Abstract

In this paper photothermal deflection spectroscopy (PDS) is used to measure ethylene in nitrogen in a flowing stream with velocities high enough (>100 cm/sec) that forced convection dominates over thermal conduction in the heat flow. The PDS signal was found to be linear in ethylene concentration and pump laser power and varied inversely with gas velocity. It was also measured as a function of the relative position of the laser beam waists with respect to each other and with respect to the position of the tube from which the gas flowed. The energy equation for this system was solved analytically for the case of a steady-state temperature and numerically for the more general time-dependent case. The resulting calculations of signal as a function of time compare very well with experiment. This technique has the advantages of high sensitivity (1 ppm in the present conditions), good spatial resolution, and is nonintrusive.

© 1984 Optical Society of America

Gas velocity measurements using photothermal deflection spectroscopy

Jeffrey A. Sell
Appl. Opt. 24(22) 3725-3735 (1985)

Measurements of very low gas flow velocities by photothermal deflection spectroscopy

Y.-X. Nie, K. Hane, and R. Gupta
Appl. Opt. 25(18) 3247-3252 (1986)

Pulsed photothermal deflection spectroscopy in a flowing medium: a quantitative investigation

A. Rose, Reeta Vyas, and R. Gupta
Appl. Opt. 25(24) 4626-4643 (1986)

Linear imaging of gas velocity using the photothermal deflection effect

Jeffrey A. Sell and Robert J. Cattolica
Appl. Opt. 25(9) 1420-1428 (1986)

Continuous wave photothermal deflection spectroscopy in a flowing medium

Reeta Vyas, B. Monson, Y-X. Nie, and R. Gupta
Appl. Opt. 27(18) 3914-3920 (1988)