1900: A physics genius wandering around Europe

Chapter 690 A Powerful Declaration! Slower Than Faster! Unwavering Confidence in Victory! How exactly was transuranic element determined?
The highest meeting of the Pangu Project lasted a full day.

The concept of nuclear chain reaction is truly astonishing.

Qian Wushi, Yu Yin, and others had too many questions about the details.

However, Riggi cannot speak too far ahead for now; everything must wait until the dust settles on uranium nuclear fission.

"Therefore, next year's Rome nuclear physics conference is extremely important."

"Perhaps there will be a final conclusion regarding uranium nuclear fission and transuranic elements."

"At that time, Yu Yin and Huai Ning, you two will go to attend the meeting."

The two men immediately accepted the order, their expressions excited.

After hearing the dean's groundbreaking idea, their focus on transuranic elements reached its peak.

It is crucial to the Pangu Project.

Finally, Li Qiwei said:
"Everything discussed at today's meeting is highly confidential and must not be disclosed."

"Although I have been planning ahead for many years, in terms of national strength, we are still no match for countries like Britain, France, Germany, and the United States."

"The principle of nuclear chain reaction is very simple, but to actually achieve it is probably not easy. We need to be mentally prepared."

"This time, we must seize the opportunity! To revitalize China!"

Wow!
Everyone was shocked and nodded solemnly.

This is a glimmer of hope that the dean won for China with his extraordinary wisdom!
No room for error!

However, Xia Yuanli, who had been silent all along, suddenly spoke up:
"Dean, can this secret really be kept?"

Wow!
Everyone looked at him.

What does it mean?
Xia Yuanli looked at everyone and said:

"I'm probably the worst person there."

"But even so, I can understand nuclear chain reactions."

"Don't those top physicists think of this?"

"I am not questioning the dean's authority."

"Instead, I felt that this was not a breakthrough in basic science, but rather a detail in technology."

"So even if we don't leak the secret, someone will probably figure it out on their own."

hiss!
After hearing this, everyone fell silent.

They did not refute Xia Yuanli.

Especially Qian Wushi, Yu Yin and others, they were full of self-confidence.

If someone tells them that uranium can undergo nuclear fission, they could invent a weapon.

The two of them probably also thought about nuclear reactions.

Although they couldn't immediately imagine that one neutron could collide and create two neutrons.

But this kind of thing should be able to be determined quickly through experiments, so it's not a difficult point.

To put it bluntly, the entire research process on transuranic elements is currently at the level of "technology" rather than the level of "principle".

Li Qiwei was deeply moved upon hearing this.

There was no dissatisfaction on his face; instead, he looked at Xia Yuanli with satisfaction.

Once upon a time, he aspired to be the sole nuclear power, monopolizing the development of nuclear weapons.

However, the more he interacted with those historically renowned figures, the more he felt that this idea was unreliable.

This is a real world, and nobody is a fool.

So he changed his strategy.

From "having what others don't have" to "being fast when others are slow".

He has everything ready, except for the final push.

He was able to avoid all the pitfalls that occurred during the research and development process.

Ridgway was even confident that he could create an atomic bomb in a year and a half.

When everyone is still uncertain about the prospects and difficulties of nuclear weapons, it is better to strike first.

In real history, Oppenheimer's team of theoretical physics practitioners was concerned about one issue:
"What if the nuclear chain reaction gets out of control and causes nuclear fission to occur in every element on Earth?"

That would have blown the Earth to smithereens.

Later, someone did the calculations and found that it was indeed possible, but the probability was extremely low.

Oppenheimer and others struggled with this decision for a long time.

At this moment, facing the group, Li Qiwei said domineeringly:

"There is never a plan that guarantees victory in this world."

"But I am confident of victory!"

Wow!
Everyone was thrilled!

Time flies, and it was 1929 in the blink of an eye.

The controversy surrounding transuranic elements has not subsided; on the contrary, it has become even more perplexing due to various "strange" phenomena.

Researchers have discovered seven or eight new elements in the products of neutron bombardment of uranium.

Moreover, these elements are all below the uranium level.

Of course, very few people can confirm what these elements actually are; most of it is just guesswork.

Some people might find it strange:
"It's just a few elements, isn't it?"

