6K. H. Kim et al., Nature 518, 385 (2015)

2015{2¬19¤DgƝ=ãƴƧƱ
原子同士が結合して新しい分子が生まれる瞬間をX...

http://www.kek.jp/ja/NewsRoom/Release/2015021..

¸ ǱDgǮǟǭƝøŔĀ|ƙǜƺǦǑôƝ§Ŕ1ĥĕƴƪƖÏkƴlÞğ ǱDgŔƝ>iĉNƝàŇõƴ1g=ãƜƮƕƗžƒ

ESEARCH LETTER

SPring-8Ɠƙa>Ɲ7 http://www.kek.jp/ja/NewsRoom/Release/2015021...
Ɲś¾ãƓƅƓƁŶ LETTER RESEARCH
原子同士が結合して新しい分子が生まれる瞬間をX...
ĵţŃƛ>iĉNƝa>ƴSACLAƴŽƙǛǂôƘƝa>ƝŁ ƴ=ãƘJĕ

Radial intensity, r2S(r) (a.u.)<100 fs, 15 keV
X-ray pulses~100 fs, 267 nm laser pulses
10 ns

24

6r (Å)FT

8qΔS(q) (a.u.)

2 3

10

SACLAĵţŃ
200 http://www.kek.jp/ja/NewsRoom/Release/2015021...
fs
Bent
F2 = 4.81

原子同士が結合して新しい分子が生まれる瞬間をX...
[Au(CN) –] in waterƴ HÏàùśxòøŌŪzƖǩȌƐƴ

X-ray arrival, 0 s–5 ps
http://www.kek.jp/ja/NewsRoom/Release/2015021...

10 ps
10 ns

200 fsBent

SPring-8
Ƭƕƃư

Time

200 fs–5 psExperiment
TheoryrtòøŌŪîŕimInzÚÕƣxŧòjt^fÏàžƏ¦º±ǙÝjtÏàùśȁƘlhvuIĂàzŌŪĉLĵËųżLýōĉz

原子同士が結合して新しい分子が生まれる瞬間をX...
ŧòxs^tƹǙlhvxċǪjoJ
10 psbExperiment

TheoryTime-dependent
Au–Au pairs
Residuals
200 fsResiduals
structural changes
10Linearpsƴ HÏàùśxòøŌŪzƖǩȌƐƴLinear'!z«¸+Ÿŏrt¦º±ȁƘlhvu®²¦ƀzÙÜN¸uĂàzùdƖǩlhvcŮōvwroJÀƑƥu{ƚǭǂx
10F2ns= 1.70

Difference scattering intensity, qΔS(q) (a.u.)XďÑË ar2S(r) (a.u.)ab

10 ps'!z«¸+Ÿŏrt¦º±ȁƘlhvu®²¦ƀzÙÜN¸uĂàzùdƖǩlhvcŮōvwroJÀƑƥu{ƚǭǂxrtòøŌŪîŕimInzÚÕƣxŧòjt^fÏàžƏ¦º±ǙÝjtÏàùśȁƘlhvuIĂàzŌŪĉLĵËųżLýōĉzŧòxs^tƹǙlhvxċǪjoJ

CCD detector

10 ns
12

3

4

5

62q (Å–1)
46q (Å–1)of the S1 state using the experimentalFigure 3 | Structure determinationƴ HÏàùśxòøŌŪzƖǩȌƐƴ

4628r (Å)

