Reborn and become a Great Scientist

Chapter 97 45 A New Isotope
After throwing the letter into the mailbox, Chen Muwu has been looking forward to de Broglie replying to him as soon as possible.

As long as he can get money from the little prince, he can continue the electron diffraction experiment.

If there is no money, Chen Muwu can only play lanterns with his nephew—as usual, he will continue to develop his fishing career in the Cavendish Laboratory.

However, the tree wants to be quiet but the wind keeps blowing. As soon as he returned to the Cavendish Laboratory in the morning, before the chair under Chen Muwu's butt was warm, Blackett came to him with a stack of photographic negatives that had already been developed.

In May, after he and Kapicha helped Chen Muwu find recoil electrons in the cloud chamber, Blackett continued to devote himself to the improvement of the cloud chamber.

Recently, he finally managed to improve Wilson's cloud room to a great extent on the basis of his predecessors.

Blackett only used simple mechanical structures such as levers, springs, and rotating wheels, which made the efficiency of the cloud chamber much higher than before.

Between the radiation source and the window of the cloud chamber, Blackett also installed a mechanical shutter device, which only puts the alpha particles into the cloud chamber when needed.

After his improvement, this cloud chamber system can basically take pictures automatically, counting from the moment when alpha particles enter the cloud chamber, an average of 13 seconds can complete a cycle.

Now that the efficiency of the cloud chamber has been greatly improved, Blackett began to use it to repeat the experiment of Rutherford's discovery of the proton countless times, and took many pictures at the same time.

The improved cloud room is good everywhere. The only inconvenience is that there are too many photos taken.

A photo can be produced every 13 seconds, so within an hour, nearly [-] photos can be taken.

After two or three days of experimentation, the photos can fill the entire table.

With only Blackett's ability alone, he can't see it at all.

So he could only hold a stack of photos, and asked Chen Muwu, who had failed the electron diffraction experiment and was in a panic in the laboratory recently: "Chen, you have nothing to do recently, can you help me read some negatives, and look for that one. The trajectory of the proton?"

It's not rude to come and go, he asked Blackett to help a lot before, and now that his good buddy found him, Chen Muwu had no reason to reject him.

He asked Blackett to put them all on the table, and he looked at them one by one.

There is a bunch of thin white lines on each photo, and the number is estimated to be more than 20.

And each thin white line represents the trail left by a charged particle in the cloud chamber.

Most of them are alpha particles passing through the cloud chamber, leaving a track that does not change the direction of motion.

A small part is the elastic collision between alpha particles and nitrogen atoms in the cloud chamber, resulting in two bifurcations.

Only a handful of alpha particles bombard the nitrogen nucleus and eject a proton, leaving few trails in photographs.

But what Blackett wants Chen Muwu to look for is the track left after the last collision.

Four years ago, Rutherford bombarded nitrogen nuclei with alpha particles and discovered that in this nuclear reaction, a new particle occasionally appeared.

After measuring the mass and charge of this new particle, Rutherford determined that this new particle is the nucleus H of hydrogen, or it can also be called the proton p.

In this regard, the explanation given by Rutherford is that the nitrogen nucleus is bombarded with alpha particles, and a proton is knocked out from it, and at the same time, the nitrogen on the target becomes carbon-13 (He+N→He+H+C).

He hadn't captured and observed this reaction from the cloud chamber, so he handed over the task to Blackett, who had just entered school at the time.

According to the explanation given by Rutherford, the trajectory in the photo should be divided into three forks after the collision, representing the bounced alpha particle itself, the proton ejected from the nitrogen nucleus, and the remaining particles after the proton was emitted. of atomic nuclei.

But the nuclear reaction that Chen Muwu remembered was completely different from the explanation given by Rutherford and Blackett.

Because after the alpha particle is incident, it is not bounced back at all, but is directly integrated into the nitrogen nucleus.

In this way, after the nucleus emits a proton, what becomes is not carbon-13, but oxygen-17 (He+N→H+O).

Therefore, there will be no three bifurcated trajectories in the photo at all. No matter whether protons are released or not, after the collision of alpha particles and nitrogen atoms, there will only be two bifurcated trajectories.

It's no wonder that Blake has a headache in the face of so many photos, because no matter how many photos he takes, he can't find any three-pointed trajectory in them.

But Chen Muwu was different. Knowing the real situation of nuclear reactions, he began to carefully identify the individual special cases in the two diverging trajectories that were obviously different from most of the others.

He helped Blackett look at the negatives for two days in the Cavendish laboratory, but found only one such trajectory among the large number of photos.

The past two days had already made Chen Muwu a little dizzy.

He didn't want to look for more tracks, but took this photo and came directly to Blackett.

Seeing Chen Muwu coming with the photo, Blackett was very surprised: "Chen, have you found the trajectory of that hydrogen atom, are you here to tell me the good news this time?"

"Yes, not all of them," Chen Muwu handed over the photo in his hand, "I found the trajectory of the proton, but the bifurcations of these trajectories are also two, not three as you said .”

"What does it mean?"

Blackett was very happy to hear that he had found the proton trajectory, but he still didn't understand the meaning of the second half of Chen Muwu's words.

Chen Muwu pointed to a trajectory on one of the photos and said: "Patrick, look at this trajectory. Although it has two forks like other collision trajectories, the forks here are different from others. .

"The first track is short and thick, and looks like the track of a nitrogen atom after a collision.

"But the second thin and straight track, which is obviously different from the post-collision alpha particle track, should be produced by a less charged and faster particle, and I think that's the proton you're looking for .”

"What does that mean?"

Blackett didn't react to Chen Muwu's explanation for a while.

Although the trajectory of the proton he mentioned does seem to be thinner and straighter than the trajectory of the alpha particle, but...

"Where do the alpha particles bounce off after being incident?"

He raised his doubts to Chen Muwu.

"It means that the reason why the alpha particle disappears is because it has not been bounced back." Chen Muwu pointed his finger on the short and thick particle track, "I just said that the track of this particle is like a nitrogen atom. But it did not say that it was a nitrogen atom. In this photo, not only was the process of nuclear transmutation recorded for the first time, but a new isotope was also photographed. I think the nucleus leaving this track is not carbon-13, but Oxygen-17."

(End of this chapter)