Associative ionization of excited sodium species with various ligands: assessing relative bonding strengths of ion–ligand interactions

Electron Densities and Alkali Atoms in Exoplanet Atmospheres

“…Associative ionization of sodium atoms with water molecules, although important in the atmospheres of our solar system, is not significant for the high temperature exoplanet atmosphere as the bond energy is small (∼1eV) and the formed ligands would not survive in the atmosphere in significant abundances (Gilligan et al 2001). This effect is already demonstrated for the alkali dimers described above.…”

“…The reduction in the involved energy barriers for these reactions is not as large as for the ion-pair formation processes with other species, and thus these mechanisms are not efficient. In any case, the ion-pair recombination (reverse of the above processes) is a barrierless reaction, therefore the net contribution of the ion-pair mechanism will be important only at very high temperatures and does not affect our conclusions for HD 209458 b. Associative ionization of sodium atoms with water molecules, although important in the atmospheres of our solar system, is not significant for the high temperature exoplanet atmosphere as the bond energy is small (∼1eV) and the formed ligands would not survive in the atmosphere in significant abundances (Gilligan et al 2001). This effect is already demonstrated for the alkali dimers described above.…”

Cationic Noncovalent Interactions: Energetics and Periodic Trends

“…This factor does not affect the determination of the thresholds for TCID experiments, although Amicangelo and Armentrout included this factor in their analysis of competitive dissociations from bis-ligated LM + (C 6 H 6 ) complexes . This factor has not been routinely included in previous adjustments of free energy values to enthalpies. ,,, Table does include this factor in any values converted from free energies. A similar correction may be needed for other π-complexes (and other symmetric ligands) as discussed below.…”

“…118 For a wide range of ligands, TCID values and those from McMahon agree with each other and with several levels of theory, whereas the Castleman values are systematically higher (by 21 ± 10 kJ/mol compared to the TCID values). 118 One possible explanation for this disparity was explored later by Gilligan et al, 119 who noted that the means used to produce Na + in these studies also formed Na metastables, which could enhance the production of the Na + − ligand complexes by associative ionization.…”

An experimental and theoretical dissection of potassium cation/glycine interactionsElectronic supplementary information (ESI) available: Fig. S1 shows a complete set of figures for collision-induced dissociation of six potassiated complexes with Xe. Table S1 lists vibrational frequencies and average vibrational energies at 298 K of the neutral molecules and potassiated complexes determined from vibrational analysis at the MP2(full)/6-31G(d) level. Table S2 lists rotational constants for the potassiated com

“…Subsequent analysis by the Castleman group revealed that the thermionic ion source used in these studies also produces neutral alkali metastables that then react with the ligand of interest in an associative ionization process to form M þ (L) complexes. 65 This yields an increased intensity of the M þ (L) complex compared to the bare M þ ion, such that the equilibrium measurement of the M þ (L) binding energy overestimates the true bond energy. In the HPMS studies of Kebarle and co-workers, 21,22,64 a thermionic ion source was used to generate potassium ions, such that the associative ionization process might be contributing to the K þ (L) signals leading to the larger bond energies measured.…”