Is the Rotational Temperature of OH(A–X) for Discharges in and in Contact with Liquids a Good Diagnostic for Determining the Gas Temperature?

Abstract

In this paper the rotational temperature of OH(A–X) and rotational population distribution of OH(A) are investigated for streamer discharges in bubbles and glow discharges with liquid electrodes, both at atmospheric pressure. The influence of the filling gas is investigated in detail and the non‐Boltzmann nature of the rotational population distributions is discussed. It is shown that the rotational population distribution of OH(A) is even at atmospheric pressure an image of the formation process or is at least influenced by it. As a consequence the rotational temperature is in this case not a good estimate of the gas temperature as the rotational population distribution is not an image of a kinetic temperature. In some cases rotational states with small rotational numbers offer a possibility to obtain the gas temperature. The influence of these results on the determination of gas temperatures in the field of liquid plasmas is discussed.

Plasma Polymerization of 3‐Aminopropyltrietoxysilane (APTES) by Open‐Air Atmospheric Arc Plasma Jet for In‐Line Treatments

“…in the range of 600–1000 K are significantly lower that the rotational one. This behavior is in agreement with the work of Bruggeman et al where the authors concluded that OH rotational temperature depends also on the formation process of such radicals . Although OH (A–X) transition is usually not considered as a good thermometer to determine the vibrational temperature, simulations of the experimental spectra indicate that T vib ∼ 4000 ± 300 K, which is consistent with the previous values reported on CN radicals in a similar discharge …”

Rotational temperatures of N2(C,0) and OH(A,0) as gas temperature estimates in the middle pressure Ar/O2 discharge

“…However, in several works (e.g. [12,13]), where the rotational relaxation frequency was considerably higher than in our case, it has been found that OH(A,0) rotational population distribution is characterized by two values of T Rot . A study of this phenomenon was carried out in [13], (p=760 Torr, glow discharge with a water electrode) in different media.…”

Atmospheric Pressure Low Temperature Direct Plasma Technology: Status and Challenges for Thin Film Deposition

“…However, it is worth mentioning here the case of OH(A–X), which is more often questionable, although it is sometimes used with success 75, 76. Despite the AP, in fact, the rotational structure of the excited state (A) of OH can be influenced by its process of formation,77, 78 which means that the rotational temperature of OH(A–X) can sometimes not be considered a kinetic temperature.…”