A vacuum ultraviolet atomic beam light source
by Glenn Alden Govertsen
A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE in Physics
Montana State University
© Copyright by Glenn Alden Govertsen (1969)
Abstract:
An atomic beam light source designed and constructed primarily for the vacuum ultraviolet is
described. The light source produced spectra of argon and air in the extreme ultraviolet. A study was
made of the excitation functions of the Ar II lines at 920 Å and 932 Å. Also included is an unexpected
pressure dependence of the Ar I resonance lines. In presenting this thesis in partial fulfillment of the■require­
ments for ,an advanced degree at Montana State University, I agree that
the library shall make it freely available for inspection.
I further
agree that permission for extensive copying of this thesis for. scholarly
purposes .may be granted.by my.major professor, or, in his absence, by
the Director of Libraries.
It is understood that any copying or publica­
tion of this thesis for financial gain shall not be allowed without my
written permission.
Signature
Date
O
A VACUUM ULTRAVIOLET ATOMIC BEAM LIGHT SOURCE
' by
GLENN ALDEN GOVERTSEN
A t h e s i s s u b m i t t e d to the Graduate F a c u l t y
f u l f i l l m e n t o f the re quire m en ts f o r the
of
MASTER OF SCIENCE
i n
Physics
Approved:
----- /
H ea d5 M a j o r DefjlarJlm^ht
C h a i r m a n 5 E x a mi n i n g
Commi t t ee
MONTANA STATE UNIVERSITY
Bozeman 5 Montana
A u g u s t , 1969
in p a r t i a l
d e gr e e
ACKNOWLEDGEMENTS
I wish
t o t h a n k Dr.
D. K. An d e r s o n f o r
of developing
this
understanding
t h e p r o b l e ms
aspects
electronics,
Ch e r i
beam l i g h t
source.
posed and i n
Hi s
designing
o f t h e a p p a r a t u s was i r r e p l a c e a b l e .
e x p r e s s my t h a n k s
current
atomic
the o p p o r tu n ity
to
Fr ed B l a n k e n b e r g f o r
especially
in
regulator..
A fina l
Govertsen, fo r
doi ng
in
various
I a l s o want t o
his
the c o n s t r u c t i o n
help
of
help
in
the
t h e anode
word o f t h a n k s go t o my w i f e ,
t h e a r t wor k on a l l
the drawings.
TABLE OF CONTENTS
Chapter
Page
ABSTRACT................... ■................................... ■.
I .
II .
III.
.
.
.
vi
I NTRODUCTI ON...........................................-■.....................
I
T HE ORY ...................................................................................?
3
EXPERIMENTAL PROCEDURE . . . .
5
........................
Apparatus D e s c r i p t i o n
................... ■.....................
5
The At omi c B e a m ....................................................
5
The E l e c t r o n G u n ........................................................
8
D e t e c t i o n System ....................................................
11
Vacuum S y s t e m ..............................................................................11
IV.
MEASUREMENTS AND R E S U L T S ....................................... .*
13
I n i t i a l Experiments
. . . . . . . . . . .
13
Secondary E l e c t r o n E f f e c t
. . . . . . . .
16
E x c i t a t i o n F u n c t i o n s ................................................16
P r e s s u r e Dependence o f t h e Ar I Resonance
L i n e s ......................................................................................................16
V.
CONCLUSION ............................................
APPENDIX
. . . . . .
........................ ■..........................
. LITERATURE CITED ........................................................
24
25 .
■ 30
-V-
LI ST OF*FIGURES
Page
1 ..
The A t o m i c Beam L i g h t
2.
Cross
Section
of
Sour c e
. ■.
t h e A t o m i c Beam L i g h t So u r c e
3 . = Electron
Gun A s s e m b l y ...........................
4.
Spectral
Scan w i t h
5.
Spectral
Scan w i t h
6 . ' Intensity
7.
vs.
.. ......... ......... ...........
Current
f o r Ar
II
. . .
7
9
Argon B e a m .......................................
A ir Molecular
6
.
.
14
Beam . . .............................. 15
. . .
............................
17
E x c i t a t i o n F u n c t i o n s o f 920 K and 932 A L i n e s o f
Argon 1 1 ...................................... • ............................... ' ■. .' . .
.
18
8.
Intensity
vs. Pressure
for
1 0 4 8 . 2 2 A o f Ar gon
I .
.
19
9..
Intensity
vs. Pressure
for
1 0 6 6 . 6 6 A o f Ar gon
I . ■.
20
. .
21
.10.
11.
Ratio of
I n t e n s i t i e s vs. P r e s s u r e f o r Ar gon
C ollim ation
I
.
.
o f an A t o m i c B e a m ................................................27
- vi -
ABSTRACT
An a t o m i c beam l i g h t s o u r c e d e s i g n e d and c o n s t r u c t e d
p r i m a r i l y f o r t h e vacuum u l t r a v i o l e t i s d e s c r i b e d .
The l i g h t
s o u r c e p r o d u c e d s p e c t r a o f ar g o n and a i r i n t h e e x t r e me
u ltra v io le t.
A s t u d y was made o f t h e e x c i t a t i o n f u n c t i o n s o f
t h e Ar 11 l i n e s a t 920 A and 932 A.
