Line Shapes and dynamics of dangling Line Shapes and dynamics of dangling OD stretch at the air-water interface studied OD stretch at the air-water interface studied by the heterodyne detected sum frequency generation (HD-SFG) spectroscopy Champika N. Weeraman  s (2) E(2)E(2) E(1+2)E(1+2) E(1)E(1) LO

Orientation and dynamics of water aerosols vesicles Bio-membrane Bulk water ? Water interface?

R OH···O (Å) OH (cm -1 ) Bulk water Air/water Weaker H-bonds Stronger H-bonds Du, Q.; Superfine, R.; Freysz, E.; Shen, Y.R. Phys. Rev. Lett. 1993, 70, 2313 Du, Q.; Freysz, E.; Shen, Y.R. Science 1994, 264, 826 Scatena, L.F.; Brown, M.G.; Richmond, G.L. Science 2001, 292, 908 Richmond, G.L. Chem. Rev. 2002, 102, 2693 Frequency-domain SFG: ‘Ice-like’ ‘Water-like’ Free-OH Hydrogen bond network at water interface

SFG spectra: air-water interface Wei, X.; Superfine, Shen, Y.R. Phys. Rev. Lett. 2001, 86, 4799 Richmond, G. L. et.al. J.Phys. Chem. B. 2003, 107, 546 Different polarization combinationIsotopic dilution (SSP polarization)

Hydrogen bond network at water interface H-bond dynamics at water surfaces Free OH SFG line shapes (SSP, SPS, PPP) Vibrational energy transfer Interference in spectra in spectra Isotopic dilution Method :HD-SFG Orientation dynamics dynamics

Experiment Isotopic dilution System: Free OD at air-water interface (~2730cm -1 ) Goals: ► Reorientational time scales from SFG line shapes ► Isotopic dilution effect on H-bond dynamics and intermolecular energy transfer Reorientation time of bulk water ~0.7ps to ~4ps Nienhuys, H.; Santana, R.A.V; Bakker, H. J.; J. Chem. Phys, 2000, 112, 8487 Laenen, R.; Rauscher, C.; Lamberean, A. J. Phys. Chem B,2001, 102, 9304

SFG vis IR Sample Monochromator CCD LO LO KNbO 3 Heterodyne detected SFG τ Intensity of Heterodyne detected SFG signal Stiopkin, I. V.; Jayathilake, H. D.; Bordenyuk, A. N.; Benderskii, A.V.; JACS (2008), 130(7) Spectral Interferometry N Homodyne (SFG) Heterodyne I het I homo

Heterodyning SFG Signal of D 2 O Heterodyne detected Spectrum of D 2 O VIS IR SFG LO Cross term (-) Spectrum of local oscillator (LO)

1.Raw Interferograms Data Processing 2. IFFT (Time domain spectrum) 3. FFT (Frequency domain spectrum) Apply window (Filter out error in subtraction of LO ) NR Res.

SFG spectra of free-OD at air-water interface SSP PPP 12.5% D 2 O 100% D 2 O 50% D 2 O 100% D 2 O 50% D 2 O 12.5% D 2 O

Data processing D 2 O 100% D 2 O 0% D 2 O 100%-0%

SFG spectra of free-OD at air-water interface SSPPPPSPS Γ=26 cm -1 Γ=18 cm -1 Γ=19 cm -1

Orientational Dynamics in SFG Line Shapes z SFG S P y vis S P S P IR P SS x S P P SS S visIRSFG PPPPPP visIRSFG SSPSSP visIRSFG SPSSPS Frequency-domain SFG Γ = Γ energy tran. + Γ vib. + Γ rotational Γ= Γ energy tran. + Γ vib. + Γ rotational Orientational molecular dynamics at air/water interfaces studied with vibrational SFG spectroscopy Igor V. Stiopkin, Achani K. Yatawara, Himali D. Jayathilake, Champika N. Weeraman and Alexander V. Benderskii Department of Chemistry, Wayne State University, Detroit, MI

SFG spectra of free-OD at air-water interface SSPPPPSPS Γ=26 cm -1 Γ=18 cm -1 Γ=19 cm -1 Γ SSP = 19 cm -1 Γ SPS = 26 cm -1 Γ rot ~ 7 cm -1 τ rot ~ 0.6 ps