"Why can't so many top researchers analyze this?"

There are two main reasons.

First, the product content is too low.

In later generations, even a small sample of a substance will be able to be quickly analyzed using instruments to determine its composition.

However, in this era, it is not that advanced.

Although mass spectrometers capable of distinguishing isotopes have emerged, they have high requirements for the samples.

Therefore, researchers can only use the methods mentioned earlier to analyze the data bit by bit.

Second, the products are complex.

Later researchers replicated this experiment of bombarding uranium with neutrons.

Detection using ultra-high precision instruments revealed that neutron bombardment of uranium in this era produces products containing nearly 300 isotopes of at least 30 elements.

In other words, uranium nuclei produced all elements from barium (element 56) to protactinium (element 91), and each element had several isotopes.

Such a terrifying quantity is a nightmare for chemical analysis.

Most physicists are not good at separating elements, so they feel helpless.

Even experienced chemists find it a headache.

Kaiser Wilhelm Institute for Chemistry, Germany.

Hahn finally succeeded Haber as the new director.

Therefore, he had more power to ensure research on transuranium elements.

Moreover, he defied public opinion and gave Meitner a good salary, which caused quite a stir in the institute.

In real history, Hahn ultimately betrayed Meitner, claiming sole credit for the discovery of uranium fission, and the Nobel Prize was awarded solely to him.

However, he himself refused to participate in Germany's weapons development projects.

He even publicly stated:

"I hope that all physicists will never study the uranium bomb."

"If Hitler ever gets his hands on such a weapon, I will commit suicide."

However, while Hahn did eventually work on the atomic bomb, he did not commit suicide.

"No, it wasn't me! Don't talk nonsense! I was talking about a uranium bomb, not an atomic bomb."

Therefore, judging from these events, Hahn's initial coldness towards Meitner was probably for his own self-preservation.

Under such high pressure, some human behaviors cannot be measured by common sense.

Scientists are human beings too, and they also have human emotions and desires.

Life, friendship, morality, country.
These things are intertwined in a tangled mess, and if a person has been conflicted about them, it means they are not entirely bad. At this point in time, although the atmosphere in Germany is tense, it has not yet reached an uncontrollable state.

Therefore, the friendship between Hahn and Meitner did not break down.

Because of Li Qiwei, the former treated the latter even better.

After all, everyone knows that Professor Bruce is a staunch advocate for women's rights, and he pays particular attention to the rights of female scientists.

Hahn needs to be mindful of this if he wants to stay in the industry.

On this day, the trio was holding an internal debriefing meeting.

Hahn said:

"We have now discovered 12 unknown isotopes in the products of neutron bombardment of uranium."

"But we have never been able to obtain the real element 93."

After speaking, he looked at Strassmann, who, although only his assistant, was also a core member of the team.

It was thanks to the other party's superb chemical skills that they were able to quickly separate the different isotopes.

But light separation is useless; analysis is still required.

Meitner said:
"Currently, we identify elements mainly based on their half-life."

"If the half-life is the same as that of a known element, then it's easy to confirm."

"But if they are different, it is difficult to determine whether it is a transuranic element or an isotope of a known element."

After Meitner finished speaking, Hahn and Strassmann both nodded helplessly.

Elena's pioneering method of half-life analysis is very useful.

But the shortcomings are also obvious.

The half-lives of different isotopes of the same element can vary greatly.

For some, it might take a few days; for others, it might take millions of years.

Therefore, once a new half-life appears, it is difficult to be certain that it is a transuranic element.

Strassmann said:
"I'll go check the information again and improve the analysis process."

Hahn and Meitner nodded with smiles.

"Thanks a lot."

At this point, Strassmann offered another suggestion:

"I think we can try to replicate the Curies' experiment."

"They used lanthanum as a precipitant, which can precipitate transuranic elements."

"Then could we consider using barium as a precipitate as well?"

Wow!
After hearing this, Hamai and his companion had a sudden inspiration.

That's one direction we could be heading.

They plan to begin preparations for new experiments, aiming to achieve breakthrough results before this year's nuclear physics conference!
However, what the two did not know was that Strassmann's words had led everyone astray.

At this point, some people might be wondering:

"Since transuranic elements are so difficult to analyze, how did McMillan determine them?"

