Hello,

I have a question about excimer physics I'm hoping someone could
answer:

>From what I read, pulsed high pressure (several hundred torr) DBD
(dielectric barrier discharge) driven pure xenon lamps produce
a high power (tens of watts average) high efficiency (40 to 60%), 172
nm output of high spectral purity.

In light of this, would it be possible to use xenon as the active
material (Xe or maybe an Xe/He mixture) in a pure xenon excimer laser
operating at 172 nm? And if not, why not?

Regards,
Joe

From:	jpsmith123 at yahoo.com
Subject:	Re: Any excimer knowledgeable people here?
Date:	23 Jan 2005 00:10:35 -0800

Hello,

Thanks for your reply and the informative link.

I'm not sure I understand the phrase "[e]xcited state absorption";
isn't that a contradiction in terms? In other words, wouldn't an
excited xenon dimer, by definition, be expected to emit rather than
absorb a photon of 172 nm wavelength?

Regards,
Joe

From:	news
Subject:	Re: Any excimer knowledgeable people here?
Date:	Sun, 23 Jan 2005 05:54:36 -0600

In a classic excimer, pumping occurs when you make the molecule (i.e. XeF),
energy is released (either by stimulated emission or spontaneous emission)
when this molecule comes apart.

Absorbtion - taking in something, your paper towel ABSORBS
Absorption - expelling something, absorption spectrum = the colors a noble
gas emits when jazzed with high voltage.

One little letter makes a huge difference

wrote in message
news:1106464009.253934.222110@z14g2000cwz.googlegroups.com...
> Hello,
>
> Thanks for your reply and the informative link.
>
> I'm not sure I understand the phrase "[e]xcited state absorption";
> isn't that a contradiction in terms? In other words, wouldn't an
> excited xenon dimer, by definition, be expected to emit rather than
> absorb a photon of 172 nm wavelength?
>
> Regards,
> Joe
>

From:	Joshua Halpern
Subject:	Re: Any excimer knowledgeable people here?
Date:	Sun, 23 Jan 2005 18:40:36 GMT

news wrote:
> In a classic excimer, pumping occurs when you make the molecule (i.e. XeF),
> energy is released (either by stimulated emission or spontaneous emission)
> when this molecule comes apart.
>
> Absorbtion - taking in something, your paper towel ABSORBS
> Absorption - expelling something, absorption spectrum = the colors a noble
> gas emits when jazzed with high voltage.

Nuuh uh. Absorption is what you get when something absorbs a photon.
Emission is what you get when something emits a photon.

An absorption spectrum is what you get when you measure the amount of
light transmitted through a system as a function of wavelength. If you
take the log of the initial intensity/transmitted intensity and plot
that vs. the wavelength you get the absorption spectrum.

josh halpern
> One little letter makes a huge difference
>
>
> wrote in message
> news:1106464009.253934.222110@z14g2000cwz.googlegroups.com...
>
>>Hello,
>>
>>Thanks for your reply and the informative link.
>>
>>I'm not sure I understand the phrase "[e]xcited state absorption";
>>isn't that a contradiction in terms? In other words, wouldn't an
>>excited xenon dimer, by definition, be expected to emit rather than
>>absorb a photon of 172 nm wavelength?
>>
>>Regards,
>>Joe
>>
>
>
>

From:	Gerard Harbach
Subject:	Re: Any excimer knowledgeable people here?
Date:	Mon, 24 Jan 2005 09:04:55 +0100

Well I am neither a native english speaker nor an excimer expert, but my
understanding was that 'to absorb' is the verb and absorption is the noun.

"Joshua Halpern" wrote in message
news:EcSId.18504$Os6.4722@trnddc08...
> news wrote:
> > In a classic excimer, pumping occurs when you make the molecule (i.e.
XeF),
> > energy is released (either by stimulated emission or spontaneous
emission)
> > when this molecule comes apart.
> >
> > Absorbtion - taking in something, your paper towel ABSORBS
> > Absorption - expelling something, absorption spectrum = the colors a
noble
> > gas emits when jazzed with high voltage.
>
> Nuuh uh. Absorption is what you get when something absorbs a photon.
> Emission is what you get when something emits a photon.
>
> An absorption spectrum is what you get when you measure the amount of
> light transmitted through a system as a function of wavelength. If you
> take the log of the initial intensity/transmitted intensity and plot
> that vs. the wavelength you get the absorption spectrum.
>
> josh halpern
> > One little letter makes a huge difference
> >
> >
> > wrote in message
> > news:1106464009.253934.222110@z14g2000cwz.googlegroups.com...
> >
> >>Hello,
> >>
> >>Thanks for your reply and the informative link.
> >>
> >>I'm not sure I understand the phrase "[e]xcited state absorption";
> >>isn't that a contradiction in terms? In other words, wouldn't an
> >>excited xenon dimer, by definition, be expected to emit rather than
> >>absorb a photon of 172 nm wavelength?
> >>
> >>Regards,
> >>Joe
> >>
> >
> >
> >