better fit than the bent structure, which has the same Au–Au–Au bond angle asscattering curve at 200 fs time delay in momentum space and real space.
the S0 state, thereby indicating that the bent-to-linear transition is completed at'!z«¸+Ÿŏrt¦º±ȁƘlhvu®²¦ƀzÙÜN¸uĂàzùdƖǩlhvcŮōvwroJÀƑƥu{ƚǭǂx200 fs time delay. b, Corresponding experimental (black) and theoreticala, Theoretical difference scattering curves (red) for linear (upper) and bent
gure 1 Femtosecond time-resolved X-ray solution scattering at theXFEL
scatteringdifference
patternazimuthally,
subtracting(red) RDFs,rS(r). It can besolvent
seen that in the bent structure R13 is too small to fit(lower)
structurestwo-dimensional
shown together with the experimental
scatteringŧòxs^tƹǙlhvxċǪjoJ
the experimental
RDF
at 200 fs.
curve at 200 fs (black).
The residuals (blue)
between the theoretical
andtransformtheility and the data analysis. a, The photochemical reaction of solutes
contributions,performinga Fourier(FT) andcompensating
for theexperimental curves are shown together. The linear structure gives a much|ǮǲǄǲƴƗƒƙƂƝōőƝ
ƯƲƒ>iĉNƝ»}Yŷō-ōƝŔ>iĉNƝa>ƴŶSACLAƝǜƺ
pplied by a liquid-flowing
system is triggered by a femtosecond optical laser ƝĉNŒƴǃǝÅƝ1ĥĕƘŶǬƷǭǌ
depletion of the initial solute contribution due to photochemical reaction,lse. Subsequently, ǦǑôǘǭǇƜƮƱa time-delayed X-ray pulse synchronizedwith thescattering
laser curves,weobtain
one-dimensional
real space
as shown
thedelays
plotfromat themeasured
at variousintime–800 fs to 300 ns are shown in
qDS(q,t), where
q is the momentum RDFs
transfer inbetweenƘÏkƸǦƜĤolse probes the structural dynamics of the reaction. The scattering patternis andtop
left. These
displayinteratomic
distancesof transient
speciescurves
andshow distinct oscillatory features
Fig. 2a. The
difference scattering
the incident
the elasticallyscattered
X-raythewaves
and DS is the difrtòøŌŪîŕimInzÚÕƣxŧòjt^fÏàžƏ¦º±ǙÝjtÏàùśȁƘlhvuIĂàzŌŪĉLĵËųżLýōĉzƴ HÏàùśxòøŌŪzƖǩȌƐƴ'!z«¸+Ÿŏrt¦º±ȁƘlhvu®²¦ƀzÙÜN¸uĂàzùdƖǩlhvcŮōvwroJÀƑƥu{ƚǭǂx–alongq axis, which2indicate
large structural changes in [Au(CN)2 ]3ferenceas
betweenproducts.
scattering intensities
before thelaserlengths
excita- ofrtòøŌŪîŕimInzÚÕƣxŧòjt^fÏàžƏ¦º±ǙÝjtÏàùśȁƘlhvuIĂàzŌŪĉLĵËųżLýōĉz
ected by a fast two-dimensional charge-coupleddevice (CCD) detector
In this measured
way, Au–Au
bondthethe[Au(CN)2 ]3 complex can betion (that is, at a negativetime delay) and after the laser excitation (that during the formation of covalent Au–Au bonds. Considering that theƴ HƚòøŌŪzĐÇxǦ_ÏàžƏŧòŅlǙÝ¥N¢ŧòxs^tƹǙlhvxċǪjoJ
own at the bottom. We measure time-resolved
scattering patterns whileidentified
withsub-ångströmaccuracy,andthetime-dependent
structuralƚȎźÛ'vƚȎźÚ'( @1@>-91>xagùȐÏǛåĔJůȅ{ÈĂàbzĵËǴƵu]I­N{ÏàÂzÈÈÜĵËǴƵúis, at a positive time delay).
Theexperimental
difference scattering curves oscillatory features appear distinct
even after the shortest time delay
rying the time delay between the laser and X-ray pulses. b, By integrating the changesof the metal complex can be determined in real time.
lJ1g¹ńƝƻǕǭƾǲƙ§Ŕa>)>iEƝņĚƜŽe TRXSS experiment at1g¹ńƝa>
an XFEL facility7 (SACLA), we were able toudy the ultrafast structural dynamics of bond formation in [Au(CN)2–]3
solution with subpicosecond time resolution and sub-ångström spal resolution.
The femtosecond TRXSS experiment performed in this study is shownhematically in Fig. 1, and the details of the experimental procedured the analysis are described in Methods and Extended Data Table 1.

