Environmental influence on the IR fluorescence of Xe2* molecules in electron beam excited Ar–Xe mixture at high density

Abstract

Abstract. We report new measurements of the near infrared (NIR) Xe * 2 excimer fluorescence in an electronbeam-excited Ar (90%)-Xe (10 %) mixture at room temperature. Previous measurements up to a density N ≈ 2 × 10 26 m −3 discovered a broad excimer fluorescence band at ≈ 7800 cm −1 , whose center is redshifted by increasing N (A. F. Borghesani, G. Bressi, G. Carugno, E. Conti, and D. Iannuzzi, J. Chem. Phys., 115, 6042 (2001) [1]). The shift has been explained by assuming that the energy of the optical active electron in the molecule is shifted by the density-dependent Fermi shift and by accounting for the solvation effect due to the environment. We have extended the density range up to N ≈ 6 × 10 26 m −3 , confirming the previous measurements and extending the validity of the interpretative model. A detailed analysis of the width of the fluorescence band gives a value of 2.85 nm for the size of the investigated excimer state. Such a large value lends credence to the validity of the proposed explanation of the experimental findings.

Infrared luminescence of Xe<inf>2</inf> excimers produced by electron impact in dense gas

“…3. The present data agree very well with the previous data [26,30] in the restricted range in which they overlap.…”

“…Preliminary results obtained for P up to 2.4 MPa in the ArXe mixture have already been published [30]. We report here the extension of the measurement range up to 3.3 MPa in both the pure gas and in the mixture.…”

Intense infrared scintillation of liquid Ar-Xe mixtures

“…Whether this line is responsible for the 1.18 µm emission (observed in the liquid phase) and just shifted to this wavelength position, or completely new energy transfer mechanisms have to be invoked to explain the 1.18 µm band, will have to be studied in the future. An emission feature in dense gaseous Ar-Xe mixtures found by Borghesani and coworkers [37,38] is very similar in shape and with 1.3 µm peak wavelength close to the emission at 1.18 µm found here. However, a simple density related effect shifting the emission to shorter wavelengths seems unlikely since the emission is redshifted with increasing pressure [37,38].…”

“…An emission feature in dense gaseous Ar-Xe mixtures found by Borghesani and coworkers [37,38] is very similar in shape and with 1.3 µm peak wavelength close to the emission at 1.18 µm found here. However, a simple density related effect shifting the emission to shorter wavelengths seems unlikely since the emission is redshifted with increasing pressure [37,38]. The 1.3 µm emission was observed in pure xenon as well as in argon with a 10 % xenon admixture and was attributed to Xe * * 2 by the authors of refs.…”

Infrared emission spectrum and potentials of 0+uand 0+gstates of Xe2excimers produced by electron impact

“…In the limit of low P,ν m and Γ are the same both in the pure gas and in the mixture. Without any further inquiries, as we were interested on the excimer interaction with the high density environment [29], we attributed the emission to a Xe 2 boundfree transition between a state dissociating into the 5p 5 6p manifold and one of 5p 5 6s configuration [27]. Upon improving our experimental technique, especially using a LN 2 -cooled InSb photodiode detector, we have been able to make high-resolution time-integrated measurements of the excimer IR emission that allow for the first time a more precise assignment of the molecular states involved in the transition.…”