XASVue Spectral Viewer: Web XAS Analysis

• XASVue Spectral Viewer is an interactive web-based application that visualizes and analyzes X-ray absorption spectroscopy data with standardized methods.
• It employs core data processing routines including normalization, background subtraction, and EXAFS extraction to support rapid spectral analysis.
• Designed for broad accessibility, it integrates client-side JavaScript with server-side Node.js and MongoDB to enable real-time, collaborative research.

XASVue Spectral Viewer is an interactive, browser-based application for the visualization and preliminary analysis of X-ray absorption spectroscopy (XAS) data, embedded within the XASDB web platform and designed for broad accessibility, standardized analysis, and collaborative research. It leverages web-centric technologies and integrates advanced data processing routines to support rapid inspection, normalization, background subtraction, and extended X-ray absorption fine structure (EXAFS) extraction across heterogeneous datasets in materials science, environmental research, chemistry, and biology (Spasyuk, 16 Sep 2025).

1. System Architecture and Platform Integration

XASVue is implemented as a pure client-side application using Vanilla JavaScript for direct Document Object Model (DOM) manipulation, paired with a Bootstrap CSS framework to achieve responsive layouts across all device types. The server-side infrastructure of XASDB—within which XASVue is embedded—utilizes Node.js for efficient, asynchronous data management and MongoDB as a document-oriented database to support the storage of diverse spectral formats and comprehensive metadata.

The viewer is tightly linked to the XASDB platform, which currently hosts more than 1000 reference spectra covering 40 elements and 324 chemical compounds. This design allows seamless real-time querying, data retrieval, visualization, and processing in web browsers without the need for local software installation or dedicated hardware, supporting cross-platform compatibility (Windows, macOS, Linux, tablets, smartphones).

2. Data Processing Capabilities

XASVue incorporates the XASproc JavaScript library, responsible for core signal processing functions traditionally associated with specialized desktop software (e.g., Athena, Larch). Key routines implemented in-browser include:

• Normalization of transmission-mode XAS data according to the Beer–Lambert law:

$$\mu(E) = \frac{1}{x} \ln \left(\frac{I_0}{I_t}\right)$$

where $I_0$ and $I_t$ are incident and transmitted intensities, and $x$ is sample thickness.

• Background subtraction, with both spline-based and weighted polynomial methods. Spline fitting leverages a control point parameterization:

$$N_{\mathrm{knots}} \approx 0.326 \, R_{\mathrm{bkg}} \left[ \sqrt{E_{\mathrm{max}}-E_0} - \sqrt{E_{\mathrm{min}}-E_0} \right]$$

Background quality is quantified using a Background Quality Score (BQS) that aggregates metrics such as k³-weighted mean offset, slope, symmetry, and variance.

• Edge determination and EXAFS extraction proceeds by locating the absorption edge $E_0$ through smoothed derivative maxima. The normalized EXAFS signal is:

$\chi(E) = \frac{\mu(E) - \mu_0(E)}{\Delta \mu_0}$

Conversion to wavenumber ($k$) uses:

$k = \sqrt{\frac{2m_e (E-E_0)}{\hbar^2}}$

where $m_e$ is electron mass, and $\hbar$ is the reduced Planck constant.

• k-weighting (e.g., k⁰, k¹, k², k³), Fourier transforms of $\chi(k)$ to R-space, application of Hanning or Kaiser windows for artifact suppression, and derivative calculations for feature enhancement.

This embedded suite of algorithms allows for rapid in-browser execution of normalization, background subtraction, and EXAFS analysis directly on reference or experimental spectra.

3. Usability and Accessibility

Engineered with an installation-free philosophy, XASVue is fully operable via modern web browsers and is responsive to device form factor due to Bootstrap CSS. This universal accessibility lowers entry barriers for users in multi-institutional and international contexts and simplifies access for educational activities or remote collaboration.

Server-side asynchronous operations and the document-based MongoDB approach provide high-performance handling of sizable collections of spectra and metadata. The real-time capabilities of Vanilla JavaScript enable immediate feedback for interactive tasks, such as spectrum manipulation, zooming, overlay, and parameter tweaking.

4. Analytical and Visualization Features

Users can load and inspect spectral data, apply processing workflows, and visualize key aspects of XAS—ranging from primary absorption edges to complex EXAFS oscillations. The viewer supports qualitative assessment, feature identification, and preliminary quantitative analysis analogous to desktop tools, but through a streamlined web interface.

The ability to overlay experimental and reference spectra, execute windowed Fourier analysis, and dynamically adjust weighting parameters is critical for comparing chemical environments, extracting radial pair distribution information, and facilitating materials fingerprinting.

A standardized output format and metadata annotation improve compatibility across research groups and ensure interoperable datasets for subsequent machine learning or linear combination fitting (LCF) workflows.

5. Collaborative, Educational, and Open Science Applications

XASVue is distributed under the Creative Commons Attribution 4.0 International License (CC BY 4.0), reflecting a commitment to open access and compliance with FAIR data principles: Findable, Accessible, Interoperable, and Reusable. The XASDB platform encourages user contributions and collaborative database expansion, supporting both routine research and advanced applications.

For educational purposes, XASVue provides a direct, hands-on tool to explore the principles of X-ray absorption, including normalization, edge detection, and Fourier transformation, without steep prerequisites in installation or data management. The interactive nature of the platform aids in training and pedagogical engagement.

In collaborative contexts, real-time data sharing and web-based analysis enable accelerated project development, support inter-laboratory reproducibility, and facilitate global engagement with high-quality standardized XAS datasets.

6. Impact and Future Directions

The deployment of XASVue has advanced the accessibility and utility of XAS data analysis in materials science, chemistry, biology, and environmental sciences. Its rapid normalization, extraction, and visualization of EXAFS features support routine fingerprinting and complex compound characterization, comparable to established desktop solutions.

A plausible implication is that the browser-based model, combined with advanced signal processing and open access, will foster increased integration of XAS with machine learning techniques, further accelerating materials discovery and automated structure identification. XASVue’s model is positioned to serve as a template for future web-centric scientific platforms, streamlining high-throughput data analysis and interdisciplinary collaboration.

7. Comparison with Traditional Analysis Workflows

Unlike traditional desktop programs that require installation and local data management (e.g., Athena, Larch, SIXPack), XASVue delivers equivalent analytical power directly through the browser. By embedding data processing capabilities in JavaScript and integrating seamlessly with a scalable web architecture, it eliminates bottlenecks in setup and maintenance.

This approach is particularly advantageous in multi-user environments, open repositories, and resource-constrained settings, enabling broad and equitable participation in advanced spectroscopic research and education.