Detection of the Magnetic Dipole Allowed Origin Band

Detection of the Magnetic Dipole. Allowed Origin Band of the A-X Transition of the Nitrate Radical NO 3 7000 7050 7100 Kana Takematsu, Nathan Eddingsaas, and Mitchio Okumura, California Institute of Technology; John Stanton, University of Texas, Austin. Ohio State 64 th International Symposium on Molecular Spectroscopy, June 22 -26, 2009

Jahn Teller (JT) Active The Nitrate Radical NO 3 JT Active B 2 E' A 2 E″ X 2 A'2

Jahn Teller (JT) Active The Nitrate Radical NO 3 B 2 E' Pseudo-JT (PJT) coupling JT Active A 2 E″ PJT coupling X 2 A'2

Strong but complicated X-B spectrum Carter, et. al. CPL 1996 (0. 05 cm-1 stepsize) n More info: Shunji Kasahara (Kobe Univ. ), et. al. TJ 07 Ultrahigh-resolution spectroscopy of the B 2 E”-X 2 A 2 ’ transition of NO 3 radical

Weak but structured and manageable A-X Spectrum Deev, JCP 2005

The Electronic States of 15089 NO cm 3 -1 Three low lying electronic states: § X State D 3 h symmetry § X-B Transition Very strong and ideal for detection Broad due to vibronic interactions (~2 e. V) B 2 E' very strong σ≈2 x 10 -17 cm 2 7060 cm-1 (~1 e. V) D 3 h A 2 E″ X 2 A'2

The Electronic States of 15089 NO cm 3 Three low lying electronic states: -1 (~2 e. V) § X State D 3 h symmetry § X-B Transition Very strong and ideal for detection Broad due to vibronic interactions § B 2 E' very strong σ≈2 x 10 -17 cm 2 7060 cm-1 (~1 e. V) A 2 E″ X-A Transition Weak as electric-dipole forbidden D 3 h X 2 A'2

§ X State D 3 h symmetry § X-B Transition The Electronic States of 15089 NO cm 3 Very strong and ideal for detection Broad due to vibronic interactions § § -1 (~2 e. V) X-A Transition very strong electric-dipole forbidden σ≈2 x 10 -17 cm 2 Weak as Vibronic bands can be rotationally resolved 7060 cm-1 Nonadiabatic effects Jahn Teller (JT) effect in A 2 E″ and B 2 E' (~1 e. V) Pseudo-JT coupling among X, A, and B states B 2 E' weak σ≈10 -20 cm 2 A 2 E″ forbidden D 3 h X 2 A'2 More info: Marilyn Jacox (NIST), et. al. TF 12 The A-X and B-X absorptions of NO 3 trapped in solid neon n

Electric dipole-allowed A-X vibronic bands: The Herzberg-Teller effect Intensity borrowing via vibronic coupling

The Herzberg-Teller effect: HABPJT(1) B 2 E' band Perpendicular Transition n 2(a 2”) A 2 E″ X 2 A' 2 cm-1 Borrow intensity from strong X-B transition via weak linear PJT coupling between A and B

The Herzberg-Teller effect: HXB PJT(1) B 2 E' band Parallel Transition n 4(e’) A 2 E″ X 2 A'2 cm-1 Borrow intensity from weak A-B transition via strong linear PJT coupling between X-B

CRD spectrum of A-X Transition of NO 3 Blue: parallel Pink: perpendicular Deev, JCP 2005

à State: static or dynamic JT distortion? n Adiabatic model of NO 3 1. 28 Å 1. 20 Å Pseudorotation barrier 113° 130° Bend and stretch changes 1. 41 Å C 2 v MINIMUM 2 B 1 2000 -3000 cm-1 below conical intersection C 2 v TRANSITION STATE 2 A 2 +800 -1000 cm-1 **Eisfeld, Morokuma. JCP 2001: MRCI

à State: static or dynamic JT distortion? n Adiabatic model of NO 3 1. 28 Å 1. 20 Å Pseudorotation barrier 113° 130° Bend and stretch changes 1. 41 Å C 2 v MINIMUM 2 B 1 2000 -3000 cm-1 below conical intersection n C 2 v TRANSITION STATE 2 A 2 +800 -1000 cm-1 **Eisfeld, Morokuma. JCP 2001: MRCI Need non-adiabatic model of NO 3 to fully explain A state John Stanton: On the vibronic level structure in the NO 3 radical. I. The ground electronic state, JCP 2007 On the vibronic level structure in the NO 3 radical Part III. Observation of intensity borrowing via ground state mixing, PCCP 2009