From:	AES
Subject:	Re: Any excimer knowledgeable people here?
Date:	Sun, 23 Jan 2005 09:18:51 -0800

In article <1106464009.253934.222110@z14g2000cwz.googlegroups.com>,
jpsmith123@yahoo.com wrote:

>
> I'm not sure I understand the phrase "[e]xcited state absorption";
> isn't that a contradiction in terms? In other words, wouldn't an
> excited xenon dimer, by definition, be expected to emit rather than
> absorb a photon of 172 nm wavelength?
>

Suppose laser action takes place on a transition between an upper laser
level, call it E3, with population (number of atoms) N3, and a lower
laser level, call it E2, with population N2. Laser gain is then
proportional to N3 - N2.

Suppose there is, purely accidentally, a _higher lying_ energy level E4
with the same energy gap to E3 as E3 has to E2 (and hence the same
transition frequency), and not much population because it's
higher-lying. Every atom pumped into E3 now gives gain proportional to
N3 - N2 --- and so-called "excited state absorption" or loss
proportional to N3 - N4. Not good.

(The so-called oscillator strengths of these transitions also enter into
the ratio of gain to loss.)

Can also have situations where some upper level E4 that gets pumped
along with E3 has an excited-state absorption up to a higher level E5.
Excimers have substantially broader lines than many other laser
materials, so accidental overlaps of one type or the other are more
common.

From:	Skywise
Subject:	Re: Any excimer knowledgeable people here?
Date:	Sat, 22 Jan 2005 20:41:48 -0000

jpsmith123@yahoo.com wrote in news:1106385766.165801.159070
@z14g2000cwz.googlegroups.com:

> Hello,
>
> I have a question about excimer physics I'm hoping someone could
> answer:
>
>>From what I read, pulsed high pressure (several hundred torr) DBD
> (dielectric barrier discharge) driven pure xenon lamps produce
> a high power (tens of watts average) high efficiency (40 to 60%), 172
> nm output of high spectral purity.
>
> In light of this, would it be possible to use xenon as the active
> material (Xe or maybe an Xe/He mixture) in a pure xenon excimer laser
> operating at 172 nm? And if not, why not?
>
> Regards,
> Joe

According to the Handbook of Lasers, the list for xenon ion
lasers is from about 223nm up to 1.09u, on well over a
hundred different lines. Neutral xenon is also listed but
the ranges from 823nm and goes out to 75.5 microns.

There are listings for diatomic Xe (Xe2) at 170nm to 176nm.

Further scanning also found reference to solid state excimer lasers,

"Using matrix isolation techniques, it is possible to grow large,
doped, rare-gas crystals. By introducing xenon and fluoride, XeF
molecules can thus be formed by photodissociation of F2 in
Xe-F2-Ar crystals. Optically pumped solid-state excimer laser
action has been reported for XeF in Ar and Ne crystals."

Unfortunately these are all cryogenic, 20 kelvin and below, and
are pumped in the UV with standard excimer lasers.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy

Home of the Seismic FAQ
http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html

Sed quis custodiet ipsos Custodes?

From:	Joshua Halpern
Subject:	Re: Any excimer knowledgeable people here?
Date:	Sat, 22 Jan 2005 20:06:02 GMT

jpsmith123@yahoo.com wrote:
> Hello,
>
> I have a question about excimer physics I'm hoping someone could
> answer:
>
>>From what I read, pulsed high pressure (several hundred torr) DBD
> (dielectric barrier discharge) driven pure xenon lamps produce
> a high power (tens of watts average) high efficiency (40 to 60%), 172
> nm output of high spectral purity.
>
> In light of this, would it be possible to use xenon as the active
> material (Xe or maybe an Xe/He mixture) in a pure xenon excimer laser
> operating at 172 nm? And if not, why not?
>
Xe lasers at 172 nm were demonstrated early on (in the 70s).
The ones I know were pumped by small electron accelerators like
Febatrons for example Applied Physics Letters -- November 1, 1974 --
Volume 25, Issue 9, pp. 498-500.

