A&A Supplement series, Vol. 128, March I 1998, 361-362
Received July 7; accepted July 11, 1997
J.-Y. Roncin
and F. Launay
Laboratoire Traitement du Signal et Instrumentation (TSI),
CNRS UMR 5516,
23 rue du Dr. Paul Michelon, 42023
Saint-Étienne Cedex 2, France
Observatoire de Paris, Section de Meudon, DAMAp and CNRS URA 812,
92195 Meudon Cedex, France
Observed wavenumbers of the emission lines belonging to 10
vacuum ultraviolet band systems of molecular nitrogen are classified into 283
bands, 220 of them reported for the first time
.
keywords: molecular data -- planets and satellites: general
The vacuum ultraviolet (VUV) emission spectrum of molecular nitrogen
(N2) is of great astrophysical interest. The spectra transmitted from
the Voyager 1 and 2 spacecrafts (Broadfoot et al. 1981, 1989;
Strobel & Shemansky 1982) have
shown that N2 is the major constituent not only of the Earth's atmosphere, but
also of those of Titan and Triton, satellites of Saturn and Neptun respectively.
The present paper aims at presenting an extensive set of line wavenumbers for the
bands involving transitions toward the electronic ground state 
from 10
singlet electronic excited states of N2, i.e.
from the valence states 
,
, and 
, and the Rydberg states 
, 
,
,
,
,
,
and 
. In
parentheses we have recalled the traditional names of the states. This paper
complements another publication by Roncin et al.
(1998) where they report
the energies for the rovibronic levels of the ten excited states.
The use of a low-pressure Penning-type electric discharge has led to
considerably reduced self-absorption at short wavelengths, extending and greatly
improving previously published data of
Tilford & Wilkinson (1964). Tables 1 to
10 list all the observed rotational branches of the 283 bands belonging to the
10 band systems 
,
,
,
,
,
,
,
,
,
and 
(Lyman-Birge-Hopfield), respectively. All VUV transitions
terminate on the electronic ground state
and an abbreviated notation
will be used to identify the transitions,
e.g. b(2-7) instead of 
(v'=2)
.
The tables are organized as follows:
The first column gives the rotational quantum number J of the electronic
ground state. The corresponding R and P branch lines of the 
transitions are
listed in the second and third columns and the R, Q, and P
branch lines of the
transitions are listed in the second,
third, and fourth columns. An asterisk
is used to identify blended lines that have been assigned more than once, or
to indicate, in the case of a missing line, that a feature has been observed
within 1.2 and 2 cm-1 from the missing transition.
Because the pressure in the light source is still too high to prevent completely self-absorption at short wavelengths, most of (v', v''=0) bands are missing. However, high-J lines are showing up for several of them. Moreover, a number of emission lines are weakened or missing because they coincide with one or several absorption lines. For many missing lines we have written, in the same column, the name of the molecular absorption lines preventing the emission from being seen. Some missing lines could not be measured because they are overlapped by a strong atomic line which is identified in this column. For the few bands previously reported (Roncin et al. 1984, 1989) one may note slight discrepancies with presently reported wavenumber values. This is because present values are averaged over several measurements, contrary to the previously published data.