Li Dong didn’t quite register what Professor Zhang Lufang had just said.
Huh?
’Academicians are working on this?’
’A little idea that just popped into my head...’
’How did it turn into a problem that academicians are wrestling with?’
’Am I playing in the big leagues or what?’
"Teacher Zhang, you said... how many academicians?"
The elderly Professor Zhang Lufang leisurely took a sip of water and spoke.
"Yes, several."
"And now, there are only a few academicians still working on it."
"This field was really hot over a decade ago."
"Both at home and abroad, a ton of research groups threw money, people, and equipment at it."
"And what’s the result today?"
"Many groups have pulled out and moved on to other fields."
"Only a few academicians are left, still gnawing away at this problem."
Li Dong’s mouth hung open as a thought surfaced in his mind.
’Is it really that hard?’
As if worried he didn’t grasp the difficulty and significance of the topic, the professor didn’t beat around the bush.
"You know about X-ray absorption edges, right?"
"I do." Li Dong nodded quickly.
"Moseley’s Law, right? The characteristic absorption edge is the element’s fingerprint."
"Exactly."
"It’s been 130 years since Roentgen discovered X-rays in 1895."
"In these 130 years, hospitals have used them, materials science institutes have used them, and even archaeologists have used them."
"But there’s one line that no one has managed to cross in over a century."
"What line?"
Li Dong pressed.
Zhang Lufang held up one finger.
"Ten thousand."
"Huh?"
"To detect an element’s absorption edge, to make it visible to a detector, you need at least ten thousand atoms in the sample."
"Any fewer, and the signal gets drowned out by the noise."
"This is the recognized sensitivity limit for X-ray absorption spectroscopy. No one has been able to budge it for over a hundred years."
The summer camp paper Qi Yu had talked about at dinner that day flashed through Li Dong’s mind—"using an element’s characteristic absorption edge as an atom’s fingerprint."
Qi Yu herself had admitted that her method could only achieve sub-micrometer resolution at best.
It was a world away from the single-atom level.
"You know about STM, right?" the professor asked again.
"Yes, Scanning Tunneling Microscope. It can resolve individual atoms."
"Correct."
"STM can see individual atoms clearly, but it has one fatal flaw."
"It can see atoms, but it can’t identify them."
"If you put an iron atom and a cobalt atom next to each other and ask an STM to tell them apart, it can’t."
"It sees the bumps in the local density of states, not the element itself. Am I right?"
Li Dong nodded.
"So for the past few decades, a whole bunch of people have been thinking about the same thing."
"Is it possible to weld the elemental fingerprinting of X-rays and the single-atom spatial resolution of an STM onto a single tip?"
Li Dong’s breath caught in his throat.
’Isn’t that the exact same line of thought I just had?’
"What’s the hard part?" he asked.
Seeing that she had piqued Li Dong’s interest, Professor Zhang Lufang slowly held up three fingers.
"First, there’s the signal problem."
"The excitation signal from a single atom is several orders of magnitude lower than the background noise. A conventional detector can’t even hear it."
"Then there’s the issue with the tip."
"You have to fabricate a tip with a core that can conduct tunneling current, an insulating outer layer, and an outermost layer that’s grounded to shield from stray light. As for that, you can count the number of labs in the world that can make one on a single hand."
"But the hardest part is actually the beamline."
"Synchrotron radiation sources are already scarce. A beamline that can be dedicated to soft X-rays and also allows you to connect an STM is even rarer."
"Right now, the only one in the entire world that barely qualifies is the XTIP beamline at Argonne National Laboratory."
She paused, giving Li Dong a meaningful look.
"So, that little inspiration of yours sounds quite brilliant."
"But if you were to actually pursue it, you could count the number of domestic research groups capable of even entering the field on one hand."
"The heads of these groups are all academicians."
"And they’re stuck themselves. They’ve been stuck for years, unable to produce a clean spectrum."
Li Dong’s mouth twitched.
’I’ve already cursed Madam Curie and Mendeleev a hundred times over.’
’I was just trying to get you two to bicker a little, did it have to cause such a huge commotion?’
The elderly Professor Zhang Lufang watched his expression with a gentle smile.
"The topic is difficult, but if it’s you, you could give it a try."
"You’ve done an excellent job with your math, haven’t you?"
Li Dong felt like the old professor was mocking him.
’This kind of problem in chemistry, especially this direction of welding X-ray elemental fingerprinting with STM single-atom resolution, isn’t like math, where a good brain is all you need.’
’It requires fighting tooth and nail for beamline time at a synchrotron facility, a cleanroom with a micro/nanofabrication platform for making special tips, an ultra-high vacuum system for preparing single-atom samples, an ultra-low-noise detector capable of capturing single-atom signals, and a whole team of research workhorses willing to pull all-nighters to calibrate the equipment.’
’I really can’t handle all that right now.’
’Besides...’
’Why should I have to handle it?!’
’He’d come to study chemistry to relax in the first place.’
’Not to get involved in some insane research project.’
