In fact, as early as the beginning of the 20th century, physicists noticed that light has a radiant pressure effect on atoms, because of the limitations of instruments and equipment, until the invention of laser cooling devices in recent decades, the laser cooling technology of atoms has been substantially developed.

In 1985, Steven Chu used a three-dimensional laser beam to form a magneto-optical trap to trap atoms in a small area and cool them to obtain a lower temperature optical adhesive in 1985.

After more than a decade of painstaking research, Mr. Zhu and his research partners took it to the next level, using this technique to achieve extremely low temperatures below the photon recoil limit. With this achievement, Mr. Zhu, Cohen-Danokee and Phillips were awarded the Nobel Prize in Physics in 1997.

After another ten or twenty years into the 21st century, in the laboratory of Nangang No. 2 Middle School, Professor Mu made a question based on the research results of the Nobel Prize in Physics: "In the laser cooling experiment of atoms, considering the recoil effect, what is the minimum value of temperature?"

The students in the audience scratched their ears and cheeks: "Teacher Mu, we are just high school students, we won't win the Nobel Prize with this brainhole?"

Only Shen Qi was silent, he understood Teacher Mu's question, she didn't expect any high school student to have the level of the Nobel Prize.

In the final analysis, the laser cooling experiment of atoms is a verification of the theoretical hypotheses of Doppler, de Broglie and others, 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, wave-particle duality of light, Bohr level model, α particle bombardment, basic theory of atomic electrons, etc. Of course, these are some of the hardest things to understand in high school physics.

Shen Qi had already learned big things on his own, and the obstacles to his understanding were relatively small.

In terms of problem solving, if you are not proficient in the necessary mathematical tools (formulas, corollaries, theorems, etc.), you will be helpless to solve the corresponding mathematical problems, while physics problems are more of a progression in understanding, supplemented by a small amount of calculations.

"You don't need a Nobel Prize-level brainstorm, you just need to have a physics competition-level brain. Teacher Mu smiled and asked, "Do you think this question is difficult?"

"Difficult!"

"IPhO's medium-difficulty questions, or CPhO theory questions, are about that level of difficulty. Mr. Mu glanced at the audience for a week and said, "You must know that when you participate in the competition, no one will show you a teaching video, you can't see the 3D demonstration animation, and the only clue is the plane diagram on the scroll." Well, it's like this floor plan on the screen. So I played you the animation, broadcast it twice, and explained it to you at the same time, you shouldn't show the ignorant expression of a curious baby. Future physicists, come up with some real skills, and please don't let me down. ”

The audience was silent for an instant.

The level of the players of the competition team is naturally not too bad, and Shen Qi is not the only one who has taught himself electives or some big things.

All the members of the competition team picked up the pen, buried their heads in the sketchbook, wrote and drawn, and deduced calculations.

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

"Brother, you can't calculate the minimum temperature value by heart, right?" Lin Xingyu wrote, and found that Shen Qi beside him was sitting firmly with his arms folded.

"Mental arithmetic? Shen Qi shook his head and spread out his palm: "Come to the pen." ”

Lin Xingyu's pencil case contained a bunch 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 off a page from his sketchbook and handed it to Shen Qi.

Thinking that a page of scratch paper should not be enough, hiss, Lin Xingyu tore a few sheets in a row.

"A piece of scratch paper is enough. Shen Qi waved his hand and held a pen on the scratch paper to derive.

In the laser cooling experiment of this atom, the minimum temperature value is not large, but the derivation steps are more cumbersome, Shen Qi must make a draft, and pretend to be forced to properly grasp the scale according to the actual situation.

Brush brush brush.

Shen Qiyun's pen flew like a fly, and soon filled the front and back of the scratch paper.

"Whew...... I see. Shen Qi raised his head and breathed a sigh of relief, twisted his neck, and it was done.

Teacher Mu noticed Shen Qi: "It seems that Shen Qi has already achieved results?"

Syllable.

Shen Qi snapped his fingers: "There is." ”

Smack.

Teacher Mu snapped his fingers with his left hand and right hand: "Then please show Shen Qi your results." ”

Wipe the submarine question on the blackboard just now, and Mr. 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 in this problem is to first obtain the frequency of the laser, which can be obtained according to the classical Doppler effect:

ω（1+vx/c）

In fact, Doppler himself could not have realized that the effect of the theory he proposed on a flash of inspiration was widely used in various countries and fields around the world one or two hundred years later.

Today's color ultrasound 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 officer, and combined with the topic setting, the Doppler vanguard officer entered the enemy camp and carried out a surprise attack first.

If the electrons blast towards us at a positive rate v, we can get a backward motion and the transverse size of the whole graph will be reduced in the ratio of c-v to c.

After Shen Qi takes the second derivative, he can calculate an electric field, and when the high-energy electrons pass through, they emit radiation in the forward direction, which is bremsstralier radiation, and the wave of output of the Doppler pioneer officer ends here, and he completes the task assigned by Shen Qi.

It was next General de Broglie's turn to step forward.

De Broglie's wave has actually touched on the preliminary quantum mechanics, and the high school physics textbooks are not general, but the textbooks write the essence, but there are many conclusive descriptions and few specific explanations.

Shen Qi ordered General de Broglie to step into the battalion, and he gave on the blackboard the momentum of an atom absorbing a photon as:

ћω0/c

Assuming that the temperature is T, the corresponding de Broglie wavelength is:

λ = ћ/root number mkT

The wavenumber is the rate of change of phase versus distance, the frequency is the rate of change of phase versus time, and ω and k are similar to time and space in one spatial direction.

Mr. Steven Chu uses a three-dimensional laser beam to form a magneto-optical trap to trap atoms in a small area space for cooling, and the 3D animation just played by Mr. Mu simply simulates this experimental process, the propagation of light in three-dimensional space and the interaction of atoms, the number of atoms after absorbing photons, and the momentum generated by each absorption and radiation of atoms surface...... Shen Qi wrote all over the blackboard on the left, and the solution process was nearly halfway complete.

Teacher Mu remained silent and wait-and-see, and Lin Xingyu in the audience had the draft that Shen Qi had just typed in front of him.

Lin Xingyu looked down at Shen Qi's draft, 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 most of the content on the blackboard, and then look at Shen Qi's scratch paper, he can't understand it at all.

Because Shen Qi wrote relatively independent core steps on scratch paper, his thinking was too jumpy, and few people except himself could read what he wanted to express.

Shen Qi took the core steps as the program, and carried out a detailed solution on the blackboard, and the answer was about to come out.