Measuring H/sub 2//sup +/ vibrational wavepackets with sub-femtosecond precision
Bibliographic record
Abstract
Summary form only given. A major effort is underway throughout the world to develop single attosecond optical pulses or trains of attosecond pulses based on the physics of high harmonic generation. During high harmonic generation, an electron is removed from the atom by a strong laser field. The electric field causes it to move a large distance from the atom, only to drive it back when the laser field reverses its direction. High-harmonics are produced during the electron-ion collision that can follow. The duration of the electron-ion collision, usually referred to as "re-collision", largely determines the duration of the attosecond photon pulse. The electron wave packet can also be used to probe the parent ion. Although only one electron can be involved, we adopt the language of electron beams to draw attention to the potential applications of re-collision electrons. We characterize the unusually large current density and the very brief duration seen by the ion with one-femtosecond precision. To do this, we ionize H/sub 2/ molecules, forming simultaneously two wave packets. One is a vibrational wave packet in H/sub 2//sup +/ and the other is the electron wave packet that we wish to study. By forming them together we can use the initial motion of the vibrational wave packet as a very fast clock (1/2-vibrational period /spl sim/ 7.5 fs) against which we measure the electron wave packet motion. We observe the re-collision, and measure the current density, by observing the kinetic energy of the protons released by the fragmentation of H/sub 2//sup +/ upon double ionization or collisional excitation. The kinetic energy resolution determines the time resolution of the "clock" to be /spl sim/ 1 fs.
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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) | 0.003 | 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".