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chemistry and so first off really why do

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we even care about sulfur and so

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particularly sulfur compounds are found

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throughout Earth's atmosphere and down

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in the lower troposphere they mostly get

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rained out through because they're

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particularly good at being dissolved in

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the rain but up in the upper

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stratosphere we see this increase in so2

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and this is really important because

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these are a major source of aerosol

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particularly up in the stratosphere and

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so what happens is that sulfur gets

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oxidized to form sulfuric acid which

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thing can then seed aerosol and that

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aerosol does a particularly great job of

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scattering light and so it becomes

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really important when we're looking at

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climates and trying to understand

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different processes that are driving the

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temperature on a planet and so

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traditionally the idea with so2

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chemistry is the so2 reacts with o H to

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make this HS o 3 and that HS o 3

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immediately finds itself running into

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oxygen to make H 0 2 plus s 0 3 and then

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that s 03 through a water catalyzed

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reaction will form sulfuric acid and

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ultimately leads to these aerosol

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particles with through these small

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liquid or solid suspended particles in

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the atmosphere so I guess really the

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question is what's the problem and the

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problem is sulfur compounds have been

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observed throughout our solar system not

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just on earth in particularly there on

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Venus where we have these sulfuric acid

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clouds from 50 to 70 kilometers through

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the atmosphere but once you get above

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those clouds starting about 90

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kilometers there's this massive increase

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in so2 concentration and these increases

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in so2 really exceed any model

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predictions by orders of magnitude two

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or three orders of magnitude and so what

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this really is suggesting it there's

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some sort of chemical source of so2 in

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the middle atmosphere of Venus that we

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don't know about and interestingly

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enough this area has very

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similar conditions to Earth's

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stratosphere in miso sphere so similar

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temperatures pressures and water content

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is specifically what I'm talking about

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and so initially one suggested fix for

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this is some work that was done in the

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Vita group about 15 years ago I'm

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specifically looking at ir overtone

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stretches or overtone o-h stretches and

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the through this overtone you could put

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enough energy in to drive the fatah

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lysis of sulfuric acid to form wha water

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in s 03 and that s 03 can rapidly photo

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lies under standard UV conditions and so

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the idea behind this is that you put in

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your eye our photon you get this oh h

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stretch going and that hydrogen starts

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hopping around the molecule jumping from

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oxygen to oxygen and eventually it finds

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its way to the other oxygen that has a

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hydrogen and we get out water plus s 03

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this is a very fast process so high up

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in the atmosphere in these lower

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pressures it can actually out-compete

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the collisional deactivation and so a

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lot of work was done to actually go and

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measure these overtone stretches these

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going from V equals zero to four and

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five transitions and so you can see

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these happen in the red so in the

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visible this is particularly important

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because UV photons required for

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photolysis of sulfuric acid simply

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aren't available in the atmosphere

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they're filtered out via other

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absorption processes higher up in the

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atmosphere in Venus it's the co2 doing

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it and then interestingly enough these

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transitions do provide enough energy to

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get over this barrier about 40 kcal per

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mole to then go to this s 03 plus water

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and this does a really great job of

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explaining the so2 vertical profile on

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earth unfortunately it's still not good

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enough for Venus so even when this is

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included in the Venus models we are

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still in order or to an order of

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magnitude or two below

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so2 concentrations that are observed and

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so our thought was are there any other

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reservoirs for so2 anything else that

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could be hiding so2 and so what we are

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interested in is looking at sulfurous

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acid this h2s 03 and the idea is that

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through water a water catalyzed reaction

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this could go to s 0 2 plus water and

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unlike sulfuric acid sulfurous acid is

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energetically the unfavored product it's

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actually downhill to go to s 0 2 plus

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water and so it's actually really hard

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to observe this in the gas phase and

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actually hasn't ever been observed in

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the gas phase before and so you can see

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if you start with the sulfurous acid

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it's downhill to these products but you

