Reply to "Comment on Brilliant source of 19.2 attosecond soft X-ray pulses below the atomic unit of time" by Han (arXiv:2510.17949)

TL;DR

This paper defends the validity of a 19.2 attosecond soft X-ray pulse measurement against critiques, clarifying experimental conditions and addressing misconceptions about the original analysis.

Contribution

The authors provide a detailed rebuttal to a comment challenging their attosecond pulse measurement, reaffirming the accuracy of their previous results with clarified experimental context.

Findings

The 19.2 attosecond pulse measurement is valid under the specified experimental conditions.

Misinterpretations in the critique are addressed and corrected.

The original measurement aligns with established metrological standards.

Abstract

We recently reported a refine analysis of a previously conducted soft X-ray (SXR) attosecond streaking measurement [1], employing the Variational Phase Gradient Temporal Analysis (VPGTA) retreival algorithm [2]. This re-evaluation, prompted by new metrological insights, revealed a 19.2 attosecond pulse - consistent with the expectations and estimates of our earlier work [3]. Shortly thereafter, a comment by M. Han [4] challenged our findings, citing "physical and technical issues concerning the original experiment and the new characterisation" inclusing purported contributions from Auger electrons, unfiltered low-energy harmonics, and uncompensated intrinsic chirp. These concerns, however, stem from misinterpretation of the experimental regime, selective citation of context, and disregard for well-established results in the peer-reviewed literature. In this reply, we address and clarify these points, demonstrating that the issues raised are not relevant under our experimental conditions. Given the highly specialized nature of attosecond genertaion and metrology in the soft X-ray water-window regime, we consider it essential to clarify these aspects of different regimes and reaffirm teh validity of our conclusions.