An experimental setup to study delayed electron emission upon photoexcitation of trapped polyatomic anions

A Velocity Map Imaging (VMI) spectrometer has been designed and integrated with an electrostatic ion beam trap to study delayed electron emission from trapped polyatomic anions upon photodetachment. The VMI spectrometer is small in size and can record a wide range of photoelectron energies, with variable magnification. Delayed electron emission can be recorded in our experimental setup for any time duration after the photoexcitation of the polyatomic anions. Experiments were carried out with trapped O− and C5− ions to demonstrate the capability of the spectrometer. Delayed electron emissions from C5− as well as prompt photoelectrons from O− were detected by the VMI spectrometer upon photoexcitation. The design and performance of the spectrometer are presented in detail.