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The photolysis of thin layers of tert- and iso-butyl nitrite, physisorbed on a transparent insulating MgF2 surface, has been investigated. (1+1′)-Resonance-enhanced multiphoton ionization (REMPI) spectroscopy was used to characterize the desorbed NO. For high-J rotational levels, a preference for the Π(A″) Λ-doublet and a small degree of alignment is observed. The axis of alignment is found to be parallel to the plane of polarization of the photolysis laser and perpendicular to the surface normal, indicating a cartwheeling mode of desorption. The photofragment yield (PHOFRY) spectrum of iso-butyl nitrite is also reported.

The 351 nm photolysis of tert- and iso-butyl nitrite adsorbed on MgF 2 held at 75 K has been investigated using resonance-enhanced multi-photon ionisation spectroscopy. Low desorption laser fluences were used to preclude thermal effects. The rotational distribution of desorbed NO( ν ″ = 2) is velocity-dependent, being principally Gaussian at 2000 m s −1 and Boltzmann below 600 m s −1 . The fast molecules suffer no collisions before desorption and their energy distributions are similar to those found in the gas phase. The slower molecules have suffered collisions. At intermediate velocities, the observed distribution is the sum of these two components which populate high and low rotational states respectively.

The dynamics of the photolysis of NO dimers, and subsequent desorption of NO, from a single crystal MgF 2 surface have been investigated using resonance-enhanced multi-photon ionisation spectroscopy. The rotational distribution of NO( ν ″ = 2) is correlated with its velocity. For a velocity of 1500 m s −1 there is a Gaussian distribution of rotational states, peaking at J = 35.5; lower velocities show progressively colder distributions. It is suggested that these changes are due to collisional deactivation of rotation and translation, but not of vibration, of NO( ν , J ) on the surface prior to desorption.

The alkyl nitrites, tert-butyl nitrite and iso-butyl nitrite have been photolysed at 351 nm on a dielectric surface. This involves excitation to the A 1A″ state with two quanta in the localized NO stretching mode of iso-butyl nitrite and three quanta in the case of tert-butyl nitrite. The vibrational, rotational and translational energy distributions of the NO product are compared with the results of previous gas phase work. The vibrational distributions mimic those in the gas phase, but the rotational distributions do not do so.

The authors present a modular approach for the frequency domain analysis of multiphase power systems based on a modified cascading procedure which produces a reduced model for any composite branch comprising a set of cascaded subsystems. The approach is numerically stable and permits changes in the number of phases within each branch. Extended multi-two-port networks which model both passive elements and independent sources are defined and are used to describe both the reduced composite branch models and their constituent subsystems. The modified cascading procedure incorporates existing nodal admittance matrix techniques and determines all voltages and line currents between branch subsystems using the reduced branch models. >

The photolysis of 3-cyclopentenone adsorbed on MgF 2 at 193 nm has been investigated. B state resonance-enhanced multi-photon ionisation spectroscopy was used to probe the vibrational and rotational state of the desorbed CO. The vibrational distribution of the CO is the same as that determined under collision-free conditions in the gas phase. The majority of the desorbed molecules show far lower rotational temperatures and translational energies than are seen in the gas phase, but range up to the high values of 1700 K and 4000 cm −1 for CO( v = 0). These results demonstrate that the rotational mode is neither equilibrated with the surface temperature, nor with a higher temperature caused by local heating.