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Simultaneous production of H − by both thermal and electron-stimulated desorptions from saline hydrides
To develop a compact negative ion source for solid samples, powder (∼10 mg ) of saline hydride (LiH, CaH 2 , or SrH 2 ) deposited on a molybdenum ribbon ( R, ∼0.1 cm 2 ) was heated up to ∼800 K , yielding the mass-analyzed current (i T − ≈10 −11 A ) of H − due to thermal desorption (TD) togethe...
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| Published in: | Review of Scientific Instruments 1998-02, Vol.69 (2), p.953-955 |
|---|---|
| Main Authors: | , , , , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | To develop a compact negative ion source for solid samples, powder
(∼10
mg
)
of saline hydride (LiH,
CaH
2
,
or
SrH
2
) deposited on a molybdenum ribbon (
R,
∼0.1
cm
2
) was heated up to
∼800
K
,
yielding the mass-analyzed current
(i
T
−
≈10
−11
A
)
of
H
−
due to thermal desorption (TD) together with the current
(I
−
≈10
−3
A
)
of thermal electron
(e
−
).
After the “activation” at
∼800
K
,
the work function (φ) of a
SrH
2
/Mo
system, e.g., was
7.3±0.3
eV
,
while the desorption energy
(E
−
)
of
H
−
due to TD was
9.7±0.4
eV
.
The value of
E
−
−φ=2.4±0.2
eV
,
thus determined agreed fairly with that (2.34 eV) evaluated thermochemically from our simple model. The sample vapor and
e
−
originating from the hydride continually condensed onto and impacted against, respectively, the ion-extraction slit plate mounted above
R,
thereby giving the current
(i
E
−
)
of
H
−
due to electron-stimulated desorption (ESD). In the case of
SrH
2
at 760 K,
i
E
−
was
∼30×
as large as
i
T
−
.
Our dual ion source yielded stable currents of
H
−
due to TD and ESD. |
|---|---|
| ISSN: | 0034-6748 1089-7623 |
| DOI: | 10.1063/1.1148601 |