The X+ 2Πg, A+ 2Πu, B+ 2Δu, and $\mathrm{a}^+\ ^4\Sigma _{\mathrm{u}}^-$a+Σu−4 electronic states of ${\rm Cl}_2^+$ Cl 2+ studied by high-resolution photoelectron spectroscopy

Abstract

Photoelectron spectroscopic study of the E ⊗ e Jahn-Teller effect in the presence of a tunable spin-orbit Partially rotationally resolved pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the three isotopomers ( 35 Cl 2 , 35 Cl 37 Cl, and 37 Cl 2 ) of Cl 2 have been recorded in the wavenumber ranges 92 500-96 500 cm −1 , corresponding to transitions to the low vibrational levels of the X + 2 g ( = 3/2, 1/2) ground state of Cl + 2 , and 106 750-115 500 cm −1 , where the a + 4 − u ← X 1 + g , A + 2 u ← X 1 + g , and B + 2 u ← X 1 + g band systems overlap with transitions to high vibrational levels (v + > 25) of the X + state. The observation of Franck-Condon-forbidden transitions to vibrational levels of the X + state of the cation with v + ≥ 25 is rationalized by a mechanism involving vertical excitation of predissociative Rydberg states of mixed singlet-triplet character with an A + ion core which are coupled to Rydberg states converging to high-v + levels of the X + state. The same mechanism is proposed to also be responsible for the observation of Cl + − Cl − ion pairs and quartet states in the photoionization of Cl 2 . The potential energy function of the X + state of Cl + 2 was determined in a direct fit to the experimental data. Transitions to vibrational levels of the A + 2 u, 3/2 and B + 2 u, 3/2 states of Cl + 2 could be identified using the results of a recent analysis of the strong perturbation between the A + 2 u, 3/2 and B + 2 u, 3/2 states of Cl + 2 observed in the A + − X + band system [Gharaibeh et al., J. Chem. Phys. 137, 194317 (2012)], and transitions to several vibrational levels of the upper spin-orbit component ( 2 u, 1/2 ) of the A + state were detected in the photoelectron spectrum of Cl + 2 . The a + 4 − u ← X 1 + g photoelectron band system, which is nominally forbidden by single-photon ionization from the ground state was also observed for the first time and its vibrational and spin-orbit structures were analyzed. The 4 − u state is split into two spin-orbit components with = 1/2 and = 3/2, separated by 37.5 cm −1 . The vibrational energy level structure of both components is regular, which indicates that the splitting results from the interaction with one or more distant ungerade = 1/2 or = 3/2 electronic states. © 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH3–CC–CH+3and CD3–CC–CD+3

“…The photoelectron spectra obtained by collecting the electrons produced by these three pulses had each a resolution of ∼0.3 cm −1 . After correction for the respective field-induced shifts of the ionisation thresholds, the three spectra were added, which enabled an improvement of the signal-to-noise ratio of the photoelectron spectra without reduction of the spectral resolution [31].…”

The adiabatic ionisation energy of CO2

“…This procedure enables one to combine the high resolution of the spectra obtained with individual pulses with the high sensitivity resulting from their summation. In a previous implementation of this method [16], a cold gas sample in a pulsed skimmed supersonic beam was used, with negligible Doppler broadening, resulting in different line widths for the spectra obtained from different pulses of the sequence. Consequently, only a subset of the spectra having similar linewidths could be added, resulting in a loss of signal-to-noise ratio.…”

“…In this research note, we report on a measurement of the adiabatic ionization energy of CO 2 with an uncertainty reduced by more than five times over previous results. The measurement exploits a multipulse electric-field ionization sequence to record PFI-ZEKE-PE spectra that enables the selective ionization of high Rydberg states lying within energy bandwidths of only 0.1 cm −1 [15,16], which is less than the Doppler width (full width at half maximum, FWHM) of 0.2 cm −1 of a roomtemperature CO 2 sample at a photon wave number of 111 000 cm −1 .…”

Continuity of heavy Rydberg behaviour in the ungerade ion-pair states of H 2

“…The long vibrational progressions observed in the ion-pair states of I 2 , Br 2 , Cl 2 IBr and ICl have all been found to exhibit Rydberg behaviour [3,4]. A short Rydberg series has also been observed in the vibrational levels of Cl 2 by Mollet and Merkt [5,6]. Ion-pair vibronic states in H 2 were first observed in a timedomain experiment and named Heavy Rydberg (HR) states by Reinhold and Ubachs [7].…”