A l s o i n c l u d e d i s an
u n e x p e c t e d p r e s s u r e dependence o f t h e Ar I r e s o n a n c e l i n e s .
I.
INTRODUCTION
The p a s t decade shows an i n c r e a s e
wor k done w i t h
are found
in
gaseous
1942.
atomic
beams.
in
the
experimental
Some e a r l i e r
Bassey and Si mpson^
references
r e v i e w some o f t h e
t h e n c u r r e n t wor k i n m o l e c u l a r beams.
A l s o , Mack and
2
Barkofsky
d e s c r i b e v a r i o u s a s p e c t s o f d e s i g n and use o f
gaseous
atomic
found d e a l i n g
Zacharias
3
beam a p p a r a t u s .
with
this
No f u r t h e r
subject
until
of molecular
by R. W. S t a n l e y ^
1960 i s
references
1956.
t h e n d e s c r i b e many e x p e r i m e n t a l
and new a p p l i c a t i o n s
in
t o gaseous a t o m i c
lite ra tu re
beams.
the f i r s t
is
Ki n g and
beam t e c h n i q u e s
A paper d e l i v e r e d
o f a g r o w i n g number o f
beams.
The r e c e n t wor k shows a v a r i e t y
of
techniques.
Odintsov
provides
information
on t h e use o f an a t o m i c beam as a l i g h t
source.
He p r e s e n t s
a discussion
and o f D o p p l e r w i d t h s
of
spectral
lig h t
source.
using
a new c o l l i m a t i on t e c h n i q u e .
collim ator
Hanes^ a l s o
and o t h e r s
w ill
o f beam s o u r c e c o l l i m a t i o n
lines
describes
an a t o m i c
be d i s c u s s e d
Kleinpoppen,
K r u g e r and Ul mer
beam w i t h
electrons
study
also
studies
beam.
Bal mer s p e c t r a l
More r e c e n t l y ,
s t r u c t ! o n . o f an a t o m i c
Larson
I0
beam s o u r c e
separately
7
excite
in
lines
using
beam l i g h t
an a t o m i c
techniques
the
basis
Stoner
O
hy dr ogen
and con -
s o u r c e by S t a n l e y
provide
a late r
a Hydrogen
the Balmer-a r a d i a t i o n .
the e x p e rim e n ta l
a t Purdue U n i v e r s i t y
f r o m such a
Hi s m u l t i - c h a n n e l e d
section.
to
obtained
for
9 10
5
and
the
lig h t
- 2-
source b u i l t
her e a t Montana S t a t e
U niversity.
Much o f t h e g e o me t r y o f S t a n l e y ' s
into
our d e s i g n .
that
the p h y s i c i s t s
The use o f
produces
etched
high
increasing
at
copper f o i l s
beam d e n s i t i e s
in
the p r o d u c t i o n
incorporated
t h e c o l l i m a t i on syst em
forming
the atomic
an " a i m e d "
the e x c i t a t i o n
This
is
technique
beam.
beam
region w ithout
has been used
o f an Ar gon beam i n
t h e MSU
source.
comes i n
the s p e c t r a l
Most o f
at
u ltra v io le t
in
this
atomic
The t i t l e
of
atomic
un der
beam s o u r c e a t MSU
investigation.
This
far
has been w i t h
study
region.
the resonance
1 0 4 8 . 2 2 A and 1 0 6 7 . 6 6 A ^ 5 and t h e
9 1 9 . 7 8 A and 9 3 2 . 0 5 A ^
lines
the
t h e e x t r e m e vacuum u l t r a v i o l e t
t h e wo r k done t h u s
o f Ar gon I ,
emission
in
region
concerned m a i n l y w i t h
lines
in
in
load.
The m a j o r d i f f e r e n c e
is
is
Purdue p r o d u c e d f o r
t h e pumpi ng
successfully
lig h t
Most n o t e w o r t h y
sources
lines
o f Ar gon I I .
spectral
beam l i g h t
a pa p e r
in
r e g i o n we have a vacuum
source.
a Soviet journal
a different
t y p e o f vacuum u l t r a v i o l e t
constructed.
I2
•
an e l e c t r o n
beam i s
Apparently
Thus by p r o d u c i n g
lig h t
an u l t r a s o n i c
the source of
indicates
s o u r c e has been
gas j e t
radiation.
that
excited
by
II.
Several
considerations
THEORY
are i m p o r t a n t
in
understanding
t h e u s e f u l n e s s and e f f e c t i v e n e s s o f an a t o m i c beam s o u r c e ,
q
Stanley
d e f i n e s the r a d ia n c e o f a s p e c t r a l l i n e , o f
w a v e l e n g t h X , as
Bx = c Qx / n ( x )
Here c i s
n(x)
a constant;
and j e ( x ) a r e
density.
tion.
j e ( x ) dx .
