Chemiluminescent reactions of second-row atomic ions. I. Al++H2→AlH+(A 2Π, B 2Σ+)+H

Abstract

Light emission from the impact of Al+(1S,3P) ions on H2 molecules at 5.2 to 13.8 eVCM was spectrally analyzed. It was found to consist of two band systems. Of the known A 2Π–X 2Σ+ transition, numerous new bands were observed, allowing a first experimental determination of vibrational constants. In addition, a predicted B 2Σ+–X 2Σ+ system was observed for the first time. Relative emission cross sections for the two systems and for the 1S and 3P reactant species were measured. They parallel closely the trends in the isovalent system B++H2. One important difference is, however, the existence of a large (∼3.5 eV) activation barrier in the dominant Al++H2 reaction channel. This is explained in terms of adiabatic potential hypersurfaces.

Rotational state analysis of AlH+ by two-photon dissociation

“…Here we study one such molecular ion, AlH + . Owing largely to astrophysical interest, some spectroscopic properties of the AlH + molecular ion are already well understood with good agreement between experiment [11,12,13,14] and theory [15,9]. Here, we extend our previous calculations [9] to include states relevant for an experimentally convenient pathway for REMPD rotational state readout, and we predict an experimentally accessible dissociation cross-section.…”

Optimizing Quantum Control Pulses with Gaussian Process Priors: The Spectral Way

“…Figure displays the potential energy surfaces (PESs) of the electronic states X 2 Σ + , A 2 Π, B 2 Σ + , and A 4 Π of the AlH + molecule as well as the remaining Hamiltonian terms. − In this study, we have restricted our analysis to the scenario where AlH + ions are oriented in the same direction. Consequently, our investigation primarily concentrates on the anisotropic behavior of the system .…”

Challenges of laser-cooling molecular ions

“…The A 2 Π-X 2 Σ + system of both BH + and AlH + are well studied in emission from hollow cathode discharges [47,48,30], and chemiluminescent ion-molecule reactions [49,35] have yielded detailed rotational constants for the first two vibrational levels of the X 2 Σ + ground state along with low-resolution spectra of a few diagonal vibrational bands. For the BH + cation, 15 rovibrational energy levels of the ground state (v=0-4 and N=0-2) have been assigned by the extrapolation of photo-selected high Rydberg series of neutral BH [32].…”

“…On the basis of spectroscopic data available in the literature (see the appendix), our molecular ion survey found BH + [28,29,30,31,32,33] and AlH + [34,29,35,36,37] to be among the most promising candidates. In this manuscript, we review all identified challenges of maintaining a closed excitation scheme for direct laser cooling of BH + and AlH + stored in ion traps.…”