Academic Appointments

  • Physical Science Research Scientist, Mechanical Engineering

Professional Education

  • PhD, Stanford University, Mechanical Engineering (2024)
  • MS, Stanford University, Mechanical Engineering (2020)
  • BS, The Pennsylvania State University, Nuclear Engineering (2018)

Contact

  • Academic
    sclees@stanford.edu
    University - Academic staff Department: Mechanical Engineering - Thermosciences Position: Physical Science Research Scientist

Additional Info

Current Research and Scholarly Interests

Laser diagnostics development for combustion applications

All Publications

  • A Rapidly Tunable Laser System for Measurements of NH2 at 597 nm Behind Reflected Shock Waves. Sensors (Basel, Switzerland) Clees, S., Barnes, S. C., Rault, T. M., Strand, C. L., Hanson, R. K. 2024; 24 (24)

    Abstract

    Distributed feedback lasers, which feature rapid wavelength tunability, are not presently available in the yellow and orange spectral regions, impeding spectroscopic studies of short-lived species that absorb light in this range. To meet this need, a rapidly tunable laser system was constructed, characterized, and demonstrated for measurements of the NH2 radical at 597.4 nm. The system consisted of three main parts: (1) a distributed feedback diode laser operating at 1194.8 nm, (2) a fiber-coupled optical amplifier, and (3) a periodically poled lithium niobate (PPLN) waveguide for second-harmonic generation. A phase-matching optical frequency bandwidth of 118 GHz and a second-harmonic generation efficiency of 109%/W were determined for the PPLN waveguide, and the intensity and wavelength stability of the system were measured. The rapid-tuning capabilities of the laser system were characterized to explore its potential for use in scanned-direct absorption and wavelength modulation spectroscopy experiments. The feasibility of scanned-direct absorption up to a scan rate of 900 kHz and wavelength modulation spectroscopy at modulation frequencies up to 800 kHz were demonstrated. Finally, the system was deployed in a series of shock tube experiments in which the concentration of NH2 radicals was measured during the decomposition of NH3 behind reflected shock waves.

    View details for DOI 10.3390/s24247920

    View details for PubMedID 39771657

    View details for PubMedCentralID PMC11679085

  • Simultaneous OH and OH* measurements during NH<sub>3</sub> oxidation in a shock tube PROCEEDINGS OF THE COMBUSTION INSTITUTE Clees, S., Rault, T. M., Zaczek, L. T., Hanson, R. K. 2024; 40 (1-4)

    View details for DOI 10.1016/j.proci.2024.105286

    View details for Web of Science ID 001258875400001

  • Multi-speciation and ignition delay time measurements of ammonia oxidation behind reflected shock waves COMBUSTION AND FLAME Rault, T. M., Clees, S., Figueroa-Labastida, M., Barnes, S. C., Ferris, A. M., Obrecht, N., Callu, C., Hanson, R. K. 2024; 260

    View details for DOI 10.1016/j.combustflame.2023.113260

    View details for Web of Science ID 001147344300001

  • Low-temperature oxidation of n-octane and n-decane in shock tubes: Differences in time histories of key intermediates COMBUSTION AND FLAME Choudhary, R., Clees, S., Boddapati, V., Shao, J., Davidson, D. F., Hanson, R. K. 2023; 251

    View details for DOI 10.1016/j.combustflame.2023.112670

    View details for Web of Science ID 000955844400001

  • A laser-absorption sensor for in situ detection of biofuel blend vapor in engine intakes PROCEEDINGS OF THE COMBUSTION INSTITUTE Clees, S., Cha, D. H., Biswas, P., Boddapati, V., Cassady, S. J., Strand, C. L., Hanson, R. K., French, B., Gilmour, A., Hawk, K. C., Stitt, J. M., Ferlet, X. 2023; 39 (1): 1307-1316

    View details for DOI 10.1016/j.proci.2022.07.110

    View details for Web of Science ID 001019044900001

  • Shock tube study of ethanol pyrolysis II: Rate constant measurements and modeling COMBUSTION AND FLAME Choudhary, R., Boddapati, V., Clees, S., Girard, J. J., Peng, Y., Shao, J., Davidson, D. F., Hanson, R. K. 2021; 233

    View details for DOI 10.1016/j.combustflame.2021.111554

    View details for Web of Science ID 000718900500002

  • Shock tube study of ethanol pyrolysis I: Multi-species time-history measurements COMBUSTION AND FLAME Choudhary, R., Boddapati, V., Clees, S., Girard, J. J., Peng, Y., Shao, J., Davidson, D. F., Hanson, R. K. 2021; 233

    View details for DOI 10.1016/j.combustflame.2021.111553

    View details for Web of Science ID 000718900500003

  • Measurement of time histories of stable intermediates during first stage ignition of n-heptane and its two isomers in a shock tube PROCEEDINGS OF THE COMBUSTION INSTITUTE Choudhary, R., Girard, J. J., Clees, S., Johnson, S. E., Shao, J., Davidson, D. F., Hanson, R. K., Aradi, A. A. 2021; 38 (1): 957-965

    View details for DOI 10.1016/j.proci.2020.06.296

    View details for Web of Science ID 000668626900026

  • ROLE OF TURBULENCE IN PRECESSING VORTEX CORE DYNAMICS Karmarkar, A., Frederick, M., Clees, S., Mason, D., O'Connor, J., ASME AMER SOC MECHANICAL ENGINEERS. 2019

    View details for Web of Science ID 000502164700010

https://orcid.org/0000-0002-5343-7084