Gas-Phase Reactions of Atomic Lanthanide Cations with Ammonia: Room-Temperature Kinetics and Periodicity in Reactivity
Bibliographic record
Abstract
Reactions of (14) atomic lanthanide cations (excluding Pm(+)) with ammonia have been surveyed in the gas phase by using an inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer to measure rate coefficients and product distributions in He at 0.35 +/- 0.01 Torr and 295 +/- 2 K. Primary reaction channels were observed corresponding to H(2) elimination with formation of the protonated lanthanum nitride and NH(3) addition. H(2) elimination was seen only in the reactions with La(+), Ce(+), Gd(+), and Tb(+) and occurs with these ions exclusively. NH(3) addition was seen with Pr(+), Nd(+), Sm(+), Eu(+), Dy(+), Ho(+), Er(+), Tm(+), Yb(+), and Lu(+). Higher-order sequential addition of up to five NH(3) molecules was observed with the Ln(+)(NH(3)) and LnNH(+) ions. The reaction efficiency of the primary reactions is seen to decrease as the energy required to promote an electron to make two non-f electrons available for bonding increases. The periodic trend in reaction efficiency along the lanthanide series matches quite closely the periodic trend in the electron-promotion energy required to achieve a d(1)s(1) or d(2) excited electronic configuration in the lanthanide cation. With La(+), Ce(+), Gd(+), and Tb(+), the electrostatic attraction between the atomic lanthanide cation and ammonia is sufficiently strong to provide enough energy to achieve electron promotion and to overcome any barriers to subsequent N-H bond insertion and H(2) loss, but this is not the case with the other lanthanide cations with which collisional stabilization of the intermediate adduct ion, with or without insertion of Ln(+), predominates.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".