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so I'm going to go back to the

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astrochemistry session because I'm an

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asteroid chemists and talk about the

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detection of an interstellar molecule so

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as you remember a lot of the motivation

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for those first few talks was the

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detection of new molecules in space so

8
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carbo diam adore carbodiimide however

9
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you want to pronounce it this molecule

10
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right here hnc NH and I promised it

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would be relevant to this section and

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here's why there was a paper very

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recently that said if you want to make a

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Dineen which is in RNA and DNA is the

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connection you can start with this

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molecule here which I've called almost

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adenine because I have no idea how to

18
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pronounce the name ah and this

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conversion happens barrier lessly in the

20
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gas phase in space according to theory

21
00:00:59,720 --> 00:00:57,930
now that's pretty shocking because as we

22
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said almost all of the complex molecules

23
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have to be formed in these Isis normally

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this can happen in the gas phase and if

25
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you look at the subunits of almost a

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Dineen here you've got this backbone c3

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NH but on either whoo on either side and

28
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it may advance automatic there we go r2

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carbodiimide molecules and actually as

30
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it turns out the theorists say you don't

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even need Isis to make almost adenine

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all you need is to carbon I am accused

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in this backbone and all three don't

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even have to be together at the same

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time you can piece this together one by

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one barrier lessly in the gas phase I'm

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not sure I believe them some laboratory

38
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work needs been done but in any case

39
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it's intriguing because this backbone

40
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has been detected for years so if we can

41
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detect this one now we have a potential

42
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route for the synthesis of a nucleobase

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in the gas phase in space which i think

44
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is pretty cool so moving on to how we

45
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might detect a molecule in space just a

46
00:02:04,789 --> 00:02:02,369
brief overview there's two main methods

47
00:02:06,529 --> 00:02:04,799
one is to use infrared spectroscopy so

48
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using something like the Keck telescope

49
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here and this is optical light so we use

50
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mirrors and cameras and this is looking

51
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at vibrations of molecules all right the

52
00:02:19,309 --> 00:02:18,750
other option which is what I'm going to

53
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talk about

54
00:02:22,929 --> 00:02:20,999
the way most molecules are detected is

55
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rotational spectroscopy so that's

56
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predominantly done in the radio or the

57
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microwave or sub millimeter so that's

58
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using electronics so use oscillators

59
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generate frequencies of light on that

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time scale and you use radio telescopes

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this is one from the now-defunct

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combined array for research and

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millimeter wave astronomy to detect

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rotational transitions of the molecules

65
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so how does that work well if you want

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to detect a molecule in space first you

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have to understand what you're looking

68
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for so you go into the lab say for

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carbon monoxide here one of the most

70
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prevalent molecules in space and you

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take the spectrum this infrared spectra

72
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carbon dioxide collected in the lab you

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go to your telescope you collect the

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spectrum of the exact same frequency

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00:03:12,589 --> 00:03:10,109
region in space and then you compare all

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right and so if you're a Praetorian

77
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spectrum in your infrared spectrum of

78
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the space match up then you've detected

79
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the molecule now there are a couple

80
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constraints to this if I have this

81
00:03:25,789 --> 00:03:23,040
laboratory spectrum I have this large

82
00:03:27,289 --> 00:03:25,799
peak that was measured there and say I

83
00:03:29,420 --> 00:03:27,299
went out in space and I measured it in

84
00:03:31,520 --> 00:03:29,430
that peak was missing that's a little

85
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concerning you can't just turn Peaks on

86
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and off these are frequencies that are

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intrinsic to the molecule so if you're

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missing something that quantum mechanics

89
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and your experiment says should be there

90
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then something is going on and you don't

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actually have a detection of this

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molecule it's an incidental transition

93
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from something else right this is not

94
00:03:50,839 --> 00:03:49,290
just isolated CO and there you see those

95
00:03:53,119 --> 00:03:50,849
Peaks from other molecules there that

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00:03:54,170 --> 00:03:53,129
could be interfering so that's that's

97
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the most important thing to remember

98
00:03:57,199 --> 00:03:55,680
going forwards you have to have every

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line that you measure in the lab of a

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preacher full intensity show up in your

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spectrum from space so here's

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carbodiimide carbodiimide it's actually

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a tautomer of cyanamid here this

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molecule is detected in the interstellar

105
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medium in 1975 so you might say well why

106
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didn't people just go look for carbon

107
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diamont and the problem is that this

108
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tautomer is for kcals per mole higher

109
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and energy which doesn't sound much to a

110
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chemist but in space where the

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temperatures are cold it's not actually

112
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much of it so at room temperature here

113
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about 1% of a bottle would be covered i

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omit but in

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space where we're looking at

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temperatures of a much smaller so 10k or

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50k that that drops to a tenth of a

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percent or 100th of a percent but about

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ten years ago some folks said well if

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you put cyanamid in water ice and as we

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heard from Brandon water ices the most

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predominant ice in the interstellar

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medium you can actually get an

