In the midst of the doubts, surprises and incredulity of the Fuso people, the first identification test began.

Everyone changed their clothes, sanitized them, and then entered a clean room.

After entering the clean room, most people can still only watch through a glass outside, and only a few museum staff and sampling personnel can walk to the innermost National Treasure Storage Room.

Gu You, Director Shi and Director Ning (chairs of the Department of Archaeology at HKUST) sat on the sidelines talking and laughing freely, watching Professor Yamashita of Kyoto University through bulletproof glass and taking samples with the students.

Professor Sakai of the University of Tokyo looked through the original Chinese experimental records to make sure that the identification samples would not be wasted for a while.

On the Fuso side, the number one expert in the identification of C14 isotope abundance is this Sakai professor. If he did not nod, the Chinese side would not be able to obtain the unearthed stain samples on the "Seal of the Han King" to carry out the experimental operation.

I saw Professor Yamashita and his students first use a laser spectrometer to scan the "Seal of the King of the Han Dynasty" through the glass cover filled with helium inside.

It is a pure gold seal with a size of only 2.3 centimeters square, and the museum is accustomed to maintaining a low-light environment all year round and reducing the annual exposure of the collection, so it is almost difficult for people outside to see the operation clearly.

In fact, gold products are not afraid of exposure. The main reason for reducing the exposure of museums is to protect organic matter such as calligraphy and painting, which are prone to aging and degradation.

However, it is inevitable that there are substances that are afraid of exposure among the stains and other attachments from the unearthed year on the outside of the gold products, so it is always a good idea to be careful with the protection of the gold products.

Moreover, in the C14 abundance identification experiment, the key is these stains and adherents from the soil layer.

Because the gold seal is theoretically Au elemental. Even if the ancient craftsmanship is not perfect, and some carbon elements are mixed in the gold seal in a single form, it is impossible to cut and destroy the gold seal itself for the purpose of sampling, so to obtain a sample with more carbon elements, it is necessary to start with the soil layer stain.

(Another advantage of stamps is that the stained ink contains carbon.) In addition to cinnabar, a certain amount of vegetable oil/plant flavor is added, which contains cellulose, which can be used as a material for the identification of C14 isotope abundance. ）

Professor Yamashita first determined that there were mainly a few carbon-rich stains on the surface of the gold seal, and then he did a lot of work, and in a nutshell, he took the sample off and put it in an absolutely clean, carbon-free sampling container. After another operation, the carbon atom cluster was extracted.

These specific experimental processes were busy for about an hour, so I won't go into details—because there is nothing new in them, and in the traditional centrifugal method of C14 isotope abundance identification, the operation is the same up to this step.

The difference between centrifugation and ion-accelerated mass spectrometry will be reflected in the subsequent links.

"Shi Sang, this is a group of carbon atoms extracted from the ink clay part, and the subsequent operation is up to you. Professor Yamashita said, handing the special container to the Chinese personnel.

The contents are estimated to be only a few milligrams, and they should be the carbon in ancient vegetable oils and fibers extracted from the ink.

Deputy Director Shi didn't dare to answer, but just made a gesture to Gu Wan. Gu Wan took it over, and then with the help of Deputy Director Shi and other assistants, he began to operate the AMS.

Of course, the internal activities of the instrument cannot be seen macroscopically, all in all, after more than half an hour, Gu Yu got an output data, and then calculated it on the special software.

"According to the measurement, the ratio of C14 to C12 in the sample is about 1 in 1,520 billion, which is about 0.338 half-lives in the standard ratio of 1 in 1.2 trillion parts. Therefore, it can be preliminarily determined that the year of the ink on this sample is about 1940, and the positive and negative error is 20 years. ”

Gu Wan first said the conclusion succinctly.

Laymen may be a little confused when they hear it, but the people present are all university professors, and they are all counterpart majors such as archaeology and atomic physics, so they naturally understand it as soon as they hear it.

The rest is only doubts about the accuracy of the measured data. As for the conversion of the data, there is no doubt that everyone knows the formula well.

As we all know, during the survival of any living organism, the carbon in the organic matter that makes up its body will be constantly metabolized, so the ratio of C12 and C14 in carbon should be the same as the average ratio of C12 and C14 in nature, about 1.2 trillion times.

That is, if you have a total of 1,200,000,000 carbon atoms in a piece of meat, then 1,200 billion of them are C12 and only 1 is C14.

After the death of the living organism, there will be no metabolism to replenish carbon, so the C14 buried in fossils and bones will only become less and less.

