Excited Electronic State Cross Sections for Group 3 Halide and Oxide Production: Evaluating Relative Excited-State Quantum Yields

Chalek, Carl L.; Gole, James L.; Dixon, David A.

doi:10.1021/acs.jpca.2c01780

Cited by 1 publication

(5 citation statements)

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“…Both oven and reaction chambers can be independently monitored. Additional features for quantum yield determinations have been added and are discussed in more detail in the following paper …”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

“…Accordingly, ΔH vap for forming a vapor composed solely of ground-state atoms would be somewhat less (∼3 kcal/mol) and ΔH vap for forming 2 F atoms is considerably higher (16 kcal/mol). Inequality (16) holds for ground-state atoms but not for 2 F atoms. Therefore, the observed chemiluminescence is due to reaction of groundstate 2 D La atoms.…”

Section: ■ Introductionmentioning

confidence: 94%

“…Additional features for quantum yield determinations have been added and are discussed in more detail in the following paper. 16 For the reactions of the three metals studied, the following crucibles were used: tungsten crucible for La and Y and Sc 2 O 3 + thorium in a baffled tantalum crucible or the pure metal in a tungsten crucible for the temperature-dependent studies for Sc. The metal being vaporized effuses from an orifice which ranges in size up to 1/8″ diameter, 1/2″ from the top of a capped crucible.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The observations in both the scandium−chlorine and scandium−bromine systems highlight the propensity of the group 3 + halogen reactions to target product formation in the 340−370 nm region selectively as long as this region is energetically accessible. 16 The potential energy curves for ScCl in the Supporting Information show that there are three excited singlet 1 Π 1 and 1 Σ 0 + states with significant transition dipole moments in the spectral region of interest from 354 to 359 nm with electron occupancies with two electrons in the 3d and 4p orbitals or two electrons in the 3d orbitals.…”

Section: ■ Introductionmentioning

confidence: 99%

“…A linear least squares analysis of the data points for intensity versus reciprocal temperature 173 yields a value of 97.5 kcal/mol for −R d(ln I)/ d(1/T B ) for La + F 2 . This value should not be substituted into eq 12 or inequality (16) because the observed value must be multiplied by a correction factor which accounts for the change in the relative population with temperature for the La atomic state under consideration. For the 2 D state, the correction factor will increase the effective value of −R d(ln I)/d(1/T B ), whereas the effective value will be lowered for the 2 F state.…”

Section: ■ Introductionmentioning

confidence: 99%

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Observation of Selectively Populated Monohalide Excited States from the Reactions of Group 3 Metal (Sc, Y, and La) Monomers and Dimers with Halogen-Containing Molecules

et al. 2022

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The chemiluminescent reactions of the group 3 metals Sc and Y with F 2 , Cl 2 , Br 2 , ClF, ICl (Sc), IBr (Y), and SF 6 and La with F 2 , SF 6 , Cl 2 , and ClF have been studied at low pressures (6 × 10 −6 to 4 × 10 −4 Torr) using a beam-gas arrangement and extended to the 10 −3 Torr multiple collision pressure range. Contrary to previous reports, the observed chemiluminescent spectra are primarily attributed to emission from the metal monohalides. Extensive pressure and temperature dependence studies and high-level correlated molecular orbital theory calculations of the bond dissociation energies support this conclusion and the attribution of the chemiluminescence. Evidence for the "selective" production of a monohalide excited electronic state is obtained for several of the Sc and Y reactions. All reactions producing the metal monofluorides are first order with respect to the oxidant, while reactions producing the monochlorides and monobromides are found to be "faster than first order" with respect to the oxidant. This difference is associated with the metal halide bond dissociation energies and the metal halide product internal density of states. Analysis of the temperature dependence for six representative reactions indicates that the "selective" excited-state formation of the metal monohalides proceeds via a direct mechanism with negligible activation energy. We compare and contrast the present results with previous experiments and interpretations which have assigned the selective emission from these systems to the group 3 dihalides produced in a two-step reaction sequence analogous to an electron jump process. The current results suggest a distinctly different interpretation of the observed processes in these systems. The observed selectivity observed in these studies is remarkable given the significant number of known and potential excited states in the scandium and yttrium halides as well as their different electronic configurations.

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Section: Experimental and Computational Methodsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 94%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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