# Can you use a photon's torque to change a molecule?

Can you use the torque of a photon to change bond angles, etc.? 11-Cis-Retinal to the all trans version, in the eye, is a good illustration [1].

Note: This phenomenon can be observed by closing blinds, allowing the sun to shine through, you get light beams. If you blow a smoky material past it, you can observe this phenomenon of light.

### References

1. Rego, L.; Dorney, K. M.; Brooks, N. J.; Nguyen, Q. L.; Liao, C.-T.; Román, J. S.; Couch, D. E.; Liu, A.; Pisanty, E.; Lewenstein, M.; et al. Generation of Extreme-Ultraviolet Beams with Time-Varying Orbital Angular Momentum. Science 2019, 364 (6447), eaaw9486. https://doi.org/10/gf4f6h.
• Molecules are solid, they don't change. Except the rare cases when they do. Can you change a piece of metal with your bare hand? Normally no, but sometimes yes. Same thing here. – Ivan Neretin Jul 2 '19 at 5:49
• Probably not, normally the total energy of a photon is needed to produce an excited state, (by being absorbed by the molecule), and from which isomerisation/bond breaking can occur. This is the case in your example where 2 to 3 eV are needed, and the torque is not likely to be of sufficient energy. You should ask a question in Physics StackExchange to better understand what this torque actually is, as opposed to circular polarisation, for example. – porphyrin Jul 2 '19 at 7:17
• Hey Ivan, thanks for the information! – user80633 Jul 2 '19 at 7:23
• Porphyrin- I am not trying to get the photon to be absorbed by an electron. I am wondering if bombarding a specific bond with photons with torque could change the orientation of a bond. i only provided the study to give more information. Thank you! Just trying to figure things out. – user80633 Jul 2 '19 at 7:35
• @porphyrin At technique uses optical spin angular momentum (which is tied to the polarization), not the orbital angular momentum (tied to the spatial dependence) which is at play in the referenced publication, i.e. the two have very little to do with each other. They're similar, but they operate at vastly different length scales - OAM will only couple to objects at the size of the wavelength. – Emilio Pisanty Jul 2 '19 at 11:27