Qx i s
the atomic
The c o o r d i n a t e
A very d e t a i l e d
included
discussed
atomic
in S tan le y's
here,
9
derivation
n(x)
w ill
and
both n ( x )
flux
of observa­
and j e ( x ) i s
points
be c a l c u l a t e d
for
w ill
be
t h e MSU
beam s o u r c e .
of
o f an i n d i v i d u a l
channel
width.
the geometry o f
of
the
source are
the m u lt i- c h a n n e le d
channel.
o c c u r s when t h e mean f r e e
using
the d i r e c t i o n
of
section;
and e l e c t r o n
p a p e r . ■ Onl y s e l e c t e d
and o n l y
the t r a n s m i t t a n c e
single
cross
number d e n s i t y
x denotes
The i m p o r t a n t a s p e c t s
width
the e x c i t a t i o n
path o f
t h e c o l l i m a t i on,
collim ator
and t h e
The maximum beam d e n s i t y
t h e gas atoms
The f o l l o w i n g
rela tion
is
equals
t he
derived
t h e p r e s e n t s o u r c e and i t s . c o l l i m a t i n g
assembly.
n
=
.
.
.
I
n
GCoAa
See t h e A p p e n d i x f o r
is
the d e r i v a t i o n
t h e maximum number d e n s i t y
mittance;
C is
in
the
t h e c o l I i m a t i on'; o i s
of t h i s
result.
beam; T i s
a cross
Here n
the t r a n s ­
section
invo l ving
-4-
the e f f e c t i v e
channel.
atomic
Consider
collim ator
diameter;
now t h e
assembly).
u n i t area.
and Aa i s
product
This
gives
the w i d t h
na (a = t o t a l
of a s in g le
width
of
t h e number o f atoms per
For t h e MSU s o u r c e t h e f o l l o w i n g
conditions
exist:
a = Imm5 Aa = .012mm, T = 45%, G = 20 and I / 60 = 2 . 2 x 1 O^2
2
a t o ms / c m
f o r a r g o n at o ms .
The a t o m i c beam t h u s t h e o r e t i c a l l y
I O
O
c o n t a i n s a maximum o f 4 . 0 8 x 1 0
at oms/ cm .
The c o l l ima t i o n , C , has s i g n i f i c a n c e
reduction
o f the Doppler
C o n s i d e r a beam d e f i n e d
has.a w id th
has a w i d t h
designated
is
a]
in
.
If
the d is ta n c e
by d ^ t h e n
of
the d i r e c t i o n
predicting
of a s p e c tra l
by two c o l l i m a t i n g
the d i r e c t i o n
the r e c i p r o c a l
toward
broadening
in
s lits .
of observation
line.
The f i r s t
and t h e second
bet ween t he two s l i t s
t h e c o l l i m a t i on C = 2 d 1 / ( a ^ + a 2 ) .
t h e maximum a n g l e
of observation.
that
beam w i t h
of
C = 20 ,
I 87mk ( I
this
width
This
In the p r e s e n t source
mk = 10~2c m~^ ) .
is
is
t h e atoms make
C = 20. . The a r g o n atoms a t room t e m p e r a t u r e c o r r e s p o n d
Doppler w i d t h ^
the
reduced to
Us i ng
to a
the atomic
= 9 . 4mk.
III.
See F i g u r e s
including
an e x c i t a t i o n
electrons
The e n t i r e
region.
firs t
collimated
a sheet o f
beam d i r e c t i o n
v i e ws
into
to
by t h e s e atoms
the
lig h t
is
perpendi­
beams.
Description
Beam*I
The Beam i s
leak
produced
valve
to
The beam passes
excitation
in
a copper tube using
regulate
through
r e g i o n . ’ . The f i r s t
I Omm l o n g and I mm w i d e .
cha nne l ed c o l l i m a t o r
L a r s o n . ^^
It
This
to
is
from the e x c i t a t i o n
2)
in
that
separately.
(See F i g u r e
apertures
is
8mm.
direction
of
the monochromator.
in
the
t he
is
o f an " a i m e d " m u l t i ­
p r o d u c e d by S t a n l e y and
the wall
s lit
separating
is
8mm l o n g
t h e oven
Each chamber i s . pumped
The d i s t a n c e
The I mm w i d t h s
reaching
t he oven s l i t ,
of c o llim a tin g
chamber .
a VacTronic
amount o f gas atoms i n
aperture,
consists
sim ilar
s lit
the
two a p e r t u r e s
The second a p e r t u r e
and I mm w i d e .
region
then
emitted
and a t o m i c
Apparatus
beam.
is
by t h r e e
gun d i r e c t s
The l i g h t
by a. m o n o c h r o m a t o r w h i c h
beam a p p a r a t u s
evacuated
to the atomic
to both the e l e c t r o n
variable
atomic
An e l e c t r o n
perpendicular
The A t o m i c
PROCEDURE
A beam o f Argon atoms
t h e a r gon a t o ms .
analyzed
cular
I , 2.
t h e mo n o c h r o ma t o r i s
vacuum pumps.
excite
EXPERIMENTAL
separating
o f the s l i t s
are
The - c o p p e r t u b e ,
in
t h e two
the
including
“ 6-
THE
ATOMIC
BEAM
FIG. I
LIGHT
SOURCE
- 7-
PUMP
ATOMIC
BEAM
h _ r
MONOCHROMATOR
Electron
Gun
v A y x /v ,
%
PUMP
CROSS SECTION OF THE ATOMIC BEAM
FI G.
