The B 2 Σ - - X 2 Π 3/2 Transition of AuO Leah O’Brien and Bradley Borchert Southern Illinois University Edwardsville Jim O'Brien, S. Shaji, and Adam Farquhar University of Missouri - St. Louis

Recent Work on AuO Photoelectron Spectroscopy of AuO - and AuOPhotoelectron Spectroscopy of AuO - and AuO Ionization potential of AuO - (EA of AuO)Ionization potential of AuO - (EA of AuO) Spin-orbit splitting in X 2 Π 3/2 state of AuOSpin-orbit splitting in X 2 Π 3/2 state of AuO Vibrational frequenciesVibrational frequencies Ichino et al., J. Chem. Phys. A 108 (2004) Ichino et al., J. Chem. Phys. A 108 (2004) Microwave Spectroscopy of AuO X 2 Π 3/2Microwave Spectroscopy of AuO X 2 Π 3/2 Precise constants for v=0,1 of X 2 Π 3/2 statePrecise constants for v=0,1 of X 2 Π 3/2 state Okabayashi et al., Chem. Phys. Lett. 403 (2005) Okabayashi et al., Chem. Phys. Lett. 403 (2005) Electronic Spectroscopy of AuO a 4 Σ - 3/2 – X 2 Π 3/2Electronic Spectroscopy of AuO a 4 Σ - 3/2 – X 2 Π 3/2 (0,1) and (1,2) bands near and cm -1(0,1) and (1,2) bands near and cm -1 Includes ab initio calculation by B. RoosIncludes ab initio calculation by B. Roos O’Brien et al., J. Chem. Phys. A 110 (2006) O’Brien et al., J. Chem. Phys. A 110 (2006) Electronic Spectroscopy of AuO b 4 Π 3/2 – X 2 Π 3/2Electronic Spectroscopy of AuO b 4 Π 3/2 – X 2 Π 3/2 Previous talk by Jim O’BrienPrevious talk by Jim O’Brien Shaji et al., J. Mol. Spectrosc. 243 (2007) 37–42Shaji et al., J. Mol. Spectrosc. 243 (2007) 37–42

Experimental Method Hollow cathode sourceHollow cathode source 2-inch gold-lined cathode2-inch gold-lined cathode Helium (3-4 torr) + oxygen (5-8%)Helium (3-4 torr) + oxygen (5-8%) Current set at 0.5 AmpCurrent set at 0.5 Amp Used Intracavity Laser Absorption SpectroscopyUsed Intracavity Laser Absorption Spectroscopy U Missouri – St Louis labU Missouri – St Louis lab Pyrromethene 556 dyePyrromethene 556 dye Recorded cm -1 regionRecorded cm -1 region 6 cm -1 per scan6 cm -1 per scan Record background with discharge off for each scanRecord background with discharge off for each scan Divide AuO spectrum by background spectrum to normalizeDivide AuO spectrum by background spectrum to normalize

AuO Spectrum

AuO Spectrum Recorded Numerous bands identified in cm -1 regionNumerous bands identified in cm -1 region Several vibrational progressions that connect with v=0 of the ground stateSeveral vibrational progressions that connect with v=0 of the ground state Previous workPrevious work 17153, 17552, 17933, and cm -1 bands17153, 17552, 17933, and cm -1 bands Assigned as the (0,0), (1,0), (2,0), (3,0) and (4,0) bands of a new b 4 Π 3/2 – X 2 Π 3/2 transition of AuOAssigned as the (0,0), (1,0), (2,0), (3,0) and (4,0) bands of a new b 4 Π 3/2 – X 2 Π 3/2 transition of AuO This workThis work 16900, 17329, and cm -1 bands16900, 17329, and cm -1 bands Identified as new progressionIdentified as new progression

16900, 17329, and cm -1 bands cm -1 band analyzed first17329 cm -1 band analyzed first 9 branches were identified9 branches were identified 3 sets of P,Q, and R branches were identified that all connected with v=0 of the ground state (confirmed using microwave constants for ground state)3 sets of P,Q, and R branches were identified that all connected with v=0 of the ground state (confirmed using microwave constants for ground state) 6 branches (2 P, 2 Q, and 2 R branches) can be combined using a 2 Σ Hamiltonian for the excited state6 branches (2 P, 2 Q, and 2 R branches) can be combined using a 2 Σ Hamiltonian for the excited state Remaining 3 branches have bandhead near cm -1, so are not connectedRemaining 3 branches have bandhead near cm -1, so are not connected

AuO Spectrum from ILS

J”PePfPf Q ef Q fe ReRe RfRf ObsO-CObsO-CObsO-CObsO-CObsO-CObsO-C

Fitting the cm -1 band Fit as 2 Σ - X 2 Π 3/2 transitionFit as 2 Σ - X 2 Π 3/2 transition In the X 2 Π 3/2 state, the λ-doubling is not resolved, so we can not assign e/f labels to the branchesIn the X 2 Π 3/2 state, the λ-doubling is not resolved, so we can not assign e/f labels to the branches Transition was fit two ways, based on the two possible e/f assignmentsTransition was fit two ways, based on the two possible e/f assignments Two sets of parameters for the excited state were determinedTwo sets of parameters for the excited state were determined

