TIME to chuck out another well-known scientific 鈥渇act鈥� 鈥� that to persuade positively charged atomic nuclei to bind together into molecules you need negatively charged electrons to balance out their repulsion.
Researchers have now figured out a way to keep the nuclei together with nothing more than a couple of tabletop lasers, and not an electron in sight. They hope that they will eventually be able to force nuclei to collide, allowing physicists to watch nuclear reactions without a billion-dollar particle accelerator.
Lasers have been used to nudge electrons that would normally pop off atoms back towards their nuclei 鈥� for example, to stabilise hydrogen atoms loaded with three times the normal number of electrons. But up to now no one considered using lasers to glue particles with like charges together, says Misha Ivanov of the National Research Council Canada in Ottowa.
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His team now proposes doing just that. The idea is to use a pair of lasers to kick the positively charged nuclei into stable loops around each other, thwarting their mutual repulsion. 鈥淚t鈥檚 a very easy picture to imagine, although it鈥檚 a little bit brutal,鈥� says Ivanov. 鈥淪uppose you are being attacked by a dog. You are trying to kick the dog away. But when you kick the dog away, it runs around in a circle to the other side to bite you there. You kick him on that side, and then he runs back. As a result, he stays in the circle.鈥�
The team鈥檚 computer simulations show that lasers which constantly rotate their polarity could provide enough kicks in the right direction to force one nucleus to constantly circle another in an electron-less 鈥渕olecule鈥� (see Graphic). Laser pulses with an intensity of roughly 1019 (10 billion billion) watts per square centimetre 鈥� which is feasible with today鈥檚 tabletop systems 鈥� would be enough to do the job. The molecules would be stable for around 250 femtoseconds (1/4000th of a nanosecond). That鈥檚 not enough to take part in any chemical reactions, but still a relatively long time on a molecular scale.
Most physicists would find such a feat impressive in itself. But the real goal requires lasers packing about 100 to 1000 times as much power. Researchers at the Advanced Laser Light Source in Montreal, Canada, hope to achieve this within five years. This would slam the nuclei close enough together to trigger a nuclear reaction. More difficult will be making the laser pulses ramp up to full intensity twice as fast as they do now, to catch and hold the nuclei in place before their repulsion rips them apart.
It鈥檚 going to be hard, says Ivanov, 鈥渂ut not impossible鈥�.
Ivanov鈥檚 tabletop laser technique might one day allow physicists to study nuclear collisions far more cheaply than with particle accelerators. In case that doesn鈥檛 work as well as hoped, the team is working on using lasers to kick electrons into smash-ups with their parent nuclei, so they can watch those collisions too.