Previous Experiments on the à State § Weaver, Chem. Phys. 1991: Low resolution anion photoelectron spectrum

Previous Experiments on the à State § § Weaver, Chem. Phys. 1991: Low resolution anion photoelectron spectrum Hirota, et. al. , JCP 1997: High resolution spectrum of the n 4 band D 3 h

Previous Experiments on the à State § § § Weaver, Chem. Phys. 1991: Low resolution anion photoelectron spectrum Hirota, et. al. , JCP 1997: High resolution spectrum of the n 4 band D 3 h Deev, et. al. , JCP 2005: CRD spectrum D 3 h *simulation from Deev thesis

Previous Experiments on the à State § § C 2 v § Weaver, Chem. Phys. 1991: Low resolution anion photoelectron spectrum Hirota, et. al. , JCP 1997: High resolution spectrum of the n 4 band D 3 h Deev, et. al. , JCP 2005: CRD spectrum *simulation from Deev thesis

Previous experiments on the à State § § § Weaver, Chem. Phys. 1991: Low resolution anion photoelectron spectrum Hirota, et. al. , JCP 1997: High resolution spectrum of the n 4 band D 3 h Deev, et. al. , JCP 2005: CRD spectrum Mode-dependent symmetry D 3 h C 2 v Would like to probe the zero point of the A state *simulation from Deev thesis

Position of magnetic dipole-allowed origin? n n n PES (Weaver): 7000 ± 110 cm-1 Absorption spectrum of n 4 band (Hirota): 7068 ± 8 cm-1 CRDS of –n 4 band (Deev): 7064 cm-1 *from JCP 2005

CRD spectrum of A-X transition of NO 3 Room Temperature Scan (interference from water lines) Nitric acid 1/τ Origin? cm-1 (0. 4 cm-1 stepsize)

CRD spectrum of A-X transition of NO 3 Hot Temperature Scan (80°C): less water, more NO 3 Intensity=Room T Intensity x 4 1/τ Origin!! cm-1 (0. 4 cm-1 stepsize) More info on hot bands: Kana Takematsu (Caltech), et. al. WJ 11 The Jahn-Teller Effect in the A State of the Nitrate radical NO 3 n

Origin band 1/τ 45000 25000 7000 7050 cm-1 7100 (0. 2 cm-1 stepsize)

Origin band Position: In agreement with previous experiments 7067 cm-1 1/τ 45000 25000 7000 7050 cm-1 7100 (0. 2 cm-1 stepsize)

Origin band 45000 1/τ 7067 cm-1 25000 7000 7050 cm-1 7100 (0. 2 cm-1 stepsize)

Simulation of magnetic dipole-allowed transition PGopher Arbitrary units Origin = 7067 cm-1 7010 7030 7050 7070 cm-1 7090 7110

Rotational contours of electric dipole allowed transitions Parallel Transition Perpendicular Transition

Rotational contour of magnetic dipole allowed transition PGopher Arbitrary units Origin = 7067 cm-1 7010 7030 7050 7070 cm-1 7090 7110

Compare spectrum and simulation § Pink_spectrum § Black_PGopher cm-1

Summary and future work n n Observed the magnetic dipole-allowed origin of the A-X NO 3 transition via cavity ringdown spectroscopy Band origin: 7067 cm-1 n n Rotational contour shows pronounced Q branch

Summary and future work n n Observed the magnetic dipole-allowed origin of the A-X NO 3 transition via cavity ringdown spectroscopy Band origin: 7067 cm-1 n n Rotational contour shows pronounced Q branch n Improve rotational contour simulation of origin band Nonadiabatic ab initio model: verify position and intensity Better understand the JT strength in the A state Use origin position to analyze other CRDS data n n n

Acknowledgements & related talks n n n Colin Western (PGopher) Okumura group NASA UARP & NSF ($$) EPA STAR Graduate Fellowship (Kana) Camille and Henry Dreyfus Postdoctoral Fellowship (Nathan) Related Talks: n n n Kana Takematsu (Caltech), et. al. WJ 11 The Jahn-Teller Effect in the A State of the Nitrate radical NO 3 Ming-Wei Chen (OSU), et. al. TF 13 Jet-Cooled Laser Spectroscopy of a Jahn-Teller active molecule: The Nitrate Radical Nathan Eddingsaas (Caltech), et. al. TI 01 The A-X Absorption Spectrum of 2 -nitrooxybutyl peroxy radical