I Just Want to Be a Quiet Top Student

Chapter 80 Doppler Vanguard and General De Broglie

In fact, as early as the beginning of the 20th century, physicists noticed that light exerts radiation pressure on atoms. Because of the limitations of instruments and equipment, it was not until the invention of laser cooling devices in recent decades that the laser cooling technology of atoms was substantive. development of.

Mr. Zhu Diwen in Stanford’s laboratory used a three-dimensional laser beam to form a magneto-optical trap to trap atoms in a small area for cooling, and obtained a lower temperature optical adhesive. This was in 1985.

After more than ten years of painstaking research, Mr. Zhu and his scientific research partners went to the next level. They used this technology to obtain extremely low temperatures below the photon recoil limit. With this result, Mr. Zhu, Cohen Danokie, and Phillips won the Nobel Prize in Physics at the same time. It was 1997.

After more than ten or two decades into the 21st century, in the laboratory of Nangang No. 2 Middle School, Mr. Mu posed a question based on the research results of the Nobel Prize in Physics: “In the laser cooling experiment of atoms, the recoil effect is considered. , What is the minimum value of temperature?”

All the students under the stage scratched their heads and scratched their heads: “Teacher Mu, we are just high school students. With this insight, we won’t win the Nobel Prize?”

Only Shen Qi was silent. He understood the meaning of Teacher Mu’s question. She didn’t expect any high school student to have the level of Nobel Prize.

This question is about laser transmitters and atom trapping. At first glance, it seems extremely high-end. In the final analysis, the laser cooling experiment of atoms is a verification of the theoretical assumptions of Doppler and De Broglie, and it has been carried forward and gradually improved.

In high school physics textbooks, high school students learn about the Doppler effect, de Broglie waves, the wave-particle duality of light, the Bohr energy level model, alpha particle bombardment, and basic theories of atomic electrons. Of course, these are the most difficult parts of high school physics.

Shen Qi has learned the big things by himself, and the obstacle to his understanding is relatively small.

As far as problem-solving is concerned, if you are not proficient in the necessary mathematical tools (formulas, inferences, theorems, etc.), you will be helpless to solve the corresponding mathematical problems, and physics problems are more progressive in understanding. Calculate in small amounts.

“This does not require Nobel Prize-level brains, you only need to have physics competition-level brains.” Teacher Mu smiled and asked: “Do you think this question is difficult?”

“difficult!”

“IPhO’s medium-difficulty test questions, or CPhO national finals theory test questions, are almost at this level of difficulty.” Teacher Mu scanned the stage for the next week and said: “Know that when you participate in the competition, no one will show you a teaching video. Less than 3D demo animation, the only clue is the schematic plan view on the roll surface. Now, it is similar to the plan view on the screen. So I played the animation for you, and I played it twice, and I gave you simultaneous explanations. You shouldn’t show it. Curious about the baby’s ignorant expression. Future physicists, come up with something real, please don’t let me down.”

The audience was silent for a moment.

The level of the players of the 　　 material competition team is naturally not too bad, and it is not only Shen Qi who has self-taught electives or part of the knowledge of major objects.

All the members of the 　　 material competition team picked up their pens and immersed themselves in writing and drawing on the draft, deriving calculations.

Shen Qi didn’t bring a pen or paper. He came empty-handed, staring at the two-dimensional schematic diagram of the atomic reference system on the screen, thinking about something.

“Brother, you can’t figure out the minimum temperature value mentally, right?” Lin Xingyu wrote and found that Shen Qi beside him was sitting steady like a mountain with arms folded.

“Mental arithmetic? It doesn’t exist.” Shen Qi shook his head and opened his palm: “Pen.”

Lin Xingyu’s pencil case contained a pile of pens, and he took out one of the most expensive water-based pens and handed it to Shen Qi.

“Paper comes.” Shen Qi spread his palms again.

sizzle.

Lin Xingyu tore a page from his draft and handed it to Shen Qi.

Thinking that one page of draft paper shouldn’t be enough, Lin Xingyu tore a few sheets in a row.

“One piece of draft paper is enough.” Shen Qi waved his hand, holding a pen to deduce on the draft paper.

In this atomic laser cooling experiment, the minimum temperature value must be calculated. The calculation is not large, but the derivation steps are relatively cumbersome. Shen Qi must draft a draft, and the scale must be properly grasped according to the actual situation.

Brush brush.

Shen Qi flew his pen, and quickly filled both sides of the draft paper.

“Whhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.

Teacher Mu noticed Shen Qi: “It seems that Shen Qi has got results?”

Snapped.

Shen Qi snapped his fingers: “Yes.”

Happiness.

Teacher Mu’s left and right hands snapped his fingers: “Then please show your results, Shen Qi.”

Cleaned up the submarine question on the blackboard. Teacher Mu asked Shen Qi to come to the stage to answer.

Shen Qi came to the stage and took a piece of chalk and wrote on the blackboard.

The first step of this problem is to get the frequency of the laser. According to the classic Doppler effect, we can get:

Ω(1+vx/c)

In fact, it is impossible for Doppler himself to realize that the theoretical effect he put forward at a flash of time will be widely used in various countries and fields around the world after one or two hundred years.

Today’s color Doppler effect in hospitals is based on the Doppler effect, which is also widely used in the military, as well as at the atomic microscopic level.

Shen Qi ordered Doppler to open an exit for the vanguard. Combined with the topic setting, the Doppler vanguard entered the enemy camp and conducted a surprise attack.

If the electron blasts towards us at a positive velocity v, a backward movement can be obtained, and the horizontal size of the entire figure will be reduced by the ratio of c-v to c.

Shen Qi can calculate an electric field after taking the second derivative. When high-energy electrons pass through, they emit radiation in the forward direction. This is Bremsstrahlung. The output of the Doppler Pioneer ends here, and he completed what Shen Qi gave. Mission Next it is General De Broglie’s turn.

de Broglie wave has actually involved the preliminary quantum mechanics. The high school physics textbooks are not general, but the essence is written in the textbooks, but there are more conclusive descriptions and fewer specific explanations.

Shen Qi commanded General De Broglie’s Ma Ta company to camp. He gave the momentum of the atom to absorb a photon on the blackboard as:

?Ω0/c

When the temperature is assumed to be T, the corresponding de Broglie wavelength is:

Λ=?/root sign mkT

Wave number is the rate of change of phase versus distance, and frequency is the rate of change of phase versus time. ω and k are similar to time and space in a spatial direction.

Mr. Zhu Diwen uses a three-dimensional laser beam to form a magneto-optical trap to trap atoms in a small area to cool them. The 3D animation that Mr. Mu just played simply simulates this experimental process. The propagation of light in three-dimensional space interacts with atoms and absorbs The number of atoms after the photon, and the momentum generated by each absorption and radiation of the atom surface…Shen Qi filled the blackboard on the left, and the solution process was nearly half completed.

Teacher Mu kept a wait-and-see attitude, and Lin Xingyu in the audience had the draft written by Shen Qi just now in front of him.

Lin Xingyu looked down at Shen Qi’s draft, and looked up at the solution process on the blackboard. This is not right. Shen Qi’s draft is different from what he wrote on the blackboard.

Lin Xingyu can basically understand more than half of the content on the blackboard, but when he looks at Shen Qi’s draft paper, he can’t understand at all.

Because what Shen Qi writes on the draft paper are relatively independent core steps, his thinking is too leap, and few people except him can understand what he wants to express.

Shen Qi uses the core steps as a guideline, and starts a detailed solution on the blackboard. Soon, the answer will come out soon.