PFI-ZEKE photoelectron and high resolution photoionization spectra of ND₃with MQDT simulations

Abstract

The rotationally resolved PFI-ZEKE (pulsed-field ionization zero-kinetic energy) photoelectron spectrum of ND 3 has been recorded at the v 2 + = 0, 1 and 2 thresholds, by single-photon VUV excitation from the ground-state. An assignment of the 2 2 A X     1 1 A X  spectrum is presented, allowing a determination of the adiabatic ionization potential of ND 3 (82261.7(15) cm-1) and of the rotational constants and positions of the v 2 + = 0, 1 and 2 vibrational levels of the ND 3 + ion. These parameters are used in a multichannel quantum defect theory (MQDT) simulation of the highresolution photoionization spectrum in the range 82100-83300 cm-1 [(R. Seiler et al., J. Chem. Phys. 118 10024 (2003)]. A good simulation and an assignment of around 80% of the lines of the ND 3 photoionization spectrum are achieved, verifying the validity of the molecular constants derived from the PFI-ZEKE photoelectron spectrum and also the quantum defect parameters derived from ab initio calculations.

State-to-state resolved differential cross sections for rotationally inelastic scattering of ND3with He

“…[39][40][41] One consequence of symmetry and nuclear spin constraints is that only transitions originating from the lower (+) inversion component of the ground state appear in bands in which the final ߥ ଶ is even, whereas only transitions from the upper (−) inversion 35 component appear in bands with final ߥ ଶ odd. Therefore, two vibrational transitions must be excited to probe all individual rotational states.…”

“…9 Fully deuterated ammonia, ND 3 , has been observed in prestellar cores. 10 Cheung et al 11 noted that the 35 observed NH 3 emission intensities from interstellar sources do not correspond to a single rotational temperature. In addition, the inversion transition was detected for the rotational level j k = 11 9 , 12 which should not be populated at interstellar temperatures of 10-300 K, and the j k = 3 3 inversion transition has been predicted 13 40 and observed 14 to exhibit maser activity.…”

“…However, the laser bandwidth was ~0.3 cm -1 and the ~4.5 mJ energy per pulse of the laser power broadened the transitions 35 sufficiently that Doppler scanning was unnecessary.…”

“…The radius of the recorded ion image is then directly proportional to the CM-55 frame speed of the ions at their point of formation by REMPI. For the ionization schemes employed here, the recoil of the electron from the ion (deriving from the excess energy of three UV photons above the 10.08 eV 34,35 ionization energy of ND 3 ) can impart up to 20 ms -1 to the ND 3 + corresponding to an ~3 pixel 60 blurring of …”

“…25 At this level of resolution of the dynamics of a scattering process, rigorous comparisons can be drawn between experimental measurements and the outcomes of quantum mechanical (QM) scattering calculations. Such comparisons provide stringent tests of the accuracy of ab initio 35 for the collisional processes of interest. Although there is a significant body of work on inelastic scattering of diatomic molecules, such detailed experimental and computational investigations for scattering of polyatomic molecules remain relatively rare.…”