title: A two-color infrared-vacuum ultraviolet laser pulsed field ionization photoelectron study of NH3.
abstract: We have observed fully rotationally resolved transitions of the photoelectron vibrational bands 2(4), 2(5), 1(1)2(1), and 1(1)2(3) for ammonia cation (NH3+) by two-color infrared (IR)-vacuum ultraviolet (VUV)- pulsed field-ionization photoelectron (PFI-PE) measurements. By preparing an intermediate rovibrational state of neutral NH(3) with a known parity by IR excitation followed by VUV-PFI-PE measurements, we show that the photoelectron parity can be determined unambiguously. The IR-VUV-PFI-PE measurement of the 2(4) band clearly reveals the formation of both even and odd l states for the photoelectrons, where l is the orbital angular momentum quantum number. This observation is consistent with the conclusion that the lack of inversion symmetry for NH3 and NH3+ allows odd/even l mixings, rendering the production of both odd and even l states for the photoelectrons. Evidence is also found, indicating that the photoionization transitions with DeltaK=0 are strongly favored compared to that with DeltaK=3. For the 2(5), 1(1)2(1), and 1(1)2(3) bands, only DeltaK=0 transitions for the production of even l photoelectron states from the J'K'=2(0) rotational level of NH3(nu1=1) are observed. The preferential formation of even l photoelectron states for these vibrational bands is attributed to the fact that the DeltaK=0 transitions for the formation of odd l photoelectron states from the 2(0) rotational level of NH3(nu1=1) are suppressed by the constraint of nuclear-spin statistics. In addition to information obtained on the photoionization dynamics of NH3, this experiment also provides a more precise value of 3232+/-10 cm-1 for the nu1+ (N-H stretch) vibrational frequency of NH3+.
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California 95616, USA.
authors.forename: Mi-Kyung
authors.initials: MK
authors.lastname: Bahng
authors.forename: Xi
authors.initials: X
authors.lastname: Xing
authors.forename: Sun Jong
authors.initials: SJ
authors.lastname: Baek
authors.forename: C Y
authors.initials: CY
authors.lastname: Ng
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D002412:Cations; D002627:Chemistry, Physical / Q000379:methods*; D004583:Electrons; D007259:Infrared Rays; D007477:Ions; D008027:Light; D009584:Nitrogen / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D017785:Photons; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D014618:Vacuum
chemical_list: D002412:Cations; D007477:Ions; D000641:Ammonia; D009584:Nitrogen