11

Infrared Spectroscopy of Ammonium IonInfrared Spectroscopy of Ammonium Ion

MG03:MG03: Sub-Doppler Spectroscopy of NDSub-Doppler Spectroscopy of ND33HH++ Ions in the NH Stretch Mode Ions in the NH Stretch Mode

MG04:MG04: Infrared Spectroscopy of Jet-cooled NDInfrared Spectroscopy of Jet-cooled ND22HH22++ Molecular Ions: Molecular Ions:

The Symmetric and Antisymmetric NH Stretch ModesThe Symmetric and Antisymmetric NH Stretch Modes

CHIH-HSUAN CHANG, Grant Buckingham, and David J. NesbittJILA, NIST, University of Colorado

Department of Chemistry and Biochemistry, University of Colorado at BoulderBoulder, CO 80309

International Symposium on Molecular Spectroscopy68th meeting, Jun17-21, 2013, OH

22

IntroductionIntroduction

• NH4+ ion is a crucial species in acid-base chemistry

and aqueous solution

• Carrier of spectra in the Young Stellar Objects (YSO)

33

Located approximately 12,000 light-years away from Earth, in the constellation Sagittarius

AstronomyAstronomy

Gibb et. al. The Astrophysical J. 536,347(2000)W. A. Schutte and R. K. Khanna, A&A, 398, 1049(2003)

NH4+

44

H3+

H3O+ OD3+HOD2

+H2OD+

Isotope-substituted Ion SpeciesIsotope-substituted Ion Species

NH2D2+NH4

+ NHD3+ NHD3

+ ND4+

• Symmetry reduction results in the multiple non-degenerate vibrations and intensity dilution

55

Fundamental Vibration ModesFundamental Vibration Modes

Jacox and Thompson, PCCP, (7) 765, 2005 Intensity in unit of km/mol.

Oka group

Saykally group

Oka group

Saykally group

Nakanaga and Amano

Park et. al.(1996)

66

Frequency calibration Frequency calibration Polarization-stabilized HeNe laser Polarization-stabilized HeNe laserLaser scanning Laser scanning Fabry-Perot interferometer Fabry-Perot interferometerConcatenation Concatenation Marker cavity Marker cavity

Sub-Doppler Resolution Infrared SpectrometerSub-Doppler Resolution Infrared Spectrometer

• Absorption noise level ~ 1.310-3 %• Absorbance ~ 0.055 %• Signal to noise ratio ~ 45• Sub-Doppler resolution ~ 120 MHz (H2 gas)

Chemical reaction route : H2 + e- H2

+ + 2e-

H2+ + H2 H3

+ + H H3

+ + ND3 ND3H+ + H2

H3+

+ ND2H ND2H2+ + H2

Discharge Slit-jet

General Advantages: Sub-Doppler resolution (60 MHz) Rotational cooling (15 K) High density of radicals or cation.

mirrormirror

Slit jet

88

Band Type Structure of TransitionBand Type Structure of Transition

b

c

//

1 6 1

Oblate Top (A = B > C)Asymmetric Top( = 0.27)

99

Nuclear Spin StatisticsNuclear Spin Statistics

• ND3H+ ion

123 1total total 1 2 or total A A

1 210 1 8ns A A E

KK RotRot ggnsns

00 J even J even AA11 1111

J oddJ odd AA22 1111

3n3n±±11 EE 16163n3n±±33 AA1 1 + A+ A22 2222

ggnsns

KKa a + K+ Kc c = even= even 1515

KKaa+ K+ Kcc= odd= odd 2121

(e)(e) (v)(v) (r)(r) (ns)(ns) (total)(total)

aa11 aa11 aa11 bb22 bb1 1 or bor b22

aa11 aa11 bb11 aa11 bb1 1 or bor b22

aa11 aa11 bb22 aa11 bb1 1 or bor b22

aa11 aa11 aa22 bb22 bb1 1 or bor b22

• ND2H2+ ion

1 221 15ns A B

12 1total total 1 2 or total b b

12 1total total

total e v r ns

total e v r ns

1: ( =0, 1, 2...)

11: ( = ,...)

2

Boson particle I

Fermi particle I

1010

Global View Region of NH Modes Global View Region of NH Modes

ND2H2+

Symmetric mode(1)ND2H2

+

Antisymmetric mode(6)ND3H+

NH stretch mode(1) NDH3

+

Asymmetric mode(4)

1111

Stick Plot of Rotational StructureNDND22HH22

++ Antisymmetric mode ( Antisymmetric mode (vv66) )

NDND22HH22++ Symmetric mode( Symmetric mode(11))

NDND33HH++ NH stretch mode( NH stretch mode(11))

NDHNDH33++ Asymmetric stretch mode( Asymmetric stretch mode(44))

1212

Results of NDResults of ND33HH+ + Ion Ion

1313

• Q branch feature of parallel band• Ground state combination difference (GSCD)• Nuclear spin statistic• Some transitions show perturbation

