Discussion Overview
The discussion revolves around the transition of neon from its ground state to excited states, particularly focusing on the excitation energies observed in the Franck-Hertz experiment. Participants explore the reasons behind the specific energy levels at which current decreases, questioning why transitions occur at 19 eV rather than 17 eV, and the implications of angular momentum conservation during these transitions.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants note that the lowest excited energy state of neon is at 1(s^2)2(s^2)2(p^5)3(s^1) with an excitation energy of about 16.9 eV, and the next state at 1(s^2)2(s^2)2(p^5)3(p^1) with about 19 eV.
- There is a question regarding why the Franck-Hertz experiment shows current decreases at 19 eV and not at 17 eV, leading to speculation about the nature of the transitions involved.
- One participant suggests that the angular momentum conservation during collisions might explain the preference for the 19 eV transition, where the orbital angular momentum does not change (Δl=0) and the total angular momentum remains constant (ΔJ=0).
- Another participant points out that there is also a transition corresponding to 16.85 eV that involves a change in angular momentum (Δl=-1), which may be less likely to occur.
- Concerns are raised about whether Δl=0 contradicts selection rules, with one participant clarifying that these are collisional excitations and not governed by the same selection rules as electromagnetic absorption.
Areas of Agreement / Disagreement
Participants express uncertainty regarding the explanations for the observed excitation energies and the implications of angular momentum conservation. There is no consensus on the correctness of the proposed explanations or the relevance of selection rules in this context.
Contextual Notes
Participants acknowledge that the angular momentum coupling in the excited states of rare gases may not follow simple L-S coupling rules, indicating potential limitations in their reasoning.