Manipulation of photon statistics of highly degenerate incoherent radiation

Highly degenerate incoherent radiation has a Gaussian density matrix and a large occupation number of modes f. If it is passed through a weakly transmitting barrier, its counting statistics is close to Poissonian. We show that a second identical barrier, in series with the first, drastically modifies the statistics. The variance of the photocount is increased above the mean by a factor f times a numerical coefficient. The photocount distribution reaches a limiting form with a Gaussian body and highly asymmetric tails. These are general consequences of the combination of weak transmission and multiple scattering.     

1B2u1A1g fluorescence from benzene produced by electron impact (30–1000 eV)

The ¹B_2u → ¹A_1g fluorescence resulting from electron impact (30–1000 eV) on benzene has been studied in the pressure range 10^?4 ?2 × 10^?3 torr. The fluorescence spectrum is compared with the spectrum obtained by other methods. The energy dependence of the absolute emission cross section indicates a small probability for internal conversion from higher singlet states to the ¹B_2u state.     

The rotational excitation and population distribution of OH(A2Σ+) produced by electron impact on water

The rotational excitation and population distributions in OH(A²Σ⁺, υ′ = 0) have been determined by analyzing the OH(A²Σ⁺ → X²Π_i) emission spectrum. The spectrum results from the impact of mon-energetic electrons (0–100 eV) on water vapour. It is shown that these rotational distributions of the OH(A²Σ⁺) state depend on the electron impact energy and have contributions from singlet and triplet states of water. The contribution from each dissociative state of water can be described by a Boltzmann distribution, both in the case of rotational excitation and population.Three distribution parameters (“temperatures”) for rotational excitation are obtained, namely 13800 K and 2900 K for the singlet contributions and 4000 K for the triplet contribution. The corresponding distribution parameters for the rotational population are 30000, 3300, and 4800 K, respectively. The results are discussed in view of recent theoretical calculations on water energy levels.     

Scaling at the chaos threshold for interacting electrons in a quantum Dot

The chaotic mixing by random two-body interactions of many-electron Fock states in a confined geometry is investigated. Two regimes are distinguished in the dependence of the typical number of Fock states that are mixed into an eigenstate on the interaction strength V, the excitation energy varepsilon, and the level spacing Delta. In both regimes the number is large (indicating delocalization in Fock space). However, only the large- V regime is described by the golden rule (indicating chaotic mixing). The crossover region is characterized by a maximum in a scaling function that becomes more pronounced with increasing excitation energy. The scaling parameter that governs the transition is (varepsilonV/Delta(2))ln(Delta/V).     

On the theory of surface diffusion: kinetic versus lattice gas approach

The present paper extends the results of a recent analytic kinetic theory of particle-on-substrate diffusion. The approach treats explicitly the molecule–surface interaction and takes into account inter-molecular interaction within the hard particle approximation. The physics influencing the diffusion pre-exponential factor and mechanisms determining the density dependence of collective diffusivity are discussed. The kinetic results are compared with those of the traditional lattice gas hopping models. Analytical expressions for jump rates in the low density limit are derived, and the density dependence of effective jump rates at finite occupancy is discussed. It is shown how the traditional hopping model oversimplifies the picture of diffusion by neglecting the collision part of the hopping process.