High Resolution Jet-cooled SpectrumHigh Resolution Jet-cooled Spectrum

1414

Boltzmann Plot and Rotational TemperatureBoltzmann Plot and Rotational Temperature

2/( , ) (2 1) (2)

1ln ln ( , )

(2 1) (2)

rotE kTns

ns rot

S C g J K J HL e

Sg J K E

C J HL kT

Expected value 22 K=3 16 K=1, 2 11 K=0

NDND33HH++

1515

Fitting Results:Fitting Results:

B”B” 3.706595(26)3.706595(26)

C”C” 2.90692.9069

D”D”JJ 6.71(25)6.71(25)1010-5-5

D”D”JKJK 6.70(68)6.70(68)1010-5-5

D”D”KK 00

//

1

F(J,K)=BJ(J+1)+[C-B]K2DJJ4 DJKJ(J+1)K2 DKK4

B’B’ 3.65114(76)3.65114(76)

C’C’ 2.90102(48)2.90102(48)

D’D’JJ 2.893(62) 2.893(62) 1010-3-3

D’D’JKJK 2.360(14) 2.360(14) 1010-3-3

D’D’KK 7.15(92) 7.15(92) 101044

00 3316.8347(19)3316.8347(19)

1616

Results of NDResults of ND22HH22+ + Ion Ion

c

b

1717

Jet-cooled Spectrum of v6 Mode

NDND22HH22++

1818

Jet-cooled Spectrum of v1 Mode

NDND22HH22++

1919

Band Intensity for vBand Intensity for v66 and v and v11 Modes Modes

2/

2

(2 1)

ln ln(2 1)

JK Ka c

JK Ka c

JK Ka c a c

E kTins i

i

JK Ki

ns

S C g J e HL

S EC

g J HL kT

Bond-dipole model

I(Qantisym) / I(Qsym) = 2/1

2020

GroundGround 11 mode mode 66 mode modeAA 4.85675(5)4.85675(5) 4.80782(4)4.80782(4) 4.82922(4)4.82922(4)BB 3.96819(4)3.96819(4) 3.94615(6)3.94615(6) 3.94784(3)3.94784(3)CC 3.44667(5)3.44667(5) 3.44190(5)3.44190(5) 3.43182(5)3.43182(5)

JJ 101066 6.5(1.6)6.5(1.6) 13.0(1.2)13.0(1.2) 4.2(1.5)4.2(1.5)KK 101066 5.3(9.4)5.3(9.4) 20.7(12.4)20.7(12.4) 1.5(7.4)1.5(7.4)JJ 101055 6.5(3)6.5(3) 6.3(2)6.3(2) 6.2(2)6.2(2)JKJK 101055 4.8(9)4.8(9) 4.3(8)4.3(8) 3.6(9)3.6(9)KK 101044 1.18(9)1.18(9) 0.90(6)0.90(6) 1.34(6)1.34(6)

vv00 3297.5439(1)3297.5439(1) 3337.9050(1)3337.9050(1)

Fitting Results of NDFitting Results of ND22HH22++ Ion Ion

A-reduced Hamiltonian

( ) 2 2 2 4 2 2 4

2 2 2 2 2 2 2 2 22 ( ) ( ) ( )

Aeff a b c J JK a K a

J b c K a b c b c a

H AJ BJ CJ J J J J

J J J J J J J J J

~ 40 cm-1

2121

Theoretical CalculationTheoretical Calculation

NDND22HH22++ NDND33HH++

Exp.Exp. Cal.Cal. Exp.Exp. Cal.Cal. 11 3297.5439(1)3297.5439(1) 3297.63297.6 -0.056-0.056 3316.834(1)3316.834(1) 3311.43311.4 5.4345.43422

33

44

55

66 3337.9050(1)3337.9050(1) 3333.43333.4 4.5054.50577

88

99

Chem. Phys. Lett, 258, 129(1996)

2222

Jet-cooled Spectrum of NDHJet-cooled Spectrum of NDH33+ + ion ion

NDH3+

2323

Q branch of 4(E) Mode

T. Nakanaga, T. Amano , Can. J. Phys., 64, 1356 (1986)

Vibration angular momentuml-type doubling

SummarySummary• High resolution of jet-cooled spectra of NH stretch modes of

ND3H+(1) and ND2H2+(1,6) assigned for the first time

• Band origins and band types are determined

• Band intensity of v1 and v6 mode and bond dipole physical model

• Fingerprint in astronomy

N2H7+H5O2

+(Zundel or Eigen) ?

Further work will be extended into hydrogen bonded complexes

2525

AcknowledgementAcknowledgement

David J. NesbittDavid J. NesbittGrant BuckinghamGrant BuckinghamMelanie Roberts (Stony Brook)Melanie Roberts (Stony Brook)

Thank you for your attentionThank you for your attention

JILAJILA