EGAS41 - Swansea University

41 st EGAS CP 208 Gdańsk 2009
Reanalysis of the A 1 Π–X 1 Σ + bands system of the 13 CD + ion
radical
R. Hakalla ∗ ,, M. Zachwieja, W. Szajna ∗ , R. Kȩpa
Atomic and Molecular Physics Laboratory, Institute of Physics University of Rzeszów,
35-959 Rzeszów, Poland
∗ Corresponding author: hakalla@univ.rzeszow.pl
In the 13 CD + isotopic ion radical spectra of the A 1 Π–X 1 Σ + bands system have been
obtained. Emission spectra of the bands were observed in the 22800–25100 cm −1 spectral
region using a conventional spectroscopic technique. The 13 CD + molecules were produced
by an electric discharge in an aluminum water-cooled hollow-cathode lamp, operated at
400 V and 180÷200 mA DC. Nonflowing mixture of 3 Torr of He carried gas and 1 Torr of
13 C 2 D 2 was found as optimal for production of strong A 1 Π–X 1 Σ + emission. The spectra
were observed in the 6th order with the 2-m Ebert plane grating PGS-2 spectrograph
equipped with 651-grooves/mm grating with a total number of grooves of 45 600, blazed
at 1.0 µm. The reciprocal dispersion was in the range 0.066–0.075 nm/mm and theoretical
resolving power was about 270 000. The spectrum of 13 CD + was recorded by translating
on a linear stage an exit slit and photomultiplier tube (HAMAMATSU R943-02) along
the focal curve of the spectrograph. The entrance and exit slit widths were 0.035 mm.
The line intensities were measured by a single photon counting (HAMAMATSU C3866
photon counting unit and M8784 photon counting board) with a counter gate time of 50-
500 ms (no dead time between the gates) depending on spectrum intensity. Positions of
the exit slit were measured using He-Ne laser interferometer synchronized with the photon
counting board (during the counter gate time the position is measured 64 times and a
mean value with the counts number are transmitted to PC as a measurement point). The
total number of the measurement points was about 73 000 for one scan with the sample
step of 3 µm (sample step it is the translation of the exit slit during the counter gate time).
Simultaneously recorded some thorium atomic lines [1] obtained from several overlapped
orders of the spectrum from a water-cooled hollow-cathode tube were used for absolute
wavenumber calibration. For the wavenumber calculations seventh-order interpolation
polynomials were used. The typical standard deviation of the least-squares fit for the
70-80 calibration lines was about 0.0012–0.0016 cm −1 . The calibration procedure was
tested (with two Th lamps simultaneously – one as an examination light source and the
second one to provide the reference spectrum) to be ±0.0015 cm −1 . Comparison of the
wavenumbers of the 0–0 band obtained in this study with those of [2] shows differences
(about 0.015–0.020 cm −1 ) of both wavenumber values. Finally we improved molecular
constants for both electronic states: A 1 Π as well as X 1 Σ + by means of the direct fit. Till
nowadays only one experimental publication discussing 13 CD + ion molecule appeared [2].
References
[1] B.A. Palmer and R. Engleman Jr., Atlas of the Thorium Spectrum, (Los Alamos
National Laboratory, Los Alamos NM 1983) - unpublished
[2] Z. Bembenek, J. Mol. Spectrosc. 182, 439-443 (1997)
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