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Robert Ewing of the Pacific Northwest National Laboratory. | Photo Credit: Will Wetzel

In the first part of a three-part interview, Robert Ewing discusses the core technology behind the VaporID system, explains how the system differs from current IMS systems, and describes the challenges the team faced in miniaturizing the VaporID device into a portable, microwave-sized system.

Unsolved Problems in Spectroscopy - Part 1

This tutorial examines the modeling of diffuse reflectance (DR) in complex particulate samples, such as powders and granular solids. Traditional theoretical frameworks like empirical absorbance, Kubelka-Munk, radiative transfer theory (RTT), and the Hapke model are presented in standard and matrix notation where applicable. Their advantages and limitations are highlighted, particularly for heterogeneous particle size distributions and real-world variations in the optical properties of particulate samples. Hybrid and emerging computational strategies, including Monte Carlo methods, full-wave numerical solvers, and machine learning (ML) models, are evaluated for their potential to produce more generalizable prediction models.