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do have to go through this barrier so

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it's possible that with this higher

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barrier that there could be this so2 or

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this H to so3 product hiding in the

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I have a big picture no okay so what's

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interesting is we want to know how do

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you get sulfurous acid and how do you

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get up that hill to make that and so

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interestingly enough so2 has this strong

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absorption from 250 to 300 and 10 10

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nanometers in the atmosphere that's not

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filtered out in our atmosphere or and

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Venus's and so the idea is that you can

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excite from the ground state into this

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singlet excited state and then you

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internally convert you walk your way

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down and you find eventually you can get

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this internal conversion to a triplet

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state and so the direct process that

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goes here is forbidden but you can so2

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does make its way here it's known to

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react with organics to make sulfates and

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so the idea is that it can react with

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water to make h2s 03 and so we decided

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to do some experiments trying to

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actually make this sulfurous acid and so

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here i show that transition and what we

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use is a filter to cut out anything

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below about 300 nanometers specifically

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to avoid exciting this deeper UV

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absorption which can actually lead to

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Fatah lysis of so2 and drive other

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chemistry that we aren't interested in

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right now and so what we used is we have

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this simple glass cell with quartz

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windows and we used a this filter to cut

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out the higher energy UV light but let

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through all of this UVA light really and

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then we used a green laser to monitor

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the aerosol content in our cell and so

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interestingly enough when we turn on the

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light we immediately start generating

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aerosol it's not a secret that there's

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something going on it's not something

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you can't see you can visibly see this

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aerosol formation and so looking at the

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controls we wanted to make sure that

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this wasn't something that just shows up

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all the time and so if you start with

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just

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water we don't really see any changes or

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if we just use so2 we don't see anything

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going on but whenever we use a mixture

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of the two we immediately see this

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aerosol formation this decrease and so

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we're looking at this laser going

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through and you can immediately actually

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see the laser going through you can

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watch the particles move through it and

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so this is really exciting this is

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really some new results coming out of

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our group but what we think we're doing

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is actually making this so2 or this h2s

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03 and so I'd like to acknowledge the

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other members of the vitae group who've

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helped me with some of this work

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particularly a Katie Platt who is now a

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professor see you as well as jamie

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donaldson who is the collaborator doing

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a lot of the work on the theory end of

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this looking at the triplet state

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reactions of so2 um as well as our

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funding and thank you guys for your time

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have any questions for Jay all right in

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that case I will use my prerogative and

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ask question on my own so how would you

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go about confirming that it is h 2 sot

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one of the things we want to do is maybe

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use a mass spectrometer as well as i'm

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working and we just got our cavity ring

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down experiment up and going so i could

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actually use the this red cavity ring

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down to look at the o H stretches and

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actually confirm that i'm not making

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sulfuric acid because it is possible

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there are other rats that would take us

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to sulfuric acid we've been careful to

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try and remove all H so we pump the sell

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out overnight to remove everything

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unfortunately if we try and put an o H

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scavenger in the cell it turns out that

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the triplet state so2 really likes to

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react with that o H scavenger and

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generates even more impressive clouds so

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that's actually something that will be

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looking into next as well thank you any

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other questions everyone looks like

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they're about to applaud yeah but we got

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maybe I missed this but do you know what

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the reaction efficiency or what percent

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of sulfur gets transferred converted the

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HS 03 the h2s are three yeah we don't

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yet so that's the next thing that I'm

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really working on is actually getting

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the kinetics down for these sorts of

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reactions so that we can actually feed

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these back into the models and see

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what's going on there okay and I just

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another quick question maybe you haven't

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thought about this but you know if the

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sulfur isotope fractionation would be

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mass dependent during this process um so

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that's the other exciting thing as we

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suspect that it will be and because that

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internal conversion is dependent on the

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masses and that internal conversion is

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related to those vibrations and so

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that's another thing especially with

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that oh h scavenger that we use we want