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Science Forum Index » Physics - Research Forum » cause of light bursts in sonoluminescence
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| verdigris |
 Posted: Sun Mar 04, 2007 4:45 am |
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When noble gases are "injected" into bubbles in the phenomenon of
sonoluminescence, the light bursts intensify.It is possible that
the noble gas is being heated and made to glow in the walls of the
bubble or inside the bubble itself.But how is the heating occurring -
is it electrical heating from charges passing through the noble gas or
frictional heating from migration of ions?
Assuming that there is a potential difference across the bubble
surface caused by OH - and H + ions (in the case of water for
example) , OH - ions on one hemisphere and H + ions on the other, and
knowing that a bubble is typically 10 ^ - 6 metres across and the
bursts last for about 10 ^ -10 - 10 ^ -11 seconds, we have to conclude
that the hydroxyl ions and protons move towards one another across the
surface of the bubble (to form water molecules) at about 10 ^ 4 - 10 ^
5 m / s (unless we are dealing with slow moving electrons and a net
drift velocity here)These ions typically move in water at only 10 ^ 2
- 10 ^ 3 m/s.
Could they be moving at higher speeds than normal because of the
concentration of energy from sound waves? Or are we dealing with noble
gas heating caused by slow moving electrons? Can anyone offer some
advice on this? |
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| verdigris |
| Posted: Sun Mar 04, 2007 9:06 am |
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Guest
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On 4 Mar, 14:45, verdigris <waltercr...@aol.com> wrote:
Quote: Could they be moving at higher speeds than normal because of the
concentration of energy from sound waves?
Verdigris:
A simple calculation using the coulomb interaction Force = kq1q2/ r ^
2 and Newton's Law, acceleration = force/mass, in a 10 ^ - 10 to 10 ^
- 12 second time frame (how long a bubble and the light bursts lasts
for) and the assumptions that the surface of the hemispheres of the
bubbles are fully charged with OH - and H + ions, and that there is a
near vacuum inside the bubbles and little interaction via the electric
force between the charged ions and surrounding medium,reveals that the
bubble walls can come together at a speed of 10 ^ 5 - 10 ^ 7 m/s !!
This would undoubtedly heat the noble gases.
On Wikipedia it says:
Writing in Nature, chemists David J. Flannigan and Kenneth S. Suslick
study argon bubbles in sulfuric acid and show that ionized oxygen ,
sulfur monoxide, and atomic argon populating high-energy excited
states are present, implying that the bubble has a hot plasma core. |
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| Uncle Al |
| Posted: Tue Mar 06, 2007 3:48 am |
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Guest
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verdigris wrote:
Quote:
When noble gases are "injected" into bubbles in the phenomenon of
sonoluminescence, the light bursts intensify.It is possible that
the noble gas is being heated and made to glow in the walls of the
bubble or inside the bubble itself.But how is the heating occurring -
is it electrical heating from charges passing through the noble gas or
frictional heating from migration of ions?
Assuming that there is a potential difference across the bubble
surface caused by OH - and H + ions (in the case of water for
example) , OH - ions on one hemisphere and H + ions on the other, and
knowing that a bubble is typically 10 ^ - 6 metres across and the
bursts last for about 10 ^ -10 - 10 ^ -11 seconds, we have to conclude
that the hydroxyl ions and protons move towards one another across the
surface of the bubble (to form water molecules) at about 10 ^ 4 - 10 ^
5 m / s (unless we are dealing with slow moving electrons and a net
drift velocity here)These ions typically move in water at only 10 ^ 2
- 10 ^ 3 m/s.
Could they be moving at higher speeds than normal because of the
concentration of energy from sound waves? Or are we dealing with noble
gas heating caused by slow moving electrons? Can anyone offer some
advice on this?
Look up Ken Suslick's work including blackbody and species band
spectra of the bubbles, His experimtens in concentrated sulfuric acid
with argon are particulary nice. Google.
Heating is pseudoadiabatic compression. A good model is a WWII depth
charge. The thing goes down a few hundred feet depth and detonates.
You see a surface swell. The vapor bubble cools, implodes, then
rebounds. THAT is the huge surface burst.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2 |
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| verdigris |
| Posted: Tue Mar 06, 2007 1:58 pm |
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On 6 Mar, 13:48, Uncle Al <Uncle...@hate.spam.net> wrote:
Quote: verdigris wrote:
Heating is pseudoadiabatic compression. A good model is a WWII depth
charge. The thing goes down a few hundred feet depth and detonates.
You see a surface swell. The vapor bubble cools, implodes, then
rebounds. THAT is the huge surface burst.
