Pulsed-field ionization spectroscopy of high Rydberg states (n=50–200) of bis(η6-benzene)chromium

Abstract

The ionization behavior of the high Rydberg states of bis(eta(6)-benzene)chromium in the presence of ac and/or dc fields has been explored. The application of an ac scrambling field at the time of laser excitation lengthens the lifetime of the Rydberg state by almost two orders of magnitude. The lifetime enhancement by the scrambling field is much more effective for n<100 than it is for n>100 Rydberg states. The pulsed-field ionization of Rydberg states of n<100 shows the typical diabatic ionization behavior for low n. The two distinct ionization behaviors observed for the relatively low (n=50-100) and high (n=100-200) Rydberg states suggest that the former originate from the optically accessed nf Rydberg series, whereas the latter are due to np Rydberg series. Based on the understanding of the ionization behavior of bis(eta(6)-benzene)chromium, the accurate ionization potential is deduced to give IP=5.4665+/-0.0003 eV. Optimization of the various electric field conditions greatly enhances the spectral sensitivity of the mass-analyzed threshold ionization (MATI) spectroscopy. The high-resolution MATI spectrum of the title molecule obtained here provides precise cationic vibrational frequencies for many skeletal and benzene ring modes. A number of vibrational modes are newly identified, and the ambiguity regarding to some mode assignments is now clearly resolved through the Frank-Condon analysis based on ab initio calculations.

Threshold Ionization of Cobaltocene: The Metallocene Molecule Revealing Zero Kinetic Energy States

“…The totally symmetric metal–ligand stretching and CH bending modes are also revealed by the MATI and ZEKE spectra of the [(η 6 ‐C 6 H 6 ) 2 M] (M=Ti, V, Cr, Mo) complexes 5d–f. In contrast to threshold ionization of the bis(benzene) derivatives studied, which involves a nonbonding ${{\rm{d}}_{z^2 } }$ metal electron (M=Cr, Mo)5d or an electron from the bonding molecular orbital (MO) formed mainly by the metal d xy and ${{\rm{d}}_{x^2 - y^2 } }$ wavefunctions (M=Ti, V),5f the MATI spectrum of cobaltocene corresponds to ionization of the antibonding single‐occupied MO derived from the metal 3d xz and 3d yz levels. Detachment of an electron from this MO strengthens the CoCp bond and decreases the Co–C average distance in the DFT‐optimized geometry from 2.120 Å for neutral [Cp 2 Co] to 2.061 Å for the [Cp 2 Co] + ion.…”

“…The precise adiabatic and vertical IEs of cobaltocene can now be easily determined. The electron detachment from a sandwich molecule in the absence of an electric field is observed at the wavenumber corresponding to the edge of the blue wing of the MATI peak 5f. The IEs found from the parameters of the lowest‐energy and the strongest MATI signal are, respectively, I ad.…”

Conical intersection seam and bound resonances embedded in continuum observed in the photodissociation of thioanisole-d3

“…Since the cationic ground state is bound and well-defined, assignments to cationic ground vibrational modes are straightforward when comparing with ab initio calculation results. MATI spectra reflect nuclear displacements associated with the particular S 1 vibronic state used as an intermediate state in the stepwise (1+1 ) ionization process according to the Franck-Condon principle, 27,28 and thus assignments of cationic bands provide the nature of the corresponding S 1 vibrational bands. In the MATI spectrum in which the S 1 -S 0 origin band was taken as an intermediate state, the D 0 -S 1 origin band is most strongly observed.…”

“…The experimental details for the MATI spectroscopy have been described previously. 27,28 Briefly, the parent molecule was excited to long-lived Rydberg states using the two-color two-photon excitation scheme before being ionized by the pulsed-field ionization technique using the electric pulse of ∼160 V/cm with a delay time of ∼50 μs after the laser excitation. The MATI ions were accelerated, drifted along the time-of-flight tube, and detected by dual micro-channel plates.…”

Rotationally resolved spectroscopy of the à A21←X̃ B21 transition of H2S+ above the barrier to linearity using the mass-analyzed threshold ionization photofragment excitation technique

“…In this work, the H 2 S sample was supersonically cooled and the vacuum-ultraviolet ͑VUV͒ laser pulse with the bandwidth of ϳ1 cm −1 was used for the ionization. In the ionization process, we have employed the direct ionization or mass-analyzed threshold ionization ͑MATI͒ technique 22,23 in order to rotationally cool down or select just a few rotational levels of the ground state H 2 S + ͑X 2 B 1 ͒, respectively. The subsequent photoexcitation corresponding to the à 2 A 1 ← X 2 B 1 transition of H 2 S + induces the dissociation into H 2 +S + products.…”