1. The electronic spectrum and molecular structure of HAsO, the arsenic analog of HNO Robert Grimminger and Dennis J. Clouthier Department of Chemistry, University of Kentucky, Lexington KY

2. Reasons to study HAsO Arsine is used in semiconductor processes (n-type doping and III-V) Add to the information available for arsenic containing radicals studied by Clouthier group: AsH 2, H 2 AsO, AsC and AsC 2 Heavy atom analog of HNO – As predicted by Walsh diagrams, the HNO bond angle increases from ground to excited state – However, the bond angle of HPO decreases from ground to excited state

3. Molecular orbitals of HAsO

4. Production of jet-cooled radicals Precursor gas mix: 3% AsH 3 + 3% CO 2 in Ar Precursor gas mix: 3% AsD 3 + 3% CO 2 in Ar OSHA limit: 50 ppb

5. LIF spectra Calc. = B3LYP/aug-cc-pV(5+d)Z ν 2 = HAsO bend ν 3 = AsO stretch Obs. isotope shift = 39.1 cm -1 Calc. isotope shift = 28.3 cm -1 Constant HAsODAsO obs.calc.obs.calc. 1010 ···2042···1454 2020 604.61(52)562445.97(28)421 3030 648.94(72)684638.58(65)667 x 22 0 -5.28(10)··· x 33 0 -3.06(26)-3.96(14) x 23 0 ···-2.32(16)

6. Analysis of emission spectra Calc. = B3LYP/aug-cc-pV(5+d)Z Constant (cm -1 ) HAsODAsO obs.calc.obs.calc. 1010 ···1970···1405 2020 836.98(52)849631.78(92)627 3030 944.4(1.2)974929.47(70)965 x 22 0 -3.31(16)-4.75(54) x 33 0 -7.45(61)-4.51(28) x 23 0 -7.71(31)-5.53(49) ν 2 = HAsO bend ν 3 = AsO stretch

7. High-resolution of HAsO 0 0 band StateConstant HAsO DAsO X̃ 1 A A7.27122 6 (76)3.73722 3 (35) B0.474287 4 (93)0.468878 2 (91) C0.444221 9 (84)0.415355 9 (84) Ã 1 A  A7.0688 9 (41)3.59794 1 (26) B0.416180 6 (89)0.414566 2 (86) C0.391788(87)0.370329 8 (85) T0T0 15316.6740(23)15348.8923(21) 0

8. Excellent fit, but…

9. Axis-tilting Inertial axes fixed by geometry In a fixed frame of reference, the sets of inertial axes for the two states are rotated from each other The tilting causes extra branches to appear in the electronic spectra of low symmetry molecules a″a″ θ a′ b″b″ b′

10. ΔK a = even ΔK c = even Axis-tilting simulation

11. Geometry of HAsO 1.6342(5) Å [1.631] 1.576(3) Å [1.572] 101.5(4)° [101.5] 93.1(10)° [91.7] 1.7509(9) Å [1.745] 1.569(4) Å [1.545] Ground stateExcited state Values in brackets are b3lyp/aug-cc-pV(5+d)Z

12. Change in geometry of HNO analogs -8.4° -7.2° +6.9°

13. HAB Walsh diagram a˝a˝ a˝a˝ a´a´ a´a´ a´a´ a´a´ a´a´ π π σ σ σ

14. HAsO Walsh diagrams Ground stateExcited state Orbital energies at B3LYP/aug-cc-pVTZ

15. Conclusions Detected spectra of the HAsO free radical for the first time Analyzed LIF and SVL emission spectra Determined molecular geometry of both states HAsO is another HNO analog that doesn’t follow Walsh’s rules

16. +17.4°