There appears to be more interest in Xe2 excimer lamps at this point

josh halpern

From:	matt wilson
Subject:	Re: Any excimer knowledgeable people here?
Date:	Sat, 22 Jan 2005 12:35:07 GMT

I'm no expert, I don't even know the exact method by which the medium
operates, but I DO know that most of the shorter wavelength mixes use
Flourine, which is extremely reactive. The shortest 'system' I know of uses
ArF at 192nm. AFAIK, there is a useable XeF line, but it is somewhat longer.
Maybe you could find a way to get a crystal of XeF6 to lase?

wrote in message
news:1106385766.165801.159070@z14g2000cwz.googlegroups.com...
Hello,

I have a question about excimer physics I'm hoping someone could
answer:

>From what I read, pulsed high pressure (several hundred torr) DBD
(dielectric barrier discharge) driven pure xenon lamps produce
a high power (tens of watts average) high efficiency (40 to 60%), 172
nm output of high spectral purity.

In light of this, would it be possible to use xenon as the active
material (Xe or maybe an Xe/He mixture) in a pure xenon excimer laser
operating at 172 nm? And if not, why not?

Regards,
Joe

From:	jpsmith123 at yahoo.com
Subject:	Re: Any excimer knowledgeable people here?
Date:	22 Jan 2005 18:24:03 -0800

Hello Josh,

Thanks for your reply. I haven't yet gotten the paper you referenced,
but it now appears that a pure xenon excimer laser is at least a
theoretical possibility.

In light of the fact that pure xenon is not corrosive (and this would
seem to be a big advantage over excimer mixtures containing halogens),
I'm thinking there must have been some serious drawback or
technological obstacle that prevented it from going anywhere.

Regards,
Joe

Joshua Halpern wrote:
> jpsmith123@yahoo.com wrote:
> > Hello,
> >
> > I have a question about excimer physics I'm hoping someone could
> > answer:
> >
> >>From what I read, pulsed high pressure (several hundred torr) DBD
> > (dielectric barrier discharge) driven pure xenon lamps produce
> > a high power (tens of watts average) high efficiency (40 to 60%),
172
> > nm output of high spectral purity.
> >
> > In light of this, would it be possible to use xenon as the active
> > material (Xe or maybe an Xe/He mixture) in a pure xenon excimer
laser
> > operating at 172 nm? And if not, why not?
> >
> Xe lasers at 172 nm were demonstrated early on (in the 70s).
> The ones I know were pumped by small electron accelerators like
> Febatrons for example Applied Physics Letters -- November 1, 1974 --
> Volume 25, Issue 9, pp. 498-500.
>
> There appears to be more interest in Xe2 excimer lamps at this point
>
> josh halpern

From:	pooua at aol.com
Subject:	Re: Any excimer knowledgeable people here?
Date:	22 Jan 2005 21:35:57 -0800

I did some searching around to see what I could find along the lines
that you wrote. I don't have very much direct knowledge of excimer
lasers, but I learned a bit about them when I got my degree in laser
technology.

jpsmith123@yahoo.com wrote:

> Thanks for your reply. I haven't yet gotten the paper you referenced,
> but it now appears that a pure xenon excimer laser is at least a
> theoretical possibility.

Xenon excimer lasers are a reality.

> In light of the fact that pure xenon is not corrosive (and this would
> seem to be a big advantage over excimer mixtures containing
halogens),
> I'm thinking there must have been some serious drawback or
> technological obstacle that prevented it from going anywhere.

Apparently, the first excimer lasers were pure noble gas lasers. They
performed poorly, because the gas absorbed about 50% of the beam
produced.

"Obtaining sufficient power input was not enough; one also had to deal
with basic questions of spectroscopy. Indeed, spectroscopy almost
damned excimers to a nonexistent role. Excited-state absorption in the
regions of laser operation resulted in poor lasers on the xenon and
other rare-gas-excited dimer transitions in the VUV, despite highly
efficient energy conversion. Electrically excited Xe at high pressure
can channel roughly 50 percent of the energy deposited in the gas into
Xe2 excimer emission in the VUV. But absorption limits laser
efficiency, and VUV optics at the time experienced significant loss as
well. The discovery of rare-gas halide emission in 1974 and laser
action on these novel molecules in 1975 transformed excimers from an
expensive R&D curiosity into lasers with real potential."

http://www.osa-opn.org/view_file.cfm?doc=%24(%5C%3F%2CK%20%20%20%0A&id=%24)%3C%3B%26JP%20%20%0A

From:	jpsmith123 at yahoo.com
Subject:	Re: Any excimer knowledgeable people here?
Date:	24 Jan 2005 02:47:25 -0800

Hello AES,

Thanks for your reply.

I've been trying to find absorption spectra of xenon dimers on the
internet but I haven't had any luck.

It wasn't intuitive to me that the unstable dimers should be able to
absorb so much more energy.

It also seems counterintuitive that a system that has demonstrated an
energy conversion efficiency of 60% as a lamp would be a poor laser
because of absorption.

Regards,
Joe