Photoelectron spectrum ammonia

The photoelectron spectrum of the ammonia molecule is consistent with the molecular orbital conclusions there are three ionization energies at... 

As a freely ionic, monomeric species, the silyl anion may undergo pyramidal inversion about the silicon center (equation 1). For the parent system H3Si , Nimlos and Ellison have obtained quantitative information about the inversion barrier from the photoelectron spectrum in the gas phase2. The photoelectron spectrum could be simulated by a model of the vibrational frequency as a linear oscillator perturbed by a Gaussian barrier. The out-of-plane angle (the deviation of one H from the plane defined by Si and the other two Hs) was found to be 32 2° and the barrier to inversion 9000 2000 cm 1 (26 6 kcal mol-1). This is the only experimental measurement to date of the barrier to inversion about trivalent, negative silicon. The anion was produced by reaction of silane (SiH4) with ammonia, and the photoelectron spectrum of the m/z 31 peak was then recorded. 

Fig. 11. The charge-exchange mass spectrum of ammonia as a function of energy/ together with its photoelectron spectrum. ...

The electron affinity A = 0.771 0.005 was determined from a high-resolution (5 to 25 meV) photoelectron spectrum of NH2 [1]. A = 0.779 0.037 was obtained from a photoelectron spectrum at lower resolution [2]. Photodetachment-threshold measurements gave A = 0.744 0.022 [3] and 0.76 0.04 [4]. A = 0.76 0.14 was determined from pulsed ICR studies of ion-molecule reactions in ammonia [5]. A considerably higher value, A=1.2, resulted from applying the magnetron method [6]. 

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