According to high school chemistry knowledge, the half-life of C14 is 5730 years, that is, after 5730 years, the C14 in the dead body will be reduced by half, and the ratio of C12 to C14 will become 2.4 trillion times. After 11,460 years, it will be reduced to a quarter of the initial state, that is, 4.8 trillion times......

The accuracy of dating can be as short as about 30 years, which is equivalent to 5730 years of natural half-life, divided by 2 to about 8 power. Therefore, the change in C14 abundance that can be measured should be roughly equivalent to 2 times the number of eight root openings.

For example, when the analyte is dated to 1910, the concentration of C14 should be only 79.4% of the fresh state, and when it is 1940, the concentration of C14 should be only 79.1% of the fresh state.

Considering that in the natural state, C14 is only 1.2 trillion parts of C12, so his instrument can basically reach the level of "every 400 trillion carbon atoms, one less C14 atom can be measured".

Don't exaggerate, the ion accelerator mass spectrometers on the earth in the 21st century can also be measured so accurately.

It may be unimaginable to the layman, but the physical technology of modern human beings has really reached this level.

……

Professor Yamashita of the Department of Archaeology at Kyoto University is not very proficient in physics after all, so he only knows the above principles and algorithms.

However, the reliability of the measurement of the data itself is up to Professor Sakai of the Department of High Energy Physics at Tokyo University to decide.

If this measurement itself is reliable, it means that it can be proved that the "seal of the Han and Japanese kings" is something before 1940 (plus or minus error of 20 years).

The Sakai layman looked at the data report, touched his chin and thought for a while, and asked:

"I have no problem with the number of atoms in the C12 cluster that was separated from the original mixed carbon cluster. After all, the quantity is large, and the mass weighing method can be used to weigh directly, which is the same as the verification of the centrifugal method.

However, how do you measure the number of 14 atoms in the isolated C14 clusters? You know, the number of C14 atoms is scarce, and a few less will cause the error rate to reach beyond the rated threshold. And, how does your new method ensure that there is no C14 in the separated C12 clusters? Will there still be sticking together and not separating?"

Gu joked, and he immediately took out some photos of the instrument recording the experimental process - of course, the so-called "photo" is actually just a colloquial term, because there are no traditional optical camera instruments and technologies that can accurately photograph things at the atomic level.

So, that thing is actually something like some kind of capturing raster records, and non-physics majors just need to know that this thing can record the experiment. How the atomic flow passes through the accelerator tube and deflector is on the line.

"This is recorded by the capture raster of the Faraday cylinder and the deflector. In our instrument, a terminal voltage of 1 million volts is added to completely strip the surface electrons of all the atoms in the carbon cluster, and according to the acceleration generated by the Lorentz force, the atom cluster is scattered. So the second question, after you read this part of the data, you should not have any doubts......"

Gu Yu said, and also instructed the Sakai layman to teach how to read the relevant records.

It took about ten minutes to explain this point clearly.

Then, he began to answer the first question of the other party, which was "how accurately does his instrument weigh the number of C14 atoms".

After all, C12 atoms can be weighed according to the algorithm of "1 mole (mole) carbon 12 atoms weigh 12 grams", because many and heavy, macroscopic weighing can be weighed.

(Note: 1 mole atom is 6.02×10 to the 23rd power.) One more nonsense, so that students who didn't study chemistry in high school read it kindly.

In addition, the "macro" in the previous sentence is a few milligrams or even a few micrograms. Because 1 microgram has 10 to the 15th power of carbon atoms, that is, hundreds of trillions, which is enough for isotope identification)

However, the C14 atom, which is at least a trillion times less than the C12 atom, is difficult to weigh. It is possible that the number of C14 atoms collected in an experiment is only a few trillions of a milligram.

In the traditional centrifugal method, the final weighing of the number of C14 atoms is not very accurate, and there is always an error equivalent to at least a few percent of the total number, which leads to an error of at least a few hundred years in dating.

"Therefore, my set of instruments does not use the mass weighing method used in centrifugal method to calculate the number of C14 atoms - centrifugal method uses centrifugal force to separate atoms, and I use Lorentz force to separate atoms. That being the case, without bothering the two masters, I ended up measuring the total charged charge of all the C14 ions.

When the charge is balanced, the electric potential difference formed by calculating the number of electrons in the suspended negative electrode can not be calculated? ”

"That's right...... Why didn't I think of ......," exclaimed Professor Sakai.

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Sogou