Verdigris:
The bursts of light from the bubbles are too short to be explained by
atomic transitions from heating
http://66.102.9.104/search?q=cache:rzh2XeSH0ncJ:focus.hut.fi/annrep/1996/node33.html+sonoluminescence&hl=en&ct=clnk&cd=4&gl=uk&ie=UTF-8
There is also a phenomenon in nature called Shrimpoluminescence in
which the pistol shrimp snaps its claw in water and produces light
from bubbles.
http://en.wikipedia.org/wiki/Shrimpoluminescence#Shrimpoluminescence
The light emitted is less intense than from laboratory type
sonoluminescence
and that is likely to be because water vapour in the bubble resists
the collapse of the bubble.This is why Ken Suslick used sulphuric acid
in the laboratory - to minimise vapour pressure in the bubble and
maximise the speed of bubble collapsing.
When sonoluminescence sets in, the radius of the bubble suddenly
decreases for a moment before rising again.The charged ions I suggest
may actually be just under the bubble surface and as they move inwards
they may be briefly pulling the bubble wall with them. Also note that
bubbles collapse in about 10 ^ - 6 seconds.Light flashes last 10 ^ -12
seconds.Charged ions accelerating towards one another would explain
this discrepancy in times.Non-polar molecules are not great at
producing sonoluminescence on their own and sometimes even in mixtures
e.g an N2 - O2 mix gives weak light emission.Noble gases at about 1%
of the composition of the total mix seem to optimise light
emission.This is possibly because noble gases being unreactive and
electronically unpolar may be present in the bubble wall and not
pulling the charged ions back so strongly as the surrounding medium
does when light emission begins.The charged ions will thus accelerate
more. |
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| verdigris |
| Posted: Tue Mar 06, 2007 1:58 pm |
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Guest
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On 6 Mar, 13:48, Uncle Al <Uncle...@hate.spam.net> wrote:
Quote: verdigris wrote:
Heating is pseudoadiabatic compression. A good model is a WWII depth
charge. The thing goes down a few hundred feet depth and detonates.
You see a surface swell. The vapor bubble cools, implodes, then
rebounds. THAT is the huge surface burst.
Verdigris:
I'm still suspicious that the bubble surface is electrically charged
because
if it is assumed that there is about 10 ^ -10 metres - a typical
atomic distance -between charges and the bubble surface is charged at
every location (no electrically neutral species) the maximum speed an
individual hydroxyl or hydrogen ion can reach is,using the
calculation of the type I mentioned in my previous post,about 10 ^ 7 -
10 ^ 8 m/s.This is what we would expect given what relativity theory
says about the maximum speed of a rest mass. |
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| verdigris |
| Posted: Sun Mar 11, 2007 10:19 am |
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Guest
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On 6 Mar, 23:58, verdigris <waltercr...@aol.com> wrote:
Quote: The bursts of light from the bubbles are too short to be explained by
atomic transitions from heating
Verdigris:
I found reading around that noble gases increase the intensity of
light bursts (noble gases let more light energy escape because they
don't have chemical bonds that can absorb energy).However, helium
increases the intensity more than xenon which is much heavier The
lighter helium will be more volatile and there will be more of it in
the bubble, exerting a greater vapour pressure in the bubble.As the
bubble contracts the helium will be compressed and raise the bubble
temperature more than xenon can (it is known that helium causes the
bubble to emit shorter wavelength light than xenon -10 ^ - 8 m
compared to 10 ^ -7 m).But why are the light bursts much shorter in
duration than atomic transitions? I think the answer is this:according
to Ken Suslick at
http://66.102.9.104/search?q=cache:6Q_6nktVpN8J:www.bioedonline.org/news/news.cfm%3Fart%3D1626+ken+suslick+argon&hl=en&ct=clnk&cd=1&gl=uk&ie=UTF-8
the bubble temperature can reach 15000K .There could be a thin layer
of positive and negative charges on the bubble surface at this
temperature, that is reflecting light back into the bubble.The bubble
takes 10 ^ - 6 seconds to collapse - plenty of time for atomic
transitions of electrons to take place on a timescale of 10 ^ - 8
seconds per transition.When the bubble walls get close together the
separated charges on the surface of the bubble might recombine in
about 10 ^ -11 seconds, letting out the light.
There is an analagous process that happens in semiconductors where
holes and electrons that are in close proximity recombine in about 10
^ -11 seconds.However, for the bubble,the recombination of charges is
probably caused by the shockwave sent out as the walls of the bubble
exert a force on one another. |
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