IRMPD

Figure 4 IRMPD fragmentation spectrum of the species a) SisO20H7" at m/z 550.8 and b) Si2o047Hi22 at m/z 661.7...

BIRD. The first requirement is that since BIRD is a very slow-heating method the observation time has to be long (seconds or minutes). Second, the pressure has to be low (<10-6 torr) so that the risk of dissociation due to collisions with the background gas is negligible. There are close similarities between BIRD and another slow-heating method, IRMPD. 

The activation step can alternatively be performed without gas by means of infrared multiphoton dissociation (IRMPD) or electron capture dissociation (BCD) (Chap. 2.12.2). Both IRMPD and BCD, solely require storage of the ions during their excitation by photons or electrons, respectively. It is one of the most charming properties of FT-ICR-MS/MS that even the accurate mass of the fragment ions can be determined. [216,217]... 

Dunbar, R. C. Moore, D. T. Oomens,/. IR-Spectroscopic Characterization of Acetophenone Complexes with Fe+, Co+, and NT using Free-Electron-Laser IRMPD./. Phys. Chem. A 2006, no, 8316-8326. 

Figure 6. Interferograms before and after normalizing for the variations of C02 laser fluence with functional form similar to that shown in Figure 5. The data shown correspond to emission from vibrationally excited HF, generated from the IRMPD of CH2F2, and are for a delay of 20 jis after photolysis, taken with one laser shot per interferometric mirror position and a Nyquist wavenumber of 7901.4 cm-1.

As an example of the reactions studied using this instrument we consider that between 0(3P) atoms and the CHF (X1 A ) radical [40], Atoms are formed in a microwave discharge of Q2/Ar, and CHF by IRMPD of... 

Figure 8. Three-dimensional representation of the time evolution of the IR chemiluminescence spectra following the IRMPD of CH2F2 in the presence of O atoms. Conditions were 28.5mTorr CH2F2, 12.0mTorr O atoms, 5.09 Torr total pressure, unapodized FWHM resolution of 6.04 cm 1, Nyquist wavenumber 7901.4 cm"1 with the signal obtained for 1 shot per sampling point. The data were digitized at 30 /is resolution, but are shown here with 150/is between spectra and have been corrected for the instrument function. Emission from HF near 4000 cm-1 and CO near 2000 cm-1 is clearly seen. Reproduced with permission from Ref. 40.

Figure 13. Infrared emission following the dissociation of CH2 = CFC1. (a) A spectrum taken at 10/is after 193-nm photolysis of 3-mTorr precursor by the CS method [47], (b) Emission produced following IRMPD of the precursor, in this case at 10 /is delay at a pressure of 40 mTorr using the SS method [108], Emission from HF (v1 — 1-5) is observed, and in both sets of measurements (with lower SNR than shown in the figure), data were taken at a combination of pressure of precursor and delay times such that rotational, as well as vibrational, relaxation was negligible. Figure 13a reproduced with permission from Ref. 47.

Figure 14. Spectra of the products of IRMPD of CH2CFC1 taken under conditions of higher decomposition yield than in Figure 13, brought about by addition of 1.6Torr Ar to 40mTorr of the precursor. At the time of observation, 45

The reaction between ground state oxygen atoms 0(3P) and the monoflu-orocarbene species CHF(X1A ) possesses all three features of the PES discussed above. The reaction proceeds at almost gas-kinetic rate at room temperature [128,129], and the reaction channel (12) to produce CO and HF products in their ground electronic states (in a spin-forbidden process) is one of the most exothermic bimolecular reactions known, and several other product channels, such as reactions (13) and (14) as well as the production of electronically excited states, can occur. Pulsed IR chemiluminescence was observed following IRMPD of 10-40 mTorr of CH2F2 in the presence of O atoms (5-25 mTorr, and measured by titration), and was passed through the SS interferometer and recorded by one of three detectors InSb (1840-... 

Data were summed up to 25 /total pressure 4.5Torr, un-apodized FWHM 9.31 cm-1. Nyquist wavenumber 3950.7 cm-1, 4 shots per point, fluence 82 J cm-2. The positions of the CO v, v—1 band origins are shown together with the detector cut-off point at 1840 cm-1. Reproduced with permission from Ref. 40. 

Figure 19, Emission spectra at 50, 200, and 500 fts following the IRMPD of CF2HC1 (24 mTorr) in the presence of O atoms (11.3 mTorr) and Ar (4.05 Torr), obtained from FTIR emission experiments. Data are unapodized with resolution (FWHM) 3.18cm 1, Nyquist wavenumber 3950cm-1, and were obtained at one C02 laser pulse per sampling point. The P, R envelope of the (0,0,1) - (0,0,0) transition of COz is clearly seen in the 500-/JS data. Reproduced with permission from Ref. 82.

Three methods of NCO formation have been used to study IR emission from reactions (17)—(19), namely IRMPD of C6H5NCO, IRMPD of o-CF3-C6H4-NCO, and reaction (20)... 

Figure 21. Emission in the 1800-2800 cm-1 region following the IRMPD of CH2F2 (25 mTorr) in the presence of NO (lOOmTorr) and Ar (lOTorr). Emission from N20 (001) and C02 (001) are seen at long times following the vibrational cascade of highly excited species their presence at early times [together with CO(v = 1)] was established by cold gas filter experiments. N20 is the dominant emitter, and is believed to originate from the reaction sequence (20), (17).

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