aand Au–Au bond shortening (<500 fs)
For the sample,Bent-to-linear
we usedrelaxation
an aqueoussolution of Au(CN)2– at a concentration of 300 mM,
becauseina solution of this concentration the12Further Au–Au bond shortening (1.6 ps)
3[Au(CN)2–]3 trimer has much higher absorbance at 267 nm than does
Tetramerformation (3 ns)
a monomer or a dimer of Au(CN)2– (SupplementaryInformation).
As12
3S
Linearexcitation
staggered structure
a result, thelaserat267
nm
usedinourTRXSS
experiment(longer distance)–predominantly excites the [Au(CN)12 the3 other42 ]3 trimer while excitingT
Linear staggered structure(shorter distance) we obtained difference
species negligibly. From
2 the TRXSS experiment,ƴ HƚòøŌŪzĐÇxǦ_ÏàžƏŧòŅlǙÝ¥N¢

ƚȎźÛ' vƚȎźÚ' ( @1@>-91>xagùȐÏǛåĔJůȅ{ÈĂàbzĵËǴƵu]I­N{ÏàÂzÈÈÜĵËǴƵú

Energy1267 nmlJ1

31Tetramerƴ HƚòøŌŪzĐÇxǦ_ÏàžƏŧòŅlǙÝ¥N¢
ƚȎźÛ' vƚȎźÚ' ( @1@>-91>xagùȐÏǛåĔJůȅ{ÈĂàbzĵËǴƵu]I­N{ÏàÂzÈÈÜĵËǴƵú
Scp1

p2

p3

– 800 fs

– 800b fs

200 fs200 fsBent
1.6structure
psStructural parametersS0ƴ HƚòøŌŪzĐÇxǦ_ÏàžƏŧòŅlǙÝ¥N¢

S0100 ns

Tetramer
Reaction progress

S0ż~9ƘƉƲƒŗNƘƞōƸƼRRRǰO`ƞƲ©Ɓƕƒ¹ńƴƖ—
3.87 ± 0.04 Å
3.30 ± 0.06 Å
5.56 ± 0.11 Å
R12Species

700 fs

700 fs

3 ns

T1

S1

Concentration

0blJ

a

23

1334

2.81 ± 0.03 Å

5.63 ± 0.09 Å—

5.41 ± 0.11 Å—lJ

S1
1.7 ps2.82 ± 0.04 Åƴ HƹǙioòøĵËƜċxÏàzÔċȌƐƴ

1.7 ps100 ps300 ps
1 ns
3 ns

T1

3.2 ps2.71 ± 0.03 ÅKƚȎźňÚIÈ»ÜxĈ^òøĵËcÔċiIÈÈÜĵËǴƵ{ĬŨjňŸųzžƏġroâj^ÏàcÔ' –1012345Tetramer
0.06 Å 10  2.62
Å
2.88 ± 0.04 ÅK ­ƀÚIixÈÈĵËÜǴƵcǏ^žƏxŧòl(10102.89 ±10
10 ± 0.0610
10 —Radial intensity, r2S(r) (a.u.)

10 ps30 ps)ƴƗƱ
2.70 ± 0.05 ÅKǥ^đçuƜċiošËïu{È»Öţ{ǡǮcrožƏġs' 

3.2 psK 

10 psōƸƼǰŔƜż>iĉNƁàƉƲŶō-ōŔĉTime (ps)NķŘƞÍtƊëďÛƝ¹ńƝ¡Ɗż1gƣ
contraction of Au–Au bonds, and then to a tetramer through formationofS­ƀÚIÈȗï_ÄsþĴuixâj^žƏġsÏàcÔċi@1@>-91>J­ƀÚx{òøĵË{ŹƅjSubsequently, the S1 state transforms first to the T1 state, with furtherFigure 4 | Mechanism of photoinduced bond formation in [Au(CN)2–]3.
30 psthe1
a, Femtosecond TRXSS reveals
dynamics and the atomic movements
Experimentd in real time with sub-ångströmassociated with the Au–Au bond formation
100 psstate
withweakly
bound Au atoms in a bent geometry
spatialresolution.
TheS0ƴ HƹǙioòøĵËƜċxÏàzÔċȌƐƴ
S0transforms
to the S1 state with tightly bound Au atoms in a linear geometry.
Kǥ^đçuƜċiošËïu{È»Öţ{ǡǮcrožƏġs'100Ǔǖô
3/5'ƜƱ

300 psRadial intensity, r2S(r) (a.u.)