Excited State Parameters for band of AuO, 2 Σ Main difference is spin-rotation parameter for 2 ΣMain difference is spin-rotation parameter for 2 Σ Fit 1 Value EvEv (47) BvBv (71) DvDv (20) x HvHv (20) x γ (87) γDγD (74) x γHγH (25) x Fit 2Value EvEv (48) BvBv (62) DvDv (18) x 10-4 HvHv (20) x γ0.1128(87) γDγD (80) x γHγH (23) x 10 -5

Excited State Assignment: A 2 Σ + or B 2 Σ - ? 2Σ-2Σ- 2Σ+2Σ+ Björn Roos

Ab initio Parameters for Excited 2 Σ states (in cm -1 ) A 2 Σ + B 2 Σ - This work TeTeTeTe ~16248* ωeωeωeωe ~440.6* r e (Å) r 3 * = *assuming the cm -1 band is the (1,0) band

Spin-Rotation in B 2 Σ - State Can we predict γ for the B 2 Σ - state?Can we predict γ for the B 2 Σ - state? 2 Π states interact with the 2 Σ states to make spin-rotation splitting 2 Π states interact with the 2 Σ states to make spin-rotation splitting X 2 Π (0 cm -1, A so ~ cm -1 )X 2 Π (0 cm -1, A so ~ cm -1 ) A 2 Σ + (14,000 cm -1 )A 2 Σ + (14,000 cm -1 ) B 2 Σ - (16,600 cm -1 )B 2 Σ - (16,600 cm -1 ) C 2 Π (25,000 cm -1, A so ~ cm -1 )C 2 Π (25,000 cm -1, A so ~ cm -1 ) Oh $#!Γ…Oh $#!Γ…

When the Going Gets Tough, Call Bob Field! Bob says “We have lots of information…”Bob says “We have lots of information…” Spin rotation is either large and negative or small and positiveSpin rotation is either large and negative or small and positive Spin-rotation splitting arises from a cross term between H rot and H so, so the signs of off-diagonal elements of both H rot and H so enter into the predicted value of the spin-rotation constantSpin-rotation splitting arises from a cross term between H rot and H so, so the signs of off-diagonal elements of both H rot and H so enter into the predicted value of the spin-rotation constant All we need is electronic configurations for 2 Π and 2 Σ states (from Björn Roos)All we need is electronic configurations for 2 Π and 2 Σ states (from Björn Roos)

Au AuO X 2 Π O 5d 6s 2p 5dπ 1σ1σ 2σ2σ 3σ3σ 5dδ 2pπ C 2ΠC 2Π A 2Σ+A 2Σ+ B 2Σ-B 2Σ-

Spin-Rotation for B 2 Σ - In ProgressIn Progress (THANKS BOB!)(THANKS BOB!)

16900, 17329, and cm -1 bands Analysis of the and cm -1 bands are completedAnalysis of the and cm -1 bands are completed Analysis of the band is underwayAnalysis of the band is underway Spectra of the and cm -1 bands will be recorded Summer 2007Spectra of the and cm -1 bands will be recorded Summer 2007 The vibrational assignments are not known: at this time, we are simply assuming that the cm -1 band is the (1,0) bandThe vibrational assignments are not known: at this time, we are simply assuming that the cm -1 band is the (1,0) band Roughly based on the calculated separation between the b 4 Π 3/2 and B 2 Σ - statesRoughly based on the calculated separation between the b 4 Π 3/2 and B 2 Σ - states

AuO Spectrum from ILS

Summary Accomplished:Accomplished: Identified the B 2 Σ - - X 2 Π 3/2 transition in AuOIdentified the B 2 Σ - - X 2 Π 3/2 transition in AuO Analyzed the and cm -1 bandsAnalyzed the and cm -1 bands To Do:To Do: Estimate spin-rotation parameter for B 2 Σ - stateEstimate spin-rotation parameter for B 2 Σ - state 16900, and cm -1 bands16900, and cm -1 bands Dunham-type fitDunham-type fit

Acknowledgements S. Shaji, UMSL post-doctoral fellowS. Shaji, UMSL post-doctoral fellow Brad Borchert, SIUE undergraduate studentBrad Borchert, SIUE undergraduate student Adam Farquhar, Westminster HS (St. Louis)Adam Farquhar, Westminster HS (St. Louis) Summer 2006 research student at UMSL with STARS program for gifted studentsSummer 2006 research student at UMSL with STARS program for gifted students Bob Field (MIT)Bob Field (MIT) Björn Roos (Lund, Sweden)Björn Roos (Lund, Sweden) FundingFunding NSF (Leah and Jim)NSF (Leah and Jim) PRF (Leah)PRF (Leah) Thank you for your attention!Thank you for your attention!