Comment on “Brilliant Source of 19.2-Attosecond Soft X-ray Pulses below the Atomic Unit of Time”

Ardana-Lamas et al. recently reported a reanalysis of an attosecond streaking dataset originally published in Physical Review X 7 , 041030 (2017), claiming a pulse duration of 19.2 attoseconds (as). This claim represents the third substantially different pulse-duration estimate extracted from the same experimental data: approximately 332 as (upper limit) in the original publication, 165 as in a later reanalysis, and now 19.2 as—reported nearly 8 years after the experiment was published. The title of the work of Ardana-Lamas et al., first appearing in the preprint posted on 2025 October 5, is notably similar to that of the preprint, “Bright 25-attosecond light pulses reach the one atomic unit of time”, posted on arXiv on 2025 August 20. After the appearance of the preprint, we exchanged detailed comments with the authors regarding their analysis and the reported 19.2-as value, but fundamental disagreements remain unresolved. Because claims of world-record pulse durations carry broad implications for attosecond science, they must be supported by transparent and reproducible analysis. We therefore propose that the original streaking spectra be made publicly available and that independent groups be invited to analyze the data. Only through such open scrutiny can the validity of the claimed pulse duration be reliably established.