After throwing the letter into the mailbox, Chen Muwu had been hoping that De Broglie would reply to him as soon as possible.

As long as he can get money from the little prince, he can continue to carry out experiments on electron diffraction.

If he didn't have the money, Chen Muwu would have to make lanterns with his nephew - as usual, and continue his fishing career in the Cavendish laboratory.

However, the tree wanted to be quiet and the wind did not stop, and as soon as he returned to the Cavendish laboratory in the morning, the chair under Chen Muwu's ass was not yet hot, and Blackett approached him with a stack of photographic negatives that had been washed.

In May, after helping Chen Muwu find the recoil electron in the cloud room with Kapitsa, Blackett continued to devote himself to the improvement of the cloud room.

Recently, he has finally succeeded in making a great improvement on the Wilson Cloud Room on the basis of his predecessors.

Blackett used only a simple mechanical structure such as levers, springs, and rotating wheels to make the cloud chamber much more efficient than before.

Between the source and the window of the cloud chamber, Blackett also set up an additional mechanical shutter device, and only when necessary, will alpha particles be placed into the cloud chamber.

After his improvement, this cloud room system can basically take pictures automatically, counting from the moment the alpha particles enter the cloud room, on average, every thirteen seconds, it can complete a cycle.

Now that the efficiency of the cloud room had increased dramatically, Blackett began to use it to repeat Rutherford's experiment with discovering protons countless times, as well as taking many photographs.

After the improvement of the cloud room, everywhere is good, the only inconvenient place is only one, that is, there are too many photos.

A photo can be produced every thirteen seconds, so in an hour, nearly 300 photos can be taken.

After two or three days of experimentation, the whole table can be filled with pictures.

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

So he could only hold a stack of photos, and the electron diffraction experiment failed, and Chen Muwu, who had been idle in the laboratory recently, begged: "Chen, you haven't had anything to do lately, can you help me look at some negatives and find the trajectory of that proton?" ”

Come and don't be rude, he has asked Blackett to help a lot before, and since his good buddy has found him, Chen Muwu has no reason to refuse him.

He asked Blackett to put them on the table and look 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 twenty.

Each thin white line represents the trajectory left by a charged particle in the cloud chamber.

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

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

Only a handful of alpha particles can bombard the nucleus of a nitrogen atom and then shoot out a proton, so the trajectories left on the photograph are rare.

But what Blackett wanted Chen Muwu to look for was the trajectory left behind after the last kind of collision.

Four years ago, Rutherford bombarded the nucleus of nitrogen with alpha particles, and found that in this nuclear reaction, a new particle occasionally appeared.

After measuring the mass and quantity of the new particle, Rutherford determined that the new particle was the nucleus H of hydrogen, or proton p.

Rutherford's explanation for this is that the nitrogen nucleus is bombarded with alpha particles, from which a proton is struck, 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 room, so he gave the task to Blackett, who had just entered school at the time.

If Rutherford gives this explanation, then the trajectory in the photograph should be divided into three prongs after the collision, representing the alpha particle itself that is bounced back, the protons ejected from the nitrogen nucleus, and the nucleus that remains after the emission of the protons.

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

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

In this way, when a proton is emitted from the nucleus, it does not become carbon-13, but oxygen-17 (He+N→H+O).

So there are no three bifurcated trajectories in the photo, whether protons are released or not, and after the collision of alpha particles and nitrogen atoms, only two bifurcations will be produced.

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 a single trace of the fork in them.

But Chen Muwu was different, knowing the real nuclear reaction, and he began to carefully identify the two bifurcated trajectories that were distinctly different from most of the other exceptions.

He helped Blackett look at the negatives in the Cavendish lab for two days, but found only one such trail from a large number of photographs.

The past two days have made Chen Muwu a little dizzy.

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

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

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

"What does that mean?"

Hearing that he had found the proton track, Blackett was very happy, but he didn't understand what Chen Muwu meant by the second half of his words.

Chen Muwu pointed to a trajectory on one of the photos and said: "Patrick, look at this trajectory, although it is the same as other collision trajectories, it produces two bifurcations, but the bifurcation here is a little different from the others.

"The first trajectory is short and thick, and it looks similar to the trajectory of a nitrogen atom after a collision.

"But this second thin and straight trajectory, which is significantly different from the trajectory of the alpha particle after the collision, should be produced by a particle with less charge and high velocity, and I think that's the proton you're looking for."

"What does that mean?"

Regarding Chen Muwu's explanation, Blackett did not react for a while.

Although the trajectory of the proton he is talking about does appear to be thinner and straighter than that of the alpha particle, it ......

"Where do the alpha particles that bounce back after incident go?"

He raised his question to Chen Muwu.

"That is to say, the reason why the alpha particle disappears is because it is not bounced back," Chen Muwu pointed his finger at the short, thick particle trajectory, "I just said that the trajectory of this particle resembles a nitrogen atom, but I didn't say that it is a nitrogen atom." In this photo, not only is the process of nuclear transmutation recorded for the first time, but also a new isotope is captured, and I think that the nucleus that left this trajectory is not carbon-13, but oxygen-17. ”

(End of chapter)