2
LIGHT
SOURCE
-8-
the m u l t i - c h a n n e l e d
able bellows
collim ator
so t h a t
can be moved u s i n g
t h e beam i n t e n s i t y
r e g i o n may be ma x i mi z e d b e f o r e
excitation
a spectral
s c an .
The c o n c e p t o f a m u l t i - c h a n n e l e d
collim ator
has been
in
the l i t e r a t u r e . T h e
present atomic
L a r s o n . ^^
stacking
fo il.
beam s o u r c e f o l l o w s
This m u lt i- c h a n n e le d
forty
layers
Each f o i l
photoetching.
region
ual
the
taking
discussed
size
in
an a d j u s t ­
.001
has f o r t y
inch
fo il
is
cross-sectional
Dense beams a r e p o s s i b l e
focus
The E l e c t r o n
dimensions
copper
the e x c i t a t i o n
collim ator.
ar e
. 25mmx. 0 1 2mm.
The.ratio
defines
the
The
The i n d i v i d
t h e maximum beam d e n s i t y
and s t a c k i n g
gun d e s i g n
by R o b i s c o e J ^
houses t h e e l e c t r o n
collim ator
by
is
t he
o f open ar ea t o
forty
fo ils
is
transmittance.
Gun
The e l e c t r o n
constructed
This
in
p a t h o f t h e atoms e q u a l i n g
etching
a p p r o x i m a t e l y 45%,
beryllium
base o f t h e
narrow dimension o f the c h a n n e l .
c l o s e d ar e a a f t e r
and
constructed
I 6mmx3. 5mmx. 025mm.
since
g o v e r n e d .by t h e mean f r e e
of Stanley
is
(.025mm)
in.the
r e c t a n g u l a r ' grooves f o r me d by
30mm f r o m t h e
o f an i n d i v i d u a l
the design
collim ator
They a r e ai med t o
at a point
channel
of
collim ator
for
the e x c i t a t i o n
is
based on an e l e c t r o n
See F i g u r e
gun t h u s , t h e
the e l e c t r o n
region
for
beam.
the
3.
A' pe r ma n e n t magnet
magnetic f i e l d
The s l o t t e d
atomic
beam.
gun
acts
as a
anode c o n t a i n s
See F i g u r e 3 ( b ) .
- 9-
Collimated Atomic Beam
Anode
Filament
Slit Facing Monochromator
(b.) GEOMETRY
OF ATOMIC BEAM IN THE E-GUN
Copper Support
<—i-Magnet Pole Piece
Boron Nitride
Magnet
Anode
Copper
Filament
Support
Filament
"^Filament Light
Shield
(a.)
E-GUN
ELECTRON
IN
GUN
FIG. 3
MAGNET
ASSEMBLY
- I O-
As e l e c t r o n s
leave
them t o w a r d s
t h e anode.
into
a sheet.
the f i l a m e n t ,
A s lit
monochromator f o r
The m a g n e t i c f i e l d
cut
viewing
t h e gun a s s e mb l y a r e
in
insulated
The m a g n e t i c
vacuum f e e d
fie ld
in
The anode c o n s i s t s
cathode
is
constructed
f i l a m e n t on two
connected
t o one o f
The v a r i o u s
C u r r e n t and v o l t a g e
throughs
in
the w a ll
region
them
t he
parts
of
the chamber.
I OOQ
o f a mac hi ne d c o p p e r b l o c k .
The
tungsten
is
of
connections
roughly
by s p o t w e l d i n g
. 020 i n c h
collimates
f r o m t h e magnet and each o t h e r
the e x c i t a t i o n
gauss.
accelerates
t h e c o p p e r anode f a c e s
radiation.
by a b l o c k o f b o r on n i t r i d e .
a r e made w i t h
t h e anode v o l t a g e
a .008 i n c h
support.
t h e magnet p o l e f a c e s
tungsten
A shield
to block
is
out d i r e c t
r a d i a t i o n from the heated f i l am e n t to the monochromator,.
Also,
all
parts
of
the e l e c t r o n
monochromator ar e o p t i c a l l y
The magnet i s
late ral
gun a s s e mb l y v i s i b l e
blackened w i t h
suspended on two r o l l e r
movement i n
order
to maximize l i g h t
monochromator from t h e e x c i t a t i o n
a d j u s t m e n t can be done w h i l e
the
region.
graphite.
bearings
reaching
This
s yst em r e ma i n s
vacuum by means o f a s m a l l
rack
through.
Thus t h e
o u t p u t o f the l i g h t
ma x i mi z e d
by p r o p e r a d j u s t m e n t o f
the e l e c t r o n
radient
to the
allowing
the
lateral
under a
and g e a r on a r o t a t a b l e
both
feed
s o u r c e can be
the atomi c
beam and
gun p o s i t i o n .
The g e o m e t r y o f
t h e beam and t h e e l e c t r o n
gun a l l o w
the
•
-11-
monochromat o. r t o a n a l y z e
and a t o m i c
beam m o t i o n s .
of the s p e c tra l
lig h t
This
at
90°
reduces
to both
the e l e c t r o n
the Doppler
broadening
lines.