Forster resonance energy transfer (FRET) Higher concentration Lower concentration

SFG spectra of free-OD at air-water interface SSPPPP 0.77 mf H 2 O 0.02 mf D 2 O 0.21 mf HOD 0.25 mf H 2 O 0.25 mf D 2 O 0.5 mf HOD 0.0 mf H 2 O 1.0 mf D 2 O 0.0 mf HOD Isotopic dilution Γ=16 cm -1 Γ=19 cm -1 Γ=15 cm -1 Γ=18 cm -1 Γ=14 cm -1 Γ=17 cm -1

Conclusions ► HD-SFG technique allows to extract true line width of the free OD stretch transition by subtracting non-resonance free OD stretch transition by subtracting non-resonance background signal ► True line width of SSP and PPP spectra are different from SPS which gives the in-plane re-orienation time of D 2 O at air-water interface (~0.6 ps) of D 2 O at air-water interface (~0.6 ps) ► Narrowing of free OD line width at lower concentration could be due to Forster energy transfer

Acknowledgements WSU start-up grant WSU research grant WSU-IMR NSF CAREER Grant No Funding Benderskii group US AFOSR

Heterodyne detected sum frequency generation (HD-SFG) Stiopkin, I. V.; Jayathilake, H. D.; Bordenyuk, A. N.; Benderskii, A.V.. JACS (2008), 130(7)

Time-domain SFG-FID Frequency-domain SFG SSPSSP visIRSFG S z x S y vis IR P S vis IR PP S Γ=10.7 ± 1 cm -1 Orientational Dynamics in SFG Line Shapes

SPSSPS visIRSFG S z x S y vis IR S P vis IR SS P Γ=15 ± 1 cm -1 Time-domain SFG-FID Frequency-domain SFG Orientational Dynamics in SFG Line Shapes

Time-domain SFG-FID Frequency-domain SFG Γ SSP = 10.7 ± 1 cm -1 Γ SPS = 15 ± 1 cm -1 Γ rot ~ 4 cm -1 Γ rot ~ 4 ± 1 cm -1 τ rot ~ 1.1 ± 0.3 ps SFG intensity (Norm) IR- vis delay (fs) SFG-FID intensity (Norm) IR- vis delay (fs)

Free OH: Orientation and dynamics at the interface ► Orientation of water molecule within the vibrational relaxation Rapid motion limit: The molecular orientation fluctuate very rapidly around the average orientation within the time scale vibrational Relaxation time (1/Γ q ) Slow motion limit: Molecular orientation fluctuate very slowly than the vibrational Relaxation time (1/Γ q ) Free OD: Experimental A q,eff (SSP) :A q,eff (PPP) :A q,eff (SPS) is better agree with The rapid motion limit and maximum orientation angle ( θ M ) is 51º. Wei, X.; Superfine, Shen, Y.R. Phys. Rev. Lett. 2001, 86, 4799 θMθM

Richmond, G. L. et.al. J.Phys. Chem. B. 2003, 107, 546 ► Line shape of dangling OH at lower concentration Free OH line gets border as the concentration of D 2 O in the solution increases because of two unresolved free OH peaks (one from HOD and one from H 2 O) Free OH: Orientation and dynamics at the interface

Visible IR Time0 E field Frequency SFG Signal Frequency SFG Signal Frequency SFG Signal Visible IR Time0 E field Frequency SFG Signal Frequency SFG Signal Frequency SFG Signal IR-Vis time delay

Sum Frequency Generation: Time Domain vis IR  |v=0  |v=1  IR vis SFG  I SFG (  )   vis t0  IR t P (1) (t) SFG-FID (Free Induction Decay) Guyot-Sionnest, P. Phys. Rev. Lett. 1991, 66, Owrutsky, Culver, Li, Kim, Sarisky, Yeganeh, Yodh, Hochstrasser J. Chem. Phys. 1992, 97, Molecular response function

Sum-frequency generation (SFG) originates from induced polarization Virtual State In media without inversion symmetry  SFG =  IR +  vis S()S() SFG - CCD image Spectrally narrow (temporally long) Vis pulse IR  IR vis  vis Broad-band IR pulse (temporally short) + In media with inversion symmetry Vibrational sum frequency generation (VSFG) ► Broad band VSFG