State-resolved molecular beam

More detailed insight into the energy exchange is obtained by the state-resolved molecular beam experiments [37]. As an example for these t) e of experiments. Fig. 3.10a shows TOF distributions from NO molecules in various rotational states (/") coming... 

The time-of-flight spectrum of the H-atom product from the H20 photodissociation at 157 nm was measured using the HRTOF technique described above. The experimental TOF spectrum is then converted into the total product translational distribution of the photodissociation products. Figure 5 shows the total product translational energy spectrum of H20 photodissociation at 157.6 nm in the molecular beam condition (with rotational temperature 10 K or less). Five vibrational features have been observed in each of this spectrum, which can be easily assigned to the vibrationally excited OH (v = 0 to 4) products from the photodissociation of H20 at 157.6 nm. In the experiment under the molecular beam condition, rotational structures with larger N quantum numbers are partially resolved. By integrating the whole area of each vibrational manifold, the OH vibrational state distribution from the H2O sample at 10 K can be obtained. In... 

Undoubtedly, the technique most suited to tackle polyatomic multichannel reactions is the crossed molecular beam (CMB) scattering technique with mass spectrometric detection and time-of-flight (TOF) analysis. This technique, based on universal electron-impact (El) ionization coupled with a quadrupole mass filter for mass selection, has been central in the investigation of the dynamics of bimolecular reactions during the past 35 years.1,9-11 El ionization affords, in principle, a universal detection method for all possible reaction products of even a complex reaction exhibiting multiple reaction pathways. Although the technique is not usually able to provide state-resolved information, especially on a polyatomic... 

Emission spectra of radical cations are obtained by vacuum UV ionization and subsequent laser excitation in noble-gas matrices (see below), or by electron-impact ionization of a beam of neutral parent molecules at energies above the first ionic excited state. After internal conversion to the first excited state, emission may compete more or less successfully with radiationless deactivation. If the experiment is carried out on a supersonic molecular beam one obtains highly resolved emission spectra which, in the case of small molecules, may contain sufficient information to allow a determination of the molecular structure. 

Combining molecular beam techniques with laser state-resolved detection techniques has allowed state-resolved scattering measurements. 

State-resolved inelastic scattering for a wide range of incident conditions ( ), d,) are measured for this system by combining molecular beam techniques with (2 + 1) ion TOF REMPI detection of the scattered molecules [58]. Energy transfer parallel to the surface is measured from the Doppler broadening of the REMPI spectra. Trapping... 

S.D. Chao, S.A. Harich, D.X. Dai, C.C. Wang, X.M. Yang, R.T. Skodje, A fully state and angle resolved study of the H+HD D+H2 reaction Comparison of a molecular beam experiment to ab initio quantum reaction dynamics, J. Chem. Phys. 117 (2002) 8341. 

In the small water clusters with n < 10, the 1Lb state is vertically excited. The absorption spectrum is weakly displaced and the well resolved emission is characterized by the absence of Stokes shift. This behavior has to be compared with that of 1-naphthol in nonprotic solvents with low dielectric constants. In molecular beams, the l-naphthol-(H2O) <10 and -(NH3)B<4 clusters fall into this case. 

Theory quite naturally gives us the initial and final state resolved probabilities, but in experiment this is not always so. The internal state populations in a molecular beam are determined by the temperature of the nozzle used to produce the supersonic expansion. More than one state is present in such a beam. This has been partially overcome in recent years by Raman pumping of the incident molecular beam [66-69]. Laser beams intercept the molecular beam moving a fraction of the molecules into a particular ro-vibrational state (determined by the laser properties). With careful timing of the firing of the probe lasers, it is possible to measure changes in this fraction of molecules and measure some of the final states populated by the scattering process. 

A few studies on the photophysics of rotationally resolved states of formaldehyde have been recently published. A. C. Luntz [J. Chem. Phys., j>9, 3436 (1978)] reported the lifetimes of the K -sublevels of the 4 SVL of I CO in a molecular beam. K. Shibuya and E. K. C. Lee [J. Chem. Phys., 69, 5558 (1978)] reported the fluorescence quantum yields from various rotational levels (J1, K ) of the 41 SVL of H2CO. J. C. Weisshaar and C. 3. Moore [J. Chem. Phys., 7J), 5135 (1979)] reported the collisionless decay rates of single rotational levels of the 4 ... 

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