arXiv subjects

Ya-Chu Chan

Publications and source records attributed to Ya-Chu Chan.

3 recordsLinked to original sources

arXiv2024

Observation of full contrast icosahedral Bose-Einstein statistics in laser desorbed, buffer gas cooled C$_{60}$

The quantum mechanical nature of spherical top molecules is particularly evident at low angular momentum quantum number J. Using infrared spectroscopy on the 8.4$μ$m rovibrational band of buffer gas cooled $^{12}$C$_{60}$, we observe the hitherto unseen R(J = 0 - 29) rotational progression, including the complete disappearance of certain transitions due to the molecule's perfect icosahedral symmetry and identical bosonic nuclei. The observation of extremely weak C$_{60}$ absorption is facilitated by a laser desorption C$_{60}$ vapor source, which transfers 1000-fold less heat to the cryogenic buffer gas cell than a traditional oven source. This technique paves the way to cooling C$_{60}$ and other large gas phase molecules to much lower temperatures, providing continued advances for spectral resolution and sensitivity.

physics.atom-ph↗

arXiv2023

Breath analysis by ultra-sensitive broadband laser spectroscopy detects SARS-CoV-2 infection

Rapid testing is essential to fighting pandemics such as COVID-19, the disease caused by the SARS-CoV-2 virus. Exhaled human breath contains multiple volatile molecules providing powerful potential for non-invasive diagnosis of diverse medical conditions. We investigated breath detection of SARS-CoV-2 infection using cavity-enhanced direct frequency comb spectroscopy (CE-DFCS), a state-of-the-art laser spectroscopic technique capable of a real-time massive collection of broadband molecular absorption features at ro-vibrational quantum state resolution and at parts-per-trillion volume detection sensitivity. Using a total of 170 individual breath samples (83 positive and 87 negative with SARS-CoV-2 based on Reverse Transcription Polymerase Chain Reaction tests), we report excellent discrimination capability for SARS-CoV-2 infection with an area under the Receiver-Operating-Characteristics curve of 0.849(4). Our results support the development of CE-DFCS as an alternative, rapid, non-invasive test for COVID-19 and highlight its remarkable potential for optical diagnoses of diverse biological conditions and disease states.

physics.med-ph↗

arXiv2021

Ultra-sensitive multi-species spectroscopic breath analysis for real-time health monitoring and diagnostics

Breath analysis enables rapid, non-invasive diagnostics, as well as long-term monitoring, of human health through the identification and quantification of exhaled biomarkers. Here, for the first time, we demonstrate the remarkable capabilities of mid-infrared (mid-IR) cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) applied to breath analysis. We simultaneously detect and monitor as a function of time four breath biomarkers - CH$_3$OH, CH$_4$, H$_2$O and HDO - as well as illustrating the feasibility of detecting at least six more (H$_2$CO, C$_2$H$_6$, OCS, C$_2$H$_4$, CS$_2$ and NH$_3$) without modifications to the experimental apparatus. We achieve ultra-high detection sensitivity at the parts-per-trillion level. This is made possible by the combination of the broadband spectral coverage of a frequency comb, the high spectral resolution afforded by the individual comb teeth, and the sensitivity enhancement resulting from a high-finesse cavity. Exploiting recent advances in frequency comb, optical coating, and photodetector technologies, we can access a large variety of biomarkers with strong carbon-hydrogen bond spectral signatures in the mid-IR.

physics.chem-ph↗