Ammonia, inversion spectrum

From its inception, microwave rotational spectroscopy has contributed greatly to our knowledge about classical inorganic compounds. It all began with a low resolution recording of the ammonia inversion spectrum in 1934. The first high resolution microwave spectra were recorded... 

Fig. 17. Energy levels of the rotation-inversion spectrum of ammonia. The quantum numbers (J,K) are given for each level. The heavy arrows indicate the inversion transitions detected in interstellar space and their frequencies in MHz. Thin arrows indicate the rotation-inversion transitions located in the submillimeter wave region. Dashed arrows indicate some collision induced transitions...

The high order one-dimensional approach was first used to consider the inversion spectrum of ammonia along the v2 inversion axis [45]. A similar calculation has been used to examine the influence of solvent on the splitting due to tunneling when a hydrogen atom, for example, can move between two positions of equilibrium [46],... 

The inversion spectrum of the J,K) = 1,1) level of ND3 consists of 72 hyperfine transitions in a frequency interval of about 300 kHz. Due to this spectral congestion, the hyperfine structure could not be resolved in an earlier molecular beam experiment [71]. We have therefore carried out this experiment with a Stark-decelerated molecular beam, using the setup shown schematically in Figure 14.19a. A beam of ammonia molecules is decelerated from 280 m/sec to either 100 or 50 m/sec, and focused into a microwave zone. The microwave zone provides a nearly rectangular... 

LIMIT ON THE TIME VARIATION OF Ji FROM THE INVERSION SPECTRUM OF AMMONIA... 

We see from Equations 16.25 and 16.30 that the inversion frequency and the rotational intervals (Oinv(7i,ATi) — (Oinv(-/2. 2) have different dependencies on p. In principle, this allows one to study time variation of p by comparing different intervals in the inversion spectrum of ammonia. For example, if we compare the rotational interval to the inversion frequency, then Equations 16.25 and 16.30 give... 

Lightman A., Ben-Reuven A. Line mixing by collisions in the far-infrared spectrum of ammonia, J. Chem. Phys. 50, 351-3 (1969) Cross relaxation in the rotational inversion doublets of ammonia in the far infrared, J. Quant. Spectrosc. Radiat. Transfer 12, 449-54 (1972). 

Inversion splitting of the vibrational spectrum of ammonia has been used to create the first molecular microwave amplifier (maser) [86, 87]. The inversion population in the ammonia maser is achieved by transmission of the molecular beam through a non-homogeneous electric field. Ammonia molecules in symmetric and antisymmetric states interact with the electric field in different ways and they are therefore separated in this field. They are then directed to the resonator. 

These early papers, as well as most of the theoretical work on the inversion of ammonia that has been done later, have considered the problem of the solution of the Schrddinger equation for a double-minimum potential function in one dimension and the determination of the parameters of such a potential function from the inversion splittings associated with the V2 bending mode of ammonia Such an approach describes the main features of the ammonia spectrum pertaining to the V2 bending mode but it cannot be used for the interpretation of the effects of inversion on the energy levels involving other vibrational modes or vibration—rotation interactions. 

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. 

B Cloppenburg, K Manczak, H Prockl, HW Schrotter, G Strey. Resolution of K-splitting in the rotation-inversion Raman spectrum of ammonia NH3. Z Naturforsch 34a 1160-1163, 1979. 

Figure 10 is a spectrum of ammonia vapor (plus some residual water vapor) in a 10-cm cell. An evacuated similar cell was in the reference beam. The inversion vibration in ammonia [ ] is characterized by doublet bands which appear in the 138 cm" 119 cm 99 cm and 79 cm regions. The spectrum shows that one of the doublets at 138 cm is resolved. The separation of doublet components in each case is about 1.3 cm" and therefore this band serves to illustrate the resolution of the spectrophotometer in the doublebeam mode (at a place where the filter efficiency curve is less than optimum). The spectrum was scanned very slowly, at 0.7 cm" per minute. 

Fig. 8.3.2 Determination of the ammonia (NH3) abundance in the atmosphere of Jupiter by inversion of a portion of a spectrum obtained by the Voyager infrar spectroscopy experiment. The measured spectrum is denoted by the curve with dots. The solid curve is a spectrum calculated using the vertical distribution of ammonia shown in Fig. 8.3.3. For comparison, a spectrum calculated assuming a saturated ammonia distribution is indicated by the broken curve. Sample error bars are shown below the curves (Kunde et al., 1982).

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