1. Dopant ionization and efficiency of ion and electron ejection from helium nanodroplets.
- Author
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Asmussen, Jakob D., Ben Ltaief, Ltaief, Sishodia, Keshav, Abid, Abdul R., Bastian, Björn, Krishnan, Sivarama, Pedersen, Henrik B., and Mudrich, Marcel
- Subjects
DOPING agents (Chemistry) ,PHOTOIONIZATION ,ELECTRONS ,MASS spectrometry ,IONS ,HELIUM ,RESONANT ultrasound spectroscopy - Abstract
Photoionization spectroscopy and mass spectrometry of doped helium (He) nanodroplets rely on the ability to efficiently detect ions and/or electrons. Using a commercial quadrupole mass spectrometer and a photoelectron–photoion coincidence spectrometer, we systematically measure yields of ions and electrons created in pure and doped He nanodroplets in a wide size range and in two ionization regimes—direct ionization and secondary ionization after resonant photoexcitation of the droplets. For two different types of dopants (oxygen molecules, O
2 , and lithium atoms, Li), we infer the optimal droplet size to maximize the yield of ejected ions. When dopants are ionized by charge-transfer to photoionized He nanodroplets, the highest yield of O2 and Li ions is detected for a mean size of ∼ 5 × 1 0 4 He atoms per nanodroplet. When dopants are Penning ionized via photoexcitation of the He droplets, the highest yield of O2 and Li ions is detected for ∼ 1 0 3 and ∼ 1 0 5 He atoms per droplet, respectively. At optimum droplet sizes, the detection efficiency of dopant ions in proportion to the number of primary photoabsorption events is up to 20% for charge-transfer ionization of O2 and 2% for Li, whereas for Penning ionization it is 1% for O2 and 4% for Li. Our results are instrumental in determining optimal conditions for mass spectrometric studies and photoionization spectroscopy of molecules and complexes isolated in He nanodroplets. [ABSTRACT FROM AUTHOR] more...- Published
- 2023
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