An anode c u r r e n t
r e g u l a t o r ^ 5 is
c o n s t a n t anode c u r r e n t
experiment.
the
For
in
used t.o m a i n t a i n
the e l e c t r o n
gun t h r o u g h o u t
i n s t a n c e a t an anode v o l t a g e
c o n s t a n t anode c u r r e n t
o f any v a l u e f r o m 0 t o
of
a
the
100 v o l t s
a
15 MA can be
maintained.
Detection
System
A McPherson model
path
215 vacuum mo n o c h r o ma t o r w i t h
length
scans
the
u ltra v io le t
lines
t o be s t u d i e d .
so as t o r e s o l v e
ion
lines.
s lit
and
spectral
. 200mm f o r
s lit
widths
the e x i t
Sodi um s a l i c y l a t e
is
RCA 4523 p h o t o m u l t i p l i e r
lines
were
are
the various
kep t narrow
o f a r g o n and t h e two ■'
. 150 mm f o r
the entrance
s lit.
d e p o s i t e d on t h e p y r e x wi ndow o f t h e
tube.
of
this
in
the extreme u l t r a v i o l e t .
at
1 300 v o l t s
measur ed w i t h
and a l l o w s
The s l i t s
t h e two r e s o n a n c e
Typical
film
lines
one m e t e r
The p h o s p h o r e s c e n t p r o p e r t i e s ' ®
on t h e wi ndow e n a b l e s
the tube t o d e t e c t
The p h o t o m u l t i p l i e r
negative.
The p h o t o m u l t i p l i e r
a Keithley
601 e l e c t r o m e t e r ;
is
current
radiation
operated
is
Vacuum System
T h r e e NRC d i f f u s i o n
pumps, two o f
them f o u r
inches
in
-12-
d i a m e t e r and t h e o t h e r one t h r e e
the e n t i r e
assembly.
on t h e oven chamber .
excitation
liquid
One f o u r
inch
trap.
inch
in
a Granville
t h e oven c hamber ,
ma to,r and 4 x 1 0 " ^ T o r r
in
Typical
Cryosorb
pumped by t h e
sorbent ba ffel
base p r e s s u r e s
3x10™6 T o r r
the e x c i t a t i o n
a trap
the
P hillips
pump and uses a NRC m o l e c u l a r
zeo lite.
without
pump e v a c u a t e s
The m o n o c h r o m a t o r i s
t y p e 0317-4 charged w i t h
2x10"6 Torr
a r e used t o e v a c u a t e
pump o p e r a t e s
chamber and u t i l i z e s
nitrogen
other four
The s m a l l
inches,
in
chamber .
ar e
t h e mo n o c h r o ­
IV;
MEASUREMENTS AND RESULTS
In itia l
Obtaining
lines
of
t ra ce s howi ng t h e e x p e c t e d r e s o n a n c e
a spectral
o f Ar gon was o f p r i m e
the e a r l y
spectral
Experiments
importance.
scans
using
Figure
4 shows one
t h e ar gon a t o m i c
beam.
two l i n e s
a t 9 1 9 . 7 8 A and 93 2 . 0 5 A a r e t h e e m i s s i o n
the f i r s t
excited
state
of singly
ionized
argon.
ionization
energies
potential
(A r.II)
(3s^3p^)
excited
of
correspond
excitation
respectively.
lines
state
for
used c a u s i n g
chamber t o
are
( 3 s 23 p 54s)
to
(A r.I)
energies
spectral
self-absorption
A spectral
of
of
scan.
intensity
and oxygen l i n e s
this
in
in
the e x c i t a t i o n
5.
Therefore
occurs.
as t h e m o l e c u l a r
Figure
are noted
the ion
stems f r o m t h e o p e r a t i n g
the resonance l i n e s
air
of
3x10"^ T o r r ) .
t h e e m i s s i o n s p e c t r u m seen i n
region.
11. 82 7 eV and 11 . 6 2 3 eV
A v e r y dense beam was
(on t h e o r d e r o f
scan u s i n g
from
These w a v e l e n g t h s
t h e b a c k g r o u n d Ar gon p r e s s u r e
be h i g h
lines
the ground s t a t e
the resonance l i n e s
this
threshold
The
the resonance
The a p p a r e n t l y g r e a t e r
compared t o
conditions
lines
t h e a r g o n at om.
to
( 3 s 23 p 5 )
o f an ar gon atom c o r r e s p o n d t o
1 0 4 8 . 2 2 K and 1 0 6 6 . 6 6 A ^
from
These w a v e l e n g t h s pi us t h e
o f 2 9 . 2 3 8 eV and 2 9 . 0 5 9 eV r e s p e c t i v e l y .
the f i r s t
lines
t h e ground state
(3s3p6 ) to
The
Some o f
beam p r o d u c e d
the
nitrogen
e x t r e me vacuum u l t r a v i o l e t
O
ANODE VOLTAGE IOOV
ANODE CURRENT IOmA
CHAMBER PRESSURE 3 X I 0 ~ J TORR
I
I
900
IOOO
WAVELENGTH
SPECTRAL
I IOO
(A)
SCAN WITH ARGON
FIG. 4
BEAM
ANODE VOLTAGE
200 V
ANODE CURRENT I OmA
CHAMBER PRESSURE 1 . 3 X 1 0 “ °
TORR
O
O
CJ
NI
1742
H
Z
I OOO
12 0 0
1400
1600
WAVELENGTH ( A )
SPECTRAL SCAN WITH
AIR
FIG. 5
MOLECULAR
BEAM
-16-
Secondary E l e c t r o n
The l i n e a r i t y
demonstrated f o r
of quadratic
electron
to
of current with
t h e two i o n
diverge
in
some e l e c t r o n s
traveling
the e x c i t a t i o n
The r e l a t i v e
for
optical
as a f u n c t i o n
density
line
energy f o r
to
functions
excitation
found
show, t h e
in
the
of
o f secondary
starts
being c o l l i m a t e d
and
(See F i g u r e 3 ) . *
Functions
o f the e l e c t r o n
the th re s h o ld
The l a c k
The l i n e a r i t y
region.
