講演情報
[15p-K304-2]Probing Gaseous Photothermal Effects using Background-free Vibrational Dispersion Spectroscopy
〇WENQING SONG1, KOKORO FUJIWARA1, IKKI MORICHIKA1, SATOSHI ASHIHARA1 (1.IIS, The Univ. of Tokyo)
キーワード：
molecular vibrational spectroscopy、photothermal effect、mid-infared laser application
Photothermal spectroscopy in gaseous media has emerged as a promising technique for sensitive molecular detection by probing thermodynamic changes, such as variations in temperature, pressure, volume, and density, induced by resonant photoexcitation. However, the underlying thermodynamic processes responsible for refractive index changes, typically probed at non-resonant wavelengths, remain poorly understood. In this work, we employ the recently developed background-free vibrational dispersion spectroscopy to quantitatively characterize photothermal density changes while distinguishing individual molecular species in gas mixtures. Utilizing a Cr:ZnS mode-locked femtosecond laser, the method enables quantitative measurement of both steady-state and dynamic density variations. Experimental results targeting methane combination tones around 2300 nm reveal background-free absorption spectra, time-averaged molecular dispersion representing a new equilibrium state, and photothermal modulation amplitudes. These findings highlight the method's capability to provide detailed insights into photothermal dynamics, offering a versatile platform for exploring diverse thermodynamic processes, including photothermal phenomena, combustion reactions, and synthetic reactions.