In real history, in 1939, McMillan used a cyclotron to conduct experiments bombarding uranium with neutrons.

Because he could control the speed of neutrons, he quickly obtained results that differed from those of others.

He discovered a new element with a half-life of 2.3 days in the bombardment products.

This is unlike any data we've seen before.

However, McMillan also didn't know whether it was a true transuranic element or an isotope of some known element.

So he asked his colleague, Albertson, to help analyze the data. Albertson was also Lawrence's doctoral student and had just graduated that year.

Abelsen double majored in physics and chemistry during his undergraduate studies, giving him a very solid foundation.

He was very familiar with the history of transuranic elements and knew that the only way to finally confirm them was through chemical methods.

So he had a sudden inspiration: instead of separating pure transuranic elements, he would directly measure their chemical properties.

So, what property is the most intuitive?
Of course, it refers to the valence and color of substances.

As is well known, in flame tests, different elements exhibit different colors when burning.

Similarly, when a substance is dissolved in a solution, it will also exhibit different colors.

Moreover, even the same element can have different colors if its valence is different.

Based on this idea, Abelsen experimented with various acids, such as hydrochloric acid, sulfuric acid, and nitric acid, to dissolve the substances prepared by Macmillan.

After a series of experiments, he finally discovered that fluorine-containing nitric acid had the best solubility for this element.

So he began to focus on experiments with fluorinated nitric acid, adjusting the valence of this unknown element by changing its concentration.

In 1940, Abelsen's experiments finally yielded a groundbreaking discovery.

He discovered that this new element has five oxidation states, each with a different color.

3价为紫色、4价为黄色、5价为蓝绿色、6价为粉红色、7价为深绿色。

This correspondence between valence and color is unique to this element and is not found in any other known element.

Therefore, Eberson was able to conclude that the new element discovered by McMillan must be the transuranium element that everyone had been searching for.

Now, only one question remains.

Is it element 93 or element 94?

With the experience gained above, Ebersen conducted a more in-depth study of the properties of this transuranium element.

He discovered that a trace amount of the pure substance could be obtained by reducing the trifluoride of this substance with barium vapor at 1200°C.

This is a silvery-white metal.

Once you have pure metal, the measurement becomes much simpler.

Its atomic number can be quickly determined to be 93 using physical methods.

That is, the element discovered by Macmillan is element 93.

With this, the story of transuranic elements officially comes to an end.

Incidentally, it was during his research on the chemical properties of transuranic elements that Ebersen discovered uranium hexafluoride, a volatile liquid.

Uranium hexafluoride molecules containing uranium-235 are 1% lighter than those containing uranium-238.

Therefore, if a portion of the gas volume is heated, the lighter molecules tend to concentrate in the heated area.

Based on this principle, he proposed a completely new method for uranium-235 separation: thermal diffusion.

As mentioned earlier, the United States simultaneously employed three uranium separation methods during the Manhattan Project.

Lawrence was in charge of the electromagnetic method, Yuri was in charge of the gas diffusion method, and the last one was Ebersen's thermal diffusion method!

This demonstrates their strength.

Of course, his thermal diffusion method was eventually abandoned due to efficiency issues.

At this point, some people might be curious:
"No, the author!"

"Where's the centrifugation method we often hear about? Why isn't it mentioned?"

"Isn't centrifugation the most energy-consuming method?"

Misunderstanding! It's all a misunderstanding!
We'll discuss this later.

In short, Ebersen's work opened up new avenues of thought for later researchers, making it easy to analyze the nature of elements, starting with element 94.

Later, even more sophisticated instruments emerged, allowing the analysis of characteristic radiation to determine the element number even if only a few atoms were produced.

For example, researchers at Berkeley hung a bell on the instrument, and when the instrument detected the characteristic radiation, the bell would ring.

At this point, everyone knew that a new element had been born!
At this moment, Strassmann clearly hadn't thought of this yet.

However, in another sense, without his and Elena's various failures, Eberson might not have been able to come up with a new approach.

This is the process of scientific accumulation.

However, transuranium elements are difficult to identify, while known elements are easy to identify.

Soon, a cataclysmic earthquake will shake the physics community!

(End of this chapter)