23 research outputs found
Absorption spectrum in the wings of the potassium second resonance doublet broadened by helium
We have measured the reduced absorption coefficients occurring in the wings
of the potassium 4S-5P doublet lines at 404.414 nm and at 404.720 nm broadened
by helium gas at pressures of several hundred Torr. At the experimental
temperature of 900 K, we have detected a shoulder-like broadening feature on
the blue wing of the doublet which is relatively flat between 401.8 nm and
402.8 nm and which drops off rapidly for shorter wavelengths, corresponding to
absorption from the X doublet Sigma+ state to the C doublet Sigma+ state of the
K-He quasimolecule. The accurate measurements of the line profiles in the
present work will sharply constrain future calculations of potential energy
surfaces and transition dipole moments correlating to the asymptotes He-K(5p),
He-K(5s), and He-K(3d).Comment: 2 figure
Soft Argon–Propane Dielectric Barrier Discharge Ionization
Dielectric
barrier discharges (DBDs) have been used as soft ionization
sources (DBDI) for organic mass spectrometry (DBDI-MS) for approximately
ten years. Helium-based DBDI is often used because of its good ionization
efficiency, low ignition voltage, and homogeneous plasma conditions.
Argon needs much higher ignition voltages than helium when the same
discharge geometry is used. A filamentary plasma, which is not suitable
for soft ionization, may be produced instead of a homogeneous plasma.
This difference results in N<sub>2</sub>, present in helium and argon
as an impurity, being Penning-ionized by helium but not by metastable
argon atoms. In this study, a mixture of argon and propane (C<sub>3</sub>H<sub>8</sub>) was used as an ignition aid to decrease the
ignition and working voltages, because propane can be Penning-ionized
by argon metastables. This approach leads to homogeneous argon-based
DBDI. Furthermore, operating DBDI in an open environment assumes that
many uncharged analyte molecules do not interact with the reactant
ions. To overcome this disadvantage, we present a novel approach,
where the analyte is introduced in an enclosed system through the
discharge capillary itself. This nonambient DBDI-MS arrangement is
presented and characterized and could advance the novel connection
of DBDI with analytical separation techniques such as gas chromatography
(GC) and high-pressure liquid chromatography (HPLC) in the near future