Figure
and c o n s t a n t e l e c t r o n
is
A t t h e s e anode c u r r e n t s
excitation
a r e shown i n
a gi ven, s p e c t r a l
line
beam.
t h e anode w i t h o u t
E xcitation
6.
the p o s s i b i l i t y
o f the atomic
reach
inte nsity
See F i g u r e
t h e 12 - 1 4 ma r e g i o n .
through
Ar gon 11 l i n e s
lig h t
lines.
behavior elim in a te s
excitation
Effect
functions
7.
t h e two
The e x c i t a t i o n
re la tive
in te n sity
energy f o r
current.^
lines.
of
functions
of that
c o n s t a n t atom
The p l o t
begi ns
at
A t p r e s e n t no r e f e r e n c e s
t h e s e Ar gon I I
lines
have been
the l i t e r a t u r e .
P r e s s u r e Dependence o f t h e Ar gon I Resonance L i n e s
An u n e x p e c t e d p r e s s u r e dependence o f t h e A r
lines
atomic
appeared'in
beam l i g h t
was d u p l i c a t e d . a
testing
the o p e r a t i o n a l
s o u r c e . ' See F i g u r e s
number o f t i m e s .
,
This
:
,
I
a b ility
8-10.
effect
This
is
resonance
o f the
behavior
not
-17-
ANODE VOLTAGE - 3 0 0 V
5
CHAMBER PRESSURE
3 X 1 0 ” TORR
919.78 A
(ARBITRARY
U N IT S )
40-
3 0 -•
INTENSITY
932.05 A
CURRENT
INTENSITY VS. CURRENT
FIG. 6
(MA)
FOR
ARGON H
ANODE
CURRENT
CHAMBER
o - 920 A
5 mA
PRESSURE
3 X 1 0 “ 5 TORR
x-932 A
INTENSITY
(ARBITRARY
UNITS)
2 Of
ELECTRON
EXCITATION
FUNCTIONS
ENERGY IN
OF
920 A
eV
AND
FIG. 7
ABOVE
THRESHOLD
932 A
LINES
OF
ARGON H
(ARBITRARY UNITS)
30-
Anode
Voltage
Anode
Current
100 V
IO mA
25 -
2 0 ..
15. .
IN TE NSIT Y
I
1*0
I
O
P R ESS URE
INTENSITY
VS.
PRESSURE
(X IOFOR
FIG. 8
TORR)
1048.22
A
OF ARGON I
UNITS)
IOO V
I O mA
-
(ARBITRARY
Anode Voltage
Anode Current
20
INTENSITY
-
6
INTENSITY
PRESSURE (X 10™ TORR) 0
VS. PRESSURE
FOR
1066.66 A
FIG. 9
OF
ARGON
I
Anode Voltage
Anode Current
IOO V
IO mA
2 .5 -TINTENSITY
INTE NS IT Y
OF
OF
1048 .22 &
1066 .66 A
IZ-
RATIO
RATIO =
0.5 -
PRESSURE
RATIO
OF
( X I O - 6 TORR)
INTENSITIES
VS.
FIG. IO
PRESSURE
FOR
ARGON
I
-22-
com pletely understood
although
ed.
the da ta ,
Before analyzing
had t o be c o r r e c t e d . ^
The p r e s s u r e
sim ila ritie s .
the
The i n t e n s i t i e s
before
increasing
is
set fo r th
of
this
the
radiation
to
the quenching
Also
of
of
his
the
20
Zemansky
radiation
theoretical
cients.
This
Absorption
when t h e b a c k ­
type o f s c a tt e r in g
appl i e d M i l n e ' s
by an i n f i n i t e
results
the d i f f u s i o n
to
slab
the r a t i o
of
stems f r o m t h e d i f f e r i n g
resulting
The a b s o r p t i o n
in
the
t h e p r e s e n t da t a
the Ar
I
process
inte nsities
See F i g .
o scilla to r
in
lines.
10.
un d e r
A partial
strengths
d iffe re n t absorption
process ga ins
theory
of absorbing
importance o f the s c a t t e r in g
in te re s t,is
depends
background gas.
concerning
pI
t h e p r e s s u r e dependences' o f
two t r a n s i t i o n s
This
t h e r e may o c c u r a
t h e same b a c k g r o u n d " p r e s s u r e c h a n g e s .
explanation
mi ni mum p o i n t
the absorbing
absorption
a gas.
may show t h e r e l a t i v e
interpreting
of
as
maximum o c c u r s .
