EGAS41 - Swansea University

41 st EGAS CP 10 Gdańsk 2009
IR luminescence of Xe 2 excimers produced in dense Xe gas by
electron impact
A.F. Borghesani 1,2 , G. Carugno 2
1 Dept. of Physics, University of Padua, and CNISM unit
2 Istituto Nazionale di Fisica Nucleare
via Marzolo 8, I-35131 Padua, Italy
∗ Corresponding author: borghesani@padova.infm.it,
We discovered the emission of an infrared (IR) continuum centred at 1.3 µm (˜ν ≈ 7800
cm −1 ) due to the decay of Xe 2 excimers produced in dense Xe gas excited by 70-keV
electrons [1].
0.5
1.2
0.4
1
7600
Ar-Xe
I (arb. un.)
0.3
0.2
0.8
0.6
0.4
7200
6800
0.1
0.2
6400
Xe
0.0
0
6000 7000 8000 9000 10000 11000
~
(cm -1 )
0 1 2 3 4 5 6 7 8
N (10 26 m 3 )
Figure 1: Left: Xe 2 IR emission spectrum. Thick line: FC calculations. Right: Density dependence
of the peak wavenumber in pure Xe gas and in an Xe–Ar mixture.
In the left panel of Fig. 1 we show the spectrum for P = 0.1 MPa. The continuum
is due to a bound–free transition between the 0 + u state related to the 6p( 1 D 2 ) atomic
limit and the 0 + g dissociative one related to the 6s(3 P 1 ) limit. This assignment reproduces
the spectrum shape by means of Franck–Condon calculations [2]. A unique feature of
the spectrum is that the wavenumber of its peak ν m is red-shifted as the gas density
N increases. In the right panel of Fig.1 ν m is plotted vs N for P ≤ 3.3 MPa in pure
Xe gas and in an Ar-Xe mixture. The shift is explained by accounting for the dielectric
properties of the gas and the quantum multiple scattering of the optically active electron
whose wavefunction extends over many atoms [1].
References
[1] A.F. Borghesani, G. Bressi, G. Carugno, E. Conti, D. Iannuzzi, J. Chem. Phys. 115,
6042 (2001)
[2] A.F. Borghesani, G. Carugno, I. Mogentale, J. Phys. B: At. Mol. Opt. Phys. 40,
4551 (2007)
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