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enhancement of this carbon diamond

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something like four percent or thirteen

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percent of the cyanamid abundance all of

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a sudden that's actually a detectable

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abundance using radio astronomy so we

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went and took a look we looked in the

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center of our galaxy in a region called

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Sagittarius b2n this is where almost all

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of the new molecular detection to date

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have been made so it's an incredibly

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chemically rich source and we actually

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already had radio Spectre taken towards

136
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that source so this is part of the

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prebiotic interstellar molecular survey

138
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and we just took a broad frequency scan

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from about 300 megahertz up to 50

140
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gigahertz covered everything at once and

141
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we can say well where do the laboratory

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data say that carbon diamond should be

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found and here's the red line so we

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don't have coverage here at 16 gigahertz

145
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unfortunately but everywhere else

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including these down here at four

147
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there's a little black dot there we have

148
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some spectra so we can go and compare

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this is a cartoon of what we would

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expect to see the most intense lines up

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at 45 as we go up in frequency so we

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step through and see what our

153
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observational spectra show us so 4

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gigahertz we have two lines just like we

155
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would expect to see 16 gigahertz we

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don't have coverage for 25 gigahertz we

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have a line here this is another

158
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interfering transition of methanol so

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that's hiding our line there and at

160
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forty five gigahertz we have a line

161
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right there and this one we don't have

162
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coverage for but at 36 gigahertz

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remember that was going to be the second

164
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most intense transition set of

165
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transitions in the line there's

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absolutely nothing here it's just dead

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noise in the middle so just like not

168
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having one of those transitions

169
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recovered monoxide now we have a problem

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slab data say it should be there and the

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observational data don't see it there

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these are really strong and that one's

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pretty big and this one's not negligible

174
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so we were wondering exactly what was

175
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going on here and whether or not

176
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something was happening that we weren't

177
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quite understanding and and to give you

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an answer for that we have to go do a

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that's what we expected a brief review

180
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of laser theory or in this case maser

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the microwave equivalent of a laser ah

182
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so if you can imagine a four level

183
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energy system for your molecule with

184
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fast transitions between three of them

185
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and at a very slow transition here you

186
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just put some molecules in here like

187
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marbles and let them flow around the

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system as I'd like to do absorbing and

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emitting energy those go really fast and

190
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eventually you just build up a large

191
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population up here in III that's waiting

192
00:07:36,180 --> 00:07:33,700
to undergo this very slow transition now

193
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when one of them goes it stimulates all

194
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of them to go at the same time and so

195
00:07:41,550 --> 00:07:39,370
you get a coherent emission of radiation

196
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much more intense than you would expect

197
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otherwise from just one molecule going

