Reac%onofAlN
+withH
2O
H2isaDrac,ngmuchaDen,onasaninnova,veenergycarrieralterna,vetoconven,onalfuels.
OneofthemethodstoproducehydrogenisauseofAloritsalloystoreduceH2OtoH2becauseofits
efficiency,safety,andenvironmentalfriendliness.
+
AlN +H2O→?
Iondeflector
H2OwithHegas(PH2O,PHe)at300K
Iondeflector
Reac,oncell
Q-massspectrometer
(Iden,fica,onofproducts)
Quadrupole mass filter
(Sizeselec,on)
Coolingcell
77K
liq.N2
Iondetector
(Observa,onofreac,onproducts)
Magnetron-spuDer
cluster-ionsource
(AlN+,N=2−19)
Sizedependenceofreac%onproducts
Ecol:about0.2eVinthecenterofmassframe
N= 2
N= 3
N= 4
N=3−5:Noreac,onproducts
N= 5
Intensity / arbitrary units
N= 6
N= 7
N=2,6−13:AlNO+orAlN(H2O)+
selec,veforma,on
N= 8
N= 9
N = 10
N = 11
or
N = 12
N = 13
N = 14
N = 15
N = 16
N=14−19:bothAlNO+andAlN(H2O)+
N = 17
N = 18
N = 19
Mass shift from the reactant AlN+, Δm / amu
Undertheconst.collisionenergycondi,on,
whethertheoxida,onreac,onproceeds
dependsonthesize.
12
HOMO-LUMO energy gap /eV
Intensity / arbitrary units
Sizedependenceofthereac%onproducts
The situation is some
For positively charged A
ous peaks in the HOMO
+
+
+
AlN +H2→AlN(H2O) −−−→AlNO +H2 Al#9 , Al13# , and Al15# . Th
in the jellium model as th
Thebarrieroftheoxida,onreac,ondependsonsize.
electrons, just enough fo
from Fig. 5!a" that $E #
N=6,8,10,11,12:Lowbarrier
n
HOMO–LUMO gap is co
N=7,9,13:Highbarrier
No such correlation exists
N= 6
For negatively charge
Apossibleexplana,onisbyHOMO-LUMOenergygaps.
exhibit odd–even alteratio
N= 7
having larger HOMO–LU
%see Fig. 8!c"&. Of particu
"
"
,
and
Al
Al
7
11 . It is clear
N= 8
the electronic shells and
LUMO gap. If aluminum
mono-valent as discussed
N= 9
electrons and hence its la
consistent with electronic
N = 10
34 electrons also is a clus
(RaoandJena,
hence should have a large
6 7 8 9 10 11 12 13
J.Chem.Phys.111,1890,1999)
Size, N
Note that these are consis
N = 11
2R2
these clusters as seen fro
2e
+
polarizabilityofAlN : αAlN+≈
5!c". However, the large
ΔEHL
neither consistent with th
N = 12
their relative stabilities. A
AsmallΔEHLcausesalargepolarisability,andalargeinternalenergyof
HOMO–LUMO gap whic
[AlN(H2O)+]*.
"
N = 13
bility than Al14
, but it doe
However,dipole–induceddipoleinterac,onisintherangeof0.01–0.1eV:
closure.
Δm / amu
thisisgenerallycomparableorlowerthantheion–dipoleinterac,on.
Collision-energydependence（N=11）
PH2O=1.9×10−3Pa Ecol=0.21eV
1.0
3.0
Eint+Ecol>Et
Et
Energy
0.5
2.5
(a)
PH2O=1.4×10−3Pa Ecol=0.18eV
0.5
1.5
Decelera,onoccurredbeforereac,ngwithH2O.
Eint+Ecol<Et
(b)
0
1.0
Et
Energy
Intensity (a. u.)
Intensity (a.u)
0
2.0
0.5
0.5
0.0
0
PH2O=0.9×10−3Pa Ecol=0.15eV
(c)
14
14
16
18
16
18
Δm /amu
Mass
/ amu
20
20
The reac,on proceeds favorably at a higher collision
energy; the internal energy of the precursor complex
∗
+
[Al11(H2O) ] wouldbethedrivingforceofthereac,on.
Summary
Reac,onofAlN+withH2O
AlN++H2O
[AlN(H2O)+]*
AlNO++H2
∗
+
TheH2genera,onreac,onoccursonlyif[AlN(H2O) ] hashighinternalenergy.
(M.Arakawa,K.Kohara,T.Ito,andA.Terasaki,Eur.Phys.J.D67,80,2013)