The amount o f a b s o r p t i o n
theory o f"M iln e
through
rapidly
pressure.
radiation
the re so na nt photons.
in
Adapting
a re la tive
to a r e l a t i v e
decrease in
and t h i c k n e s s
of
gas*
off
increases.
However, along w i t h
re-emission
until
showed some
a combination o f e f f e c t s .
causes an e x p o n e n t i a l
readings
climb q u ite
somewhat I i n e a r l y w i t h
be h a v io r suggests
on t h e d e n s i t y
the curves
increased
then t r a i l
ground p r e s s u r e
t h e ar gon p r e s s u r e
b e h a v i o r o f t h e two l i n e s
is
are s u g g e s t ­
^
Fo r i n s t a n c e ,
beam d e n s i t y
some p o s s i b i l i t i e s
for
co e ffi­
i m p o r t a n c e a g a i n as t h e
-23-
background pres sur es
t h e two l i n e s
respectively.
thus
8,
~4.
9)
their
22
It
The r a t i o
with
o scilla to r
. 059 f o r
the
strengths.
data f o r
the o s c i l l a t o r
the s c a t t e r e d
to
t he
observation
inverse
t he
radiation
to
for
about
coe fficient
They n o t e d
e me r g i n g
for
that
at
ratio
of
•
1067 A i t
the o s c i l l a t o r
is
of Mitchell
proportional
l ow p r e s s u r e s
from a t h i c k n e s s
the a b s o r p t i o n
is
(Figures
re la tive
by t h e d i s c u s s i o n
the a b s o r p t i o n
s t r e n g t h ..
proportional
t h e two l i n e s
For i n s t a n c e ,
m i g h t be s u b s t a n t i a t e d
since
strengths
a b o u t 3x10 ^ T o r r w h i l e
This
strengths
1 048 K and 1 067. A
pressure according
1048 A i s
and Zemansky
gas i s
The o s c i l l a t o r
of these o s c i l l a t o r
that
a t 12 x 1 0~6 T o r r .
strengths
to
. 228 and
ap p e a r s
scales
maximum f o r
occurs
are
increase.
coe fficient.
of absorbing
V.
The. a t o m i c
beam l i g h t
produced a to mi c
More i m p o r t a n t
emission
p e r ha ps
experiments w ith
contained
in
s o u r c e has f u n c t i o n e d w e l l
lines
than the
in
results
source.
obtained w ith
for
For i n s t a n c e ,
p r o v i d e an e f f e c t i v e
atomic
behavior.
m aterial
for
future
in itia l
future
use
most o f t h e
beam f o r
The p r e s s u r e dependences o f r e s o n a n c e l i n e s
interesting
and has
t h e vacuum u l t r a v i o l e t .
argon are the p o s s i b i l i t i e s
such a l i g h t
r a r e gases c o u l d
work.
CONCLUSION
s t u d y due t o t h e i r
resonance
also
offer
unexplained
APPENDIX
APPENDIX
The d e r i v a t i o n
Stanley's
paper.
derivation
9
o f t h e maximum beam d e n s i t y
The f o l l w o i n g
discussion
b u t uses t h e g e o me t r y o f
called
aperture
into
t h e o v e n.
The beam passes
a r e g i o n o f much l o w e r
The number d e n s i t y ,
in
in
his
source.
a high pressure
through
pressure.
n , at a p o in t c is
given
parallels
t h e MSU l i g h t
Con sid er the atomic-beam to o r i g i n a t e
region
is
t h e oven
See F i g u r e
the d e s i r e d
11.
quantity.
( al bi )
n =
(I)
1 Aird2 2
Corresponding
dimensions
n-, i s
1
solid
free
to
Figure
11,
o f t h e r e c t a n g u l a r oven a p e r t u r e .
t h e number d e n s i t y
fo r molecular e ffu s io n
atomic
inside
L , o f t h e atoms
assumed m o l e c u l a r
diameter,
The q u a n t i t y
t h e oven and a ~*. p i s t he
dg
by t he a p e r t u r e .
Of c o u r s e t h e mean
angle subtended
path,
a-j and b^ a r e t h e n a r r o w and wi d e
in
t h e oven must be l a r g e r
to occur
effusion).
(Equation
(I)
Now c o n s i d e r
has a l r e a d y
6 as t h e e f f e c t i v e
then
I
(
VrZrc 6 2n
I
°r.
2)
'
D e f i n e a c o n s t a n t a = A/Zre § .
L-Slb
t h a n a-j
From ( 2 )
"I
we have
(3)
F o r a maximum n-j we s e t L = a ^ so
_ 4 tt
(4)
-27-
Z
ATOMS
__OVEN
APERTURE
CHAMBER
APERTURE
ELECTRON
X
COLLIMATION
OF AN ATOMIC BEAM
FIG. Il
BEAM
-28-
Subs t i t u t i ng i n t o
n =
(I),
t h e beam d e n s i t y
becomes
bI
(5)
ad,
The l o n g d i m e n s i o n
Thus we a r r i v e
..
'
o f the s l i t ,
b1 , i s
approxi matel y dg/2.
at
I
2ad,
(
A second c o l l i m a t i n g
is
placed
aperture
bet ween p o i n t
allows
a p e r t u r e w i t h di mensi ons
c and t h e oven a p e r t u r e .
o n l y a s ma l l
to reach t he e x c i t a t i o n
number o f
region.
