Influence of asymmetry and nodal planes on high-harmonic generation in heteronuclear molecules

The relation between high-harmonic spectra and the geometry of the molecular orbitals in position and momentum space is investigated. In particular we choose two isoelectronic pairs of homonuclear and heteronuclear molecules, such that the highest occupied molecular orbital of the former exhibit at least one nodal plane. The imprint of such planes is a strong suppression in the harmonic spectra, for particular alignment angles. We are able to identify two distinct types of nodal planes. If the nodal planes are determined by the atomic wavefunctions only, the angle for which the yield is suppressed will remain the same for both types of molecules. In contrast, if they are determined by the linear combination of atomic orbitals at different centers in the molecule, there will be a shift in the angle at which the suppression occurs for the heteronuclear molecules, with regard to their homonuclear counterpart. This shows that, in principle, molecular imaging, which uses the homonuclear molecule as a reference and enables one to observe the wavefunction distortions in its heteronuclear counterpart, is possible.Comment: 14 pages, 7 figures. Figs. 3, 5 and 6 have been simplified in order to comply with the arXiv size requirement

Existence criteria for stabilization from the scaling behaviour of ionization probabilities

We provide a systematic derivation of the scaling behaviour of various quantities and establish in particular the scale invariance of the ionization probability. We discuss the gauge invariance of the scaling properties and the manner in which they can be exploited as consistency check in explicit analytical expressions, in perturbation theory, in the Kramers-Henneberger and Floquet approximation, in upper and lower bound estimates and fully numerical solutions of the time dependent Schroedinger equation. The scaling invariance leads to a differential equation which has to be satisfied by the ionization probability and which yields an alternative criterium for the existence of atomic bound state stabilization.Comment: 12 pages of Latex, one figur

Coulomb-corrected quantum interference in above-threshold ionization: Working towards multi-trajectory electron holography

Using the recently developed Coulomb Quantum Orbit Strong-Field Approximation (CQSFA), we perform a systematic analysis of several features encountered in above-threshold ionization (ATI) photoelectron angle-resolved distributions (PADs), such as side lobes, and intra- and intercycle interference patterns. The latter include not only the well-known intra-cycle rings and the near-threshold fan-shaped structure, but also previously overlooked patterns. We provide a direct account of how the Coulomb potential distorts different types of interfering trajectories and changes the corresponding phase differences, and show that these patterns may be viewed as generalized holographic structures formed by up to three types of trajectories. We also derive analytical interference conditions and estimates valid in the presence or absence of the residual potential, and assess the range of validity of Coulomb-corrected interference conditions provided in the literature.Comment: 17 pages, 11 figures. Some figures have been compressed in order to comply with the arXiv requirement

Fosfato parcialmente solubilizado em pastagem de capim-bufel no submedio Sao Francisco.

Em um podzolico plintico A fraco, com pH 6,2 e P 2,3 ppm, em Petrolina (PE), no periodo de 1982-86, estudou-se a influencia do fosfato Arafertil parcialmente solubilizado (FAPS), comparado com o superfosfato simples (SS) no rendimento do capim-buffel (Cenchrus ciliaris). Usou-se uma testemunha (sem adicao de fosforo) e aplicaram-se no primeiro ano os niveis de 100 e 200 kg/ha de P2O5 para ambas as fontes de P, com base no P soluvel em acido citrico do FAPS. Avaliou-se o P no solo, a produtividade de materia seca (MS) da forrageira e o equivalente a superfosfato simples (EqSS). Os teores de fosforo no solo extraidos pelos metodos Mehlich e Bray 1 nos tratamentos com SS e por Bray 1 nos tratamentos com FAPS, diminuiram, ao longo dos anos, e por Mehlich, nos tratamentos com FAPS, variaram irregularmente. Pelo Mehlich, a extracao de P foi maior nos tratamentos co FAPS do que com SS, e por Bray 1, isso nao se verificou. Nas parcelas com FAPA, a extracao de P foi maior pelo metodo Mehlich do que pelo Bray 1, enquando nas parcelas com SS nao ocorreram diferencas significativas. A analise de variancia dos dados de MS indicou uma resposta positiva da planta a aplicacao de fosforo ao solo, mas nao diferencas significativas entre as fontes de P. O EqSS do FAPS foi de 38,5%. Se o preco do FAPS, com base no fosforo soluvel em acido citrico, for igual ou inferior ao do SS, sera viavel seu uso na adubacao da pastagem de capim-buffel

Disponibilidade e correcao do nivel de fosforo em solo do Submedio Sao Francisco em relacao ao rendimento do capim-bufel.

Estudou-se em um Podzolico Plintico do submedio Sao Francisco, relacao entre os teores de fosforo no solo e o rendimento do capim-bufel (Cenchrus ciliaris). Os diferentes teores foram criados por meio de adicao previa de quantidades crescentes de fosfato ao solo. De acordo com o rendimento relativo do capim, os teores de fosforo no solo foram classificados como: muito baixo, P ate 3,5 ppm; baixo, P de 3,6 ppm a 6,5 ppm e 3,6 ppm a 6,8 ppm; medio, P de 6,6 ppm a 10,5 ppm e 6,9 ppm a 10,0 ppm; alto, P de 10,6 ppm a 20 ppm e 10,1 ppm a 17,7 ppm; e muito alto, P superior a 20 ppm e 17,7 ppm pelos metodos de Mehlich e Bray 1, respectivamente. As doses de fosforo necessarias para corrigir o solo em cada um desses niveis, nessa mesma sequencia, seriam: 200, 150, 120, 50 e 0 kg/ha de P2O5. A exportacao de fosforo pela planta correspondeu a 24,9 kg/ha/ano de P2O5, na condicao de producao maxima de materia seca (8.700 kg/ha)