough to show that he is sincerely interested in the development of the Chicago Physics Department.
But Michaelson thought of another question, which made him feel depressed for a moment after he was just happy.
"Arthur, I agree in principle to invite Dr. Chen to Chicago, but there is one other thing. I don't know if you still remember it.
“After Dr. Chen discovered Huangdi Star, the National Academy of Sciences planned to award him the Watson Prize.
“It should be very meaningful to award a prize named after an astronomer who once worked in China to a Chinese.
"But Dr. Chen quickly announced his refusal to accept the award after the news was announced. The reason for his refusal was not to resist our American colleagues, but to express his dissatisfaction with the restrictions imposed on his compatriots by refusing to enter the United States. Dissatisfaction with this restrictive immigration bill into the United States.
"I have thought before that if one day the gentlemen in Congress repeal this unreasonable bill, Dr. Chen might come to the United States to meet with us all.
"But not long after Dr. Chen discovered the new planet, our conservative and overly conservative President Coolidge signed a new and more stringent immigration law, aiming to exclude all Asian immigrants, even those who could participate in the "Washington Naval Treaty" "I, who outperformed France and Italy, are no exception.
"At this time, these politicians have completely eliminated Dr. Chen's hope of coming to the United States."
The reason why Michelson remembers this incident so clearly is that in addition to being a professor of physics at the University of Chicago, he is also the president of the National Academy of Sciences.
At that time, it was he himself who was going to award the Watson Award to Chen Muwu.
Michelson's words made Compton think deeply.
Being obsessed with academics, he only wanted to invite Chen Muwu to Chicago. He never thought there would be so many twists and turns behind it.
After a long while, Compton said: "Director, what do you think, we join forces with several other universities to put pressure on Congress and ask them to repeal this law for Dr. Chen?"
"As long as Dr. Chen can be invited to the United States, even if he is divided equally into three parts, so that he can spend four months in Chicago, four months at Harvard, and four months in California every year, it will be of great help to improve our physics level. .”
"Arthur, you are too naive. This bill was signed by President Coolidge. He will definitely not oppose himself."
"Director, maybe we can seek help from some other people. Secretary of Commerce Herbert Clark Hoover, it is said that this person is a dark horse in the current political arena and is very popular among voters.
“And he has experience working in China, so he must understand the unfairness of these bills.
"It is said that Coolidge will not run for president again after this term ends, and Hoover is the favorite to succeed the president.
"If we start with the Secretary of Commerce, use reason and emotion, convince him and ask him to come forward and propose to Congress to repeal the bill that is unequal to Asian immigrants, is this approach feasible?"
(End of chapter)
