High Rydberg states of DABCO: Spectroscopy, ionization potential, and comparison with mass analyzed threshold ionization

Abstract

Doubly-resonant excitation/vibrational autoionization is used to accurately determine the ionization potential ͑IP͒ of the highly symmetric caged amine 1,4 diazabicyclo͓2,2,2͔octane ͑DABCO͒. The IP of DABCO excited with one quantum of the 24 (eЈ) vibration lies at ͑59 048.62Ϯ0.03͒ cm Ϫ1 , based on fitting 56 components of the np xy Rydberg series ͑␦ϭ0.406Ϯ0.002͒ to the Rydberg formula. Rydberg state transition energies and linewidths are determined using standard calibration and linefitting techniques. The IP determined from Rydberg state extrapolation is compared with that determined by mass analyzed threshold ionization ͑MATI͒. Effects of static electric fields on MATI signals measured for the high Rydberg states are discussed.

Resonant two-photon mass-analyzed threshold ionization spectroscopy of 1-fluoronaphthalene and 2-fluoronaphthalene

“…The strongest 0 + band appears at the ionization threshold. Since these ions are formed at an energy slightly below the ionization threshold, the determination of the adiabatic IE should consider the high-energy side of the 0 + band of the MATI spectrum [35]. In addition, because a spoiling field (À1 V/cm) is applied as mentioned previously, the measured value is slightly lower than the true IE due to the Stark effect [36].…”

Mass analyzed threshold ionization spectroscopy of o-fluorophenol and o-methoxyphenol cations and influence of the nature and relative location of substituents

“…The lowest energy bands (labeled 0 + ) in the MATI spectra correspond to the signal of the vibrationless cations. Because the threshold ions are formed by the pulsed field ionization of high n Rydberg neutrals with energy of a few wavenumbers below the true ionization threshold, the determination of the adiabatic IE should consider the high-energy side of the 0 + band [15]. In addition, the energy lowering (cm À1 ) due to the Stark effect [16] may be estimated by 4.0F 1/2 when a pulsed field F (in V/cm) is applied.…”

Adiabatic and vertical ionization energies of 1,4-diazabicyclo[2,2,2]-octane measured by zero electron kinetic energy spectroscopy and Rydberg extrapolation

“…DABCO has been the subject of numerous spectroscopic investigations using a number of high resolution techniques ͑laser-induced flourescence ͑LIF͒, 11,12 one-and two-color multiphoton ionization, [13][14][15][16]17,18 and mass analyzed threshold ionization ͑MATI͒ 16 spectroscopies͒ to study the first singlet excited state of the neutral, the high-n Rydberg states, and the ground electronic state of the ion. Adiabatic ionization energies have previously been reported by: photoelectron spectroscopy ͑7.23 eV; 58 313 cm Ϫ1 ͒; 19 two-color delayed ionization ͑7.19 eV; 58017 cm Ϫ1 ͒; 20 Rydberg series extrapolation ͑7.197 eV; 58 049.1Ϯ0.9 cm Ϫ1 ͒; 21 photoionization efficiency (58052Ϯ0.9 cm Ϫ1 ), 22 and possibly most accurately ͑although interestingly not with the greatest preci-sion͒ by Fujii et al 14 from their two-color multiphoton ionization spectrum ͑7.195 eV; 58032Ϯ5 cm Ϫ1 ͒.…”