Difference scattering intensity, qΔS(q) (a.u.)ƚȎźÛ' vƚȎźÚ' ( @1@>-91>xagùȐÏǛåĔJůȅ{ÈĂàbzĵËǴƵu]I­N{ÏàÂzÈÈÜĵËǴƵú

Theory1.6Ǜǂô Au–Au pairs

another Au–Au bond. b, Structural parameters of each state and their standard
R12:determined
3.30 ± 0.06 Å from 50 independent measurements.
errors2015/02/24 17:11

R23: 3.87 ± 0.04 Å
R13: 5.56 ± 0.11 ÅKƚȎźňÚIÈ»ÜxĈ^òøĵËcÔċiIÈÈÜĵËǴƵ{ĬŨjňŸųzžƏġroâj^ÏàcÔ' 

1 9 F E B R U A RY 2 0 1 5 | VO L 5 1 8 | N AT U R E | 3 8 71 nsK ­ƀÚIixÈÈĵËÜǴƵcǏ^žƏxŧòl(K SACLAƜƮưŶǛǂôǱǓǖôǱǤƸ
10 nsƿǯôƜƳƒƱºŸƛ§ŔǇǁǲ
30 ns
3/5ǭƝÞıƴǦǲǚǲƙƊƗ
100 nsrights reserved©2015 Macmillan Publishers Limited.RAll
12: 2.81 ± 0.03 ÅS1­ƀÚIÈȗï_ÄsþĴuixâj^žƏġsÏàcÔċi@1@>-91>J­ƀÚx{òøĵË{ŹƅjR23 : 2.82± 0.04 Å
3 ns
R13: 5.63 ± 0.09 ÅT110 ns

ƴ HƹǙioòøĵËƜċxÏàzÔċȌƐƴ

30 ns

ƉƯƜō-ōĉNŔķŘƁîż¹ńƜa>

T1Kǥ^đçuƜċiošËïu{È»Öţ{ǡǮcrožƏġs' 

R12: 2.70 ± 0.05 Å
R23: 2.71 ± 0.03 Å
R13: 5.41 ± 0.11 Å3Ǔǖô 

2015/02/24 17:11

KƚȎźňÚIÈ»ÜxĈ^òøĵËcÔċiIÈÈÜĵËǴƵ{ĬŨjňŸųzžƏġroâj^ÏàcÔ'
100 nsK ­ƀÚIixÈÈĵËÜǴƵcǏ^žƏxŧòl( 300 ns

24
q (Å–1)

63/5K Tetramer

24ƴ HƹǙioòøĵËƜċxÏàzÔċȌƐƴ

6r (Å)

810

2

R12: 2.88 ± 0.04 Å
R23: 2.62 ± 0.06 Å­ƀÚx{òøĵË{ŹƅjR34: 2.89 ± 0.06 ÅōőƴƪŽƖGưĽƵƘƉƯƜ¡Ɗż¹ńƴƖ1gƁàVŌ­ƀÚIÈȗï_ÄsþĴuixâj^žƏġsÏàcÔċi@1@>-91>J300 ns4Kǥ^đçuƜċiošËïu{È»Öţ{ǡǮcrožƏġs' KƚȎźňÚIÈ»ÜxĈ^òøĵËcÔċiIÈÈÜĵËǴƵ{ĬŨjňŸųzžƏġroâj^ÏàcÔ' 

68r (Å)1012

2015/02/24 17:11

Time-dependent structural changes[Au(CN)2–]3.
K of­ƀÚIixÈÈĵËÜǴƵcǏ^žƏxŧòl(indicates the standard error determined from 50 independent measurements

gure 2 |K ­ƀÚIÈȗï_ÄsþĴuixâj^žƏġsÏàcÔċi@1@>-91>J­ƀÚx{òøĵË{ŹƅjThe vertical black dotted lines indicate theExperimental difference scattering curves, qDS(q),measured at various time (that is, 50 scattering images).
temporal positions corresponding to the time constants of the three kinetic
ays from –800 fs to 300 ns (black). For clarity, only data at selected timeays are shown. a.u., arbitrary units. b, RDFs, r2S(r), obtained by Fourier sine components. d, Species-associated RDFs of the four structures obtained fromanalyses(black)nsformation of qDS(q) after subtracting
solvent contributions. The RDF of the singular value decomposition and principal-component
3/5
2015/02/24
17:11