’And not for the red envelopes in the group chat, either.’
’Really.’
’But even relaxing requires a path, right?’
’You can’t just relax aimlessly.’
’It has to be planned relaxation, purposeful relaxation, targeted relaxation.’
So, Li Dong mulled it over and cleared his throat.
"Teacher Zhang, then... how should I relax—oh, no, I mean, study—from here on out?"
Zhang Lufang gave him a strange look.
’Did this kid just say "relax"?’
The corner of her mouth twitched, but she didn’t call him out on it.
A Yan University undergraduate coming over to the School of Chemistry to "relax"... He was really one of a kind.
Nevertheless, the professor still thought about it very seriously for a moment.
This was, in fact, the role of a teacher to a genius...
Not to teach him how to learn, but to show him which path to take.
She put down her thermos and said.
"Alright, I’ll lay out a path for you."
"You should probably get a notebook and write this down, shouldn’t you?"
The doors to Li Dong’s Memory Palace had already swung open, but upon hearing the professor’s words, he immediately pulled a notebook and pen from his bag and pretended to open it.
Zhang Lufang smiled when she saw this.
"First, go and thoroughly digest You Xiaoceng’s *Coordination Chemistry*. Pay special attention to the Chapters on Crystal Field, Ligand Field, and the Molecular Orbital Method, the parts that discuss d-orbital splitting. You need to work through the formulas one by one."
Li Dong feigned scribbling a few strokes in his notebook, while in his mind, the Memory Palace had already pulled out the book on Coordination Chemistry.
The professor took a sip of tea and continued.
"Next is group theory. You have a strong foundation in math, so this part won’t be difficult for you. But don’t just treat it like a math problem, alright?"
"You also need to understand that whether a molecule absorbs light is, at its root, determined by symmetry selection rules."
"The Laporte rule, spin selection rules... don’t just memorize them. You need to be able to derive them from group theory."
Li Dong suddenly realized that the professor’s last two points were actually about the same thing: what fundamentally allows an electron to transition between orbitals.
"Once you’ve sorted all that out, go tackle the X-ray Chapters in *Spectroscopy and Photochemistry Fundamentals*."
"Don’t be put off by the old-fashioned title. The core concepts—X-ray absorption and emission, fine structure—it’s all in there."
"Especially Moseley’s Law. Don’t think of it as some boring, century-old relic. The root of that little inspiration you had today still lies with him."
Li Dong thought to himself, ’How could I possibly look down on him? The great Moseley has been in my group chat this whole time, he just never says anything...’
The professor had no time to worry about what Li Dong was thinking. She continued.
"There are two more books you should tackle together: *Surface Physical Chemistry* and *Introduction to Scanning Probe Microscopy*."
"The first one will help you understand how atoms adsorb onto metal surfaces and how ligands anchor them. The second will explain what that tunneling current under the tip actually is."
"You probably haven’t touched on these two areas, so just force your way through them. If you get stuck, come find me anytime."
"Once you’ve laid this entire foundation, then you can go through the literature from the top international groups on single-atom characterization from the last decade."
"By then, you’ll have a crystal clear idea of where to take that inspiration of yours."
After speaking, the professor waved her hand dismissively.
"Alright, go and study on your own for now. You always have to drill into the knowledge yourself first, don’t you?"
Li Dong nodded repeatedly.
"Yes, yes, of course."
He closed his notebook, but in truth, he was already antsy to get started.
After the professor’s lengthy explanation, the scattered pieces of knowledge about Coordination Chemistry, X-rays, and synchrotron radiation in his Memory Palace began to slowly align.
Faint, thin lines were starting to connect between some of the nodes.
Of course, there were still vast blank spaces.
Those blank spaces were precisely what the professor had just told him to go learn.
Sigh.
’This old professor is really something else.’
Li Dong stood up and gave the professor a proper, formal bow.
"Teacher Zhang, thank you. I’ll be going now."
Zhang Lufang waved her hand with a cheerful smile.
"Go on, go on."
As Li Dong pulled the door open, he nearly collided with someone outside.
The other person was also startled.
Li Dong looked up.
It was Qi Yu.
Qi Yu was also taken aback to see Li Dong.
Then, Li Dong said reflexively.
"Hi, senior!"
"Bye, senior!"
And with that, he vanished.
Qi Yu: ???
’What’s with this guy? Why does he run the second he sees me?’
’Did I get fat recently?’
Qi Yu subconsciously touched her face.
Then, her head full of questions, she pushed the door open and entered Zhang Lufang’s office.
"Teacher."
Zhang Lufang looked up, smiling.
"Ah, Xiaoyu."
As Qi Yu poured herself a glass of water, she asked casually.
"Teacher, what was Li Dong here for just now?"
Zhang Lufang glanced at her disciple.
"He came to ask me a few questions."
Qi Yu’s hand paused mid-pour.
’Ask questions?’
’This junior of mine...’
’Is he tired of playing around with math?’
’Has he started playing around with chemistry now?’

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