Discover how thermochromatography enables scientists to isolate and study superheavy elements that exist for mere seconds
Imagine trying to find a single, fleeting grain of sand in a moving dump truck—a grain that will vanish in less than a minute. This is the daily challenge for scientists hunting superheavy elements, the exotic, unstable atoms at the very edge of the periodic table. These elements don't exist in nature; they are created one atom at a time in powerful particle accelerators, and they often decay into oblivion in the blink of an eye.
To prove their discovery, researchers must separate, identify, and study these atoms with breathtaking speed and precision. So, how do they catch something that exists for mere seconds? The answer lies in a beautifully simple yet powerful technique known as thermochromatography—a molecular race down a temperature slide that separates the champions from the also-rans.
Element 113
Thermochromatography exploits subtle differences in volatility to separate elements that may differ by only a few atomic numbers but have dramatically different chemical behaviors.
At its heart, thermochromatography is a race where the track itself determines the winner. The name gives it away: Thermo (heat) + Chromatography (color writing, but meaning separation). It's a method to separate chemical compounds based on their volatility—how readily they turn from a solid into a gas.
The process can be understood as a microscopic volcano where elements travel along a temperature gradient, depositing at their characteristic condensation points.
The experiment begins at the "hot zone," where newly created radioactive atoms are produced. This area is heated to several hundred degrees Celsius, enough to vaporize the target elements.
Connected to the hot zone is a long tube or column with a carefully controlled temperature gradient—from very hot to very cold.
Gaseous atoms are pushed by a carrier gas down the column. As temperature drops, each element deposits at its specific condensation temperature.
Elements vaporize and begin their journey
Less volatile elements deposit hereModerately volatile elements separate
Medium volatility elementsHighly volatile elements finally deposit
Highly volatile elements like NihoniumTo see thermochromatography in action, let's look at one of its most spectacular successes: the confirmation of the synthesis of Nihonium (Nh), element 113.
Nihonium is a superheavy element with a half-life of just seconds. It was produced by fusing a zinc-70 beam with a bismuth-209 target. The trick was to separate a handful of Nihonium atoms from a blizzard of other, more common radioactive byproducts.
A step-by-step hunt involving synthesis in a particle accelerator, vaporization, transport via helium gas, separation in a quartz column, and detection using radiation sensors.
| Element | Group | Deposition Temperature Range | Volatility |
|---|---|---|---|
| Nihonium (Nh) | 13 | -90°C to -150°C | High |
| Thallium (Tl) | 13 | -20°C to -50°C | Medium |
| Lead (Pb) | 14 | +250°C to +450°C | Low |
| Step | Isotope | Half-life | Decay Mode |
|---|---|---|---|
| 1 | ²⁸³Nh | ~100 seconds | Alpha decay |
| 2 | ²⁷⁹Rg | ~0.15 seconds | Alpha decay |
| 3 | ²⁷⁵Mt | ~9.7 milliseconds | Alpha decay |
| Parameter | Detail |
|---|---|
| Target | Bismuth-209 (²⁰⁹Bi) |
| Beam | Zinc-70 (⁷⁰Zn) |
| Product | Nihonium-279 + 1 neutron (²⁸³Nh + n) |
| Reaction | ²⁰⁹Bi + ⁷⁰Zn → ²⁸³Nh + ¹n |
The decay events corresponding to the Nihonium decay chain were detected in the deeply cold region of the column, around -90°C to -150°C. This proved two critical things:
Building and running these experiments requires a suite of specialized tools and reagents. Here are the key components of the toolkit.
The "anvil." These are the heavy, purified elements that are bombarded to create superheavy nuclei.
The "hammer." A stream of accelerated ions used to fuse with the target atoms.
The "conveyor belt." Transports the volatile product atoms without reacting with them.
The "race track." Provides a defined surface for the temperature gradient and atomic deposition.
The "coolant." Creates and maintains the ultra-cold temperatures required at the end of the gradient.
The "finish line camera." Precisely locates and identifies the radioactive decay of the deposited atoms.
| Item | Function in the Experiment |
|---|---|
| Enriched Stable Isotope Targets (e.g., ²⁰⁹Bi) | The "anvil." These are the heavy, purified elements that are bombarded to create superheavy nuclei. |
| High-Energy Ion Beam (e.g., ⁷⁰Zn) | The "hammer." A stream of accelerated ions used to fuse with the target atoms. |
| Inert Carrier Gas (e.g., Helium) | The "conveyor belt." Transports the volatile product atoms without reacting with them. |
| Chemical Gradient Tube (e.g., Quartz with Gold coating) | The "race track." Provides a defined surface for the temperature gradient and atomic deposition. |
| Cryogenic System | The "coolant." Creates and maintains the ultra-cold temperatures required at the end of the gradient. |
| Position-Sensitive Radiation Detectors | The "finish line camera." Precisely locates and identifies the radioactive decay of the deposited atoms. |
Thermochromatography is far more than just a purification trick. It is a powerful window into the fundamental properties of matter. By observing where an unknown element lands on the temperature slide, scientists can directly probe its volatility, its tendency to form chemical bonds, and confirm its place in the periodic table.
This technique was crucial not only for discovering Nihonium but also for confirming the properties of other superheavy elements like Copernicium and Flerovium .
In the relentless pursuit to map the farthest reaches of the periodic table, thermochromatography stands as a testament to human ingenuity—transforming the abstract hunt for a few vanishing atoms into a tangible, measurable race to the finish line.