6)
a 2 and bp
Thi s
second
t h e at oms f r o m t h e oven
The c o l l i m a t i o n
of
t he beam
is
1I
C "
(7)
aI +a2
I n t h e p r e s e n t s o u r c e a ^ = a 2=a and d-j =d2/ 3 so
d2
C = Sa"
Comb i ni ng
(8)
'
‘
.
(
o r ^ 2 = 3aC
and ( 6 )
we have
I
■ 6oCa
Thus, t h e number d e n s i t y
na
6oC
8)
(9a)
pe r u n i t
ar ea
is
(9b)
-29-
If
a multi-channeled
replaces
t h e oven a p e r t u r e we f i n d
n-j
Wi t h
in
with
channel
w i d t h Aa
that
= 4n(oAa)
(11)
the n u l t i - c hannel ed
the o v e r a l l
collimator
d i m e n s i o n s a^xb^
transmittance T is
Usi ng I
collimator
and ( 1 1 )
the r a t i o
we a r r i v e
transmits
na = 6 C 5 H
t h e ar ea
at oms .
included
. The
o f open ar ea t o c l o s e d a r e a .
at
the f i n a l
" = Ic k s
The number d e n s i t y
not a l l
results
for
n.
0 2 »)
per u n i t
ar ea
is
02b)
LITERATURE CITED
j
LITERATURE CITED
1.
W. H. Bassey and 0.
2.
J . E. Mack and E. C. B a r k o f s k y ,
82 ( 1 942) .
Rev.
3.
J . G. Ki ng and J. E. Z a c h a r i a s ,
Phys. ' 8 , I (1956).
Adv. . E l e c t .
4.
R. W. S t a n l e y ,
5JI, 500 ( 1 9 6 0 ) .
5.
V.
6.
I.
• G. R.
J . Opt .
Odintsov,
Hanes,
C. Si mp s o n ,
Opt .
S o c . Am.
Chem. Re v . 30,
239 ( 1 9 4 2 )
Mod. P h y s . 14,
.;
—
Electron
S p e c t r y . 1_0, 202 (1 961 ) .
J . A p p l . P h y s . 31,
2171
(1960).
7.
K . K l e i n p o p p e n , H . K r u g e r , and R. U l m e r , Phys . L e t t e r s
78 (1 962) .
8.
John 0.
9.
R. W.
Stoner,
J . Opt S o c . Am.
H , 1377 ( 1 9 6 4 ) .
Stanley,
J . Opt . S o c . Am.
5j6 , 350 ( 1 9 6 6 ) .
J . Opt .
2,
10.
H a r o l d P . L a r s o n and R o b e r t W. S t a n l e y ,
57, 1439 ( 1 9 6 7 ) .
S o c . Am.
11.
Raymond L . Kel I y „ A t o mi c E mi s s i o n L i n e s B e l o w ' 2000
A n g s t r o m s - - H y d r o g e n Thr ough A r g o n , Naval Resear ch Lab
( 1 968) .
12.
E. T .
and
13.
E. U. Condon and G. H. S h o r t ! e y , The T h e o r y o f At o mi c
S p e c t r a , p. 139; Cambr i dge U n i v l P r e s s , New Yor k ( 1 9 6 4 )
14.
R. T.
15.
The anode c u r r e n t r e g u l a t o r was d e s i g n e d
Fr ed B I a n k e n b e r g .
16.
E. C'. B r u n e r ,
17.
C. Smi t , H. G. M. Hei deman and J . A.
245 ( 1 9 6 3 ) .
Smi t , P h y s i c a
18.
Saul Dushman, S c i e n t i f i c F o u n d a t i o n s
2nd e d . , John W i l e y and Sons I n c . ,
o f Vacuum T e c h n i q u e ,
New Y o r k ( 1 9 6 2 ) .
V e r k h o v t s e v a , V. P. S t r e l
N i k o v , V. N. S o k o l o v ,
B . N. Popov., Z h . P r i k l . S p e c t r o s k . 7_; 859 ( 1 967 ) .
Robiscoe,
P h y s . Rev. ]_38, A22 ( 1 9 6 5 ) .
Jr.,
J . Op t ,
and b u i l t
by
S o c . Am. j[9 , 204 ( 1 9 6 9 ) .
29,
-32-
19.
L . R i d d l e f o r c l 5 J.
20.
E . A.
21.
M. W'. Ze man s k y 5 Phys . R e v .
3_6, 91 9 ( 1 9 3 0 ) .
22.
G. M. L a w r e n c e , P h y s . Rev.
1 7 5 , 40 ( I 968)
23.
A. C. G. M i t c h e l l and M. W.Ze man s k y 5 Resonance R a d i a t i o n
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Sci . I n s t .
J . Lon. Math.
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M 0Ii I a n 4 ST4TE UNIVERSITY LIBRARIES
1762 10013892
N37S5
G745
cop. 2
Govertsen, Glenn Alden
A vacuum ultraviolet
atomic beam light source
NAMK ANP ^ODwgaa
m
i g
Qrl^1S
C.JD
p
.