198
00:07:49,440 --> 00:07:46,780
at a time so a laser pointer works and

199
00:07:52,710 --> 00:07:49,450
that's the way that the transitions that

200
00:07:54,240 --> 00:07:52,720
we're going to look at now might work so

201
00:07:55,950 --> 00:07:54,250
if we go and look at the energy level

202
00:07:58,680 --> 00:07:55,960
diagram for carbodiimide it's more

203
00:08:00,930 --> 00:07:58,690
complicated but we can step through it

204
00:08:03,330 --> 00:08:00,940
the same way so these are the two energy

205
00:08:07,140 --> 00:08:03,340
levels involved in the 4 gigahertz

206
00:08:09,180 --> 00:08:07,150
transitions and there's fast transitions

207
00:08:11,220 --> 00:08:09,190
out of the ground state as fast

208
00:08:13,320 --> 00:08:11,230
transitions into the excited state and

209
00:08:15,420 --> 00:08:13,330
there's a slow transition between them

210
00:08:17,240 --> 00:08:15,430
so you can see it's very simple here to

211
00:08:19,470 --> 00:08:17,250
build up a population inversion up

212
00:08:21,840 --> 00:08:19,480
piling up in this upper excited state

213
00:08:25,020 --> 00:08:21,850
and then undergoing amazing transition

214
00:08:26,840 --> 00:08:25,030
here amplifying the the intensity of

215
00:08:29,790 --> 00:08:26,850
that transition in our observed spectra

216
00:08:33,300 --> 00:08:29,800
this holds for the 25 gigahertz and the

217
00:08:35,070 --> 00:08:33,310
45 gigahertz lines as well if you go to

218
00:08:37,530 --> 00:08:35,080
the 36 gigahertz lines which we don't

219
00:08:40,230 --> 00:08:37,540
see again here's the transitions

220
00:08:42,120 --> 00:08:40,240
involved we have fast transitions into

221
00:08:43,490 --> 00:08:42,130
the upper state fast transitions out of

222
00:08:46,020 --> 00:08:43,500
the ground state and a slow transition

223
00:08:48,270 --> 00:08:46,030
between them so that's initially

224
00:08:49,650 --> 00:08:48,280
concerning it should be amazing to but

225
00:08:51,480 --> 00:08:49,660
because the energy level structure is

226
00:08:53,460 --> 00:08:51,490
slightly different there's also a fast

227
00:08:55,890 --> 00:08:53,470
transition out of this upper state down

228
00:08:57,600 --> 00:08:55,900
to another lower one so that means you

229
00:08:59,010 --> 00:08:57,610
can't build up any population up here

230
00:09:00,040 --> 00:08:59,020
because while it's waiting the undergo

231
00:09:01,930 --> 00:09:00,050
this it says screw that

232
00:09:04,780 --> 00:09:01,940
I'm going to go down here instead and it

233
00:09:07,120 --> 00:09:04,790
just piles down really fast so we won't

234
00:09:08,949 --> 00:09:07,130
see any enhancement in amazing emission

235
00:09:11,860 --> 00:09:08,959
there so that line shouldn't be any

236
00:09:13,900 --> 00:09:11,870
brighter than it would normally be so if

237
00:09:16,360 --> 00:09:13,910
you go back take a look at our spectra

238
00:09:18,910 --> 00:09:16,370
once again is the 4 gigahertz 25

239
00:09:21,430 --> 00:09:18,920
gigahertz 36 and 45 I haven't shown the

240
00:09:23,680 --> 00:09:21,440
other corresponding ones down here these

241
00:09:27,160 --> 00:09:23,690
four are these three can undergo amazing

242
00:09:29,079 --> 00:09:27,170
so you see the lines there that's the

243
00:09:31,090 --> 00:09:29,089
one that can't undergo amazing so we

244
00:09:34,210 --> 00:09:31,100
don't see any line there now what this

245
00:09:35,800 --> 00:09:34,220
means is that this population if it

246
00:09:39,069 --> 00:09:35,810
weren't amazing wouldn't be detectable

247
00:09:41,170 --> 00:09:39,079
at all right is everything was happening

248
00:09:42,670 --> 00:09:41,180
normally this would be the second

249
00:09:44,710 --> 00:09:42,680
brightest transition in the spectrum

250
00:09:48,069 --> 00:09:44,720
that means that we wouldn't see these at

251
00:09:50,019 --> 00:09:48,079
all ah this is very little carbon

252
00:09:52,120 --> 00:09:50,029
diamond out there it's not very much of

253
00:09:53,710 --> 00:09:52,130
it but we were able to detect it because

254
00:09:55,540 --> 00:09:53,720
it's undergoing these amazing

255
00:09:57,430 --> 00:09:55,550
transitions and this way we can get

256
00:09:59,319 --> 00:09:57,440
around the rule of having to see every

257
00:10:00,970 --> 00:09:59,329
transition as measured in the lab by

258
00:10:03,160 --> 00:10:00,980
explaining with physics why some of them

259
00:10:06,370 --> 00:10:03,170
are brighter than others in this

260
00:10:09,250 --> 00:10:06,380
specific environment so we published

261
00:10:10,510 --> 00:10:09,260
this a few years ago and hopefully

262
00:10:12,760 --> 00:10:10,520
somebody will figure out a way to make

263
00:10:15,100 --> 00:10:12,770
nucleobase out of it in the lab now that

264
00:10:17,350 --> 00:10:15,110
we have it there um so I think I've

265
00:10:24,850 --> 00:10:17,360
occupied almost enough of our time ah

266
00:10:31,060 --> 00:10:24,860
thank you we can take a question before

267
00:10:35,769 --> 00:10:31,070
we transition thank you super chair so

268
00:10:38,440 --> 00:10:35,779
that was amazing so how come you don't

269
00:10:41,590 --> 00:10:38,450
get these in the lab to get the amazing

270
00:10:42,910 --> 00:10:41,600
transition yeah you can but you have to

271
00:10:45,819 --> 00:10:42,920
be careful about the way that you

272
00:10:47,290 --> 00:10:45,829
excited um so to get the population to

273
00:10:49,389 --> 00:10:47,300
that upper state the way it works in

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space is that at least in this

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environment we're not certain either you

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RAM molecules into one another and use

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the energy from that collision to

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populate the upper state or you pump

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higher energy states with radiation from

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further in the electromagnetic spectrum

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far infrared radiation unfortunately

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this region has both as a possibility so

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we have observations in now actually to

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untangle which one's happening

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so you could do it in the lab you just

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have to make sure to provide one of

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those conditions so you said their gas

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phase reactions with this but you also

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said that it is primarily on ice so so

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what happens is that carbon diamond will

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form from cyanamid in the ice and then

292
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get liberated into the gas phase once

293
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it's in the gas phase it can't get over

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the barrier to go back to cyanamid so

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it's trapped okay all right I has this

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actually been found in a comet or

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meteorite yet actually I don't know no

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it hasn't and what's the barrier for

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inversion back and forth it's several

300
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hundred wave numbers in the gas phase

301
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once you put it in that and the ice the

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barrier drops to zero is there another

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one real quick how can people say the

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reaction is barrier diseases just by

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computational calculation yeah all the

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all of the theories of ours is