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+.

Ab initio potential energy surface, electric-dipole moment, polarizability tensor, and theoretical rovibrational spectra in the electronic ground state of

“…(15) obey the following permutation rules: Table 3 ATZfc polarizability tensor parameters a a ð0Þ ijk... in the MB representation for the electronic ground state of 14 …”

“…We use here the related unit Å 3 = 10 À24 cm 3 . Table 4 ATZfc polarizability tensor parameters a c ð0Þ ijk... in the MB representation for the electronic ground state of 14 We have determined the values of the expansion parameters in Eq. (15), which we take to fourth-order, in a leastsquares fitting to the 3 Â 2281 ab initio dipole moment projections l Á e j ðj ¼ 1; 2; 3Þ.…”

“…m 2 þ m 3 [1][2][3]. At low resolution, the 14 NH þ 3 ion has been studied by photoelectron and photoionization spectroscopy [4][5][6][7][8][9][10][11][12][13][14][15]. Further, the infrared spectrum of NH þ 3 , trapped in a solid neon matrix, has been recorded [16].…”

Franck–Condon factors in curvilinear coordinates: the photoelectron spectrum of ammonia

“…[37] c Ref. [43] Although the main features of the experimental spectrum are reproduced by FC computations, the predicted intensity distribution is significantly different from the observed one. The maximum peak height occurs for the 5 0 0 transition, but the 6 0 0 one exhibits a significantly lower intensity than the 5 0 0 transition.…”

“…Analytical integrals have been used [15,40,41]. The computed energies of the vibrational states are reported in Table 5 together with the available experimental values [37,42,43]. Energies are predicted with reasonable accuracy by both the simple P1 potential of Table 3 and by the more accurate potential of Table 4; the latter one gives a significant improvement only for states with high quantum numbers on the m 2 mode.…”