Photostop: production of zero-velocity molecules by photodissociation in a molecular beam

Abstract

Photostop is an accessible technique capable of producing atoms or molecules at a standstill in the laboratory frame. Starting with a NO₂/Xe molecular beam with a mean velocity of 415 m s⁻¹ and a longitudinal translational temperature of 6 K, NO₂ molecules are photodissociated to yield NO(X ) fragments with a recoil speed equal to the molecular beam speed. The fraction of NO fragments that recoil opposite to the molecular beam are produced with a 6 K longitudinal velocity distribution centred at zero. The NO molecules are allowed to ‘evaporate’ from the probe volume by waiting for 10 µs and the molecules left behind are probed with a translational temperature of 1.6 K along the molecular beam axis and an estimated density of 10⁷ cm⁻³ per quantum state. Through the choice of suitable precursors, the photostop technique has the potential to extend the list of atoms and molecules that can be slowed or trapped. It should be possible to accumulate density in a trap through consecutive loading of multiple pulses.

†Current address: AECL Chalk River Laboratories, Deep River ON, K0J 1J0, Canada.

Keywords:

• cold molecules
• deceleration
• trapping
• photodissociation

Acknowledgements

We would like to thank the EPSRC for funding (GR/S22783/01 and EP/D055237/1). We also thank Miss Laura Harris, Mr Rob Rae and Mr Oliver Willis for their help. We also acknowledge Prof. Tim Softley for useful discussions and Prof. Jeremy Hutson for his scrutiny of the manuscript.

Notes

†Current address: AECL Chalk River Laboratories, Deep River ON, K0J 1J0, Canada.