Strong-field approximation for harmonic generation in diatomic molecules

The generation of high-order harmonics in diatomic molecules is investigated within the framework of the strong-field approximation. We show that the conventional saddle-point approximation is not suitable for large internuclear distances. An adapted saddle-point method that takes into account the molecular structure is presented. We analyze the predictions for the harmonic-generation spectra in both the velocity and the length gauge. At large internuclear separations, we compare the resulting cutoffs with the predictions of the simple-man's model. Good agreement is obtained only by using the adapted saddle-point method combined with the velocity gauge.Comment: 24 pages, 7 figure

The effect of dressing on high-order harmonic generation in vibrating H2_2 molecules

We develop the strong-field approximation for high-order harmonic generation in hydrogen molecules, including the vibrational motion and the laser-induced coupling of the lowest two Born-Oppenheimer states in the molecular ion that is created by the initial ionization of the molecule. We show that the field dressing becomes important at long laser wavelengths ($\approx 2 \mu$m), leading to an overall reduction of harmonic generation and modifying the ratio of harmonic signals from different isotopes.Comment: 23 pages, 11 figures, submitted to PR

Control of recollision wave packets for molecular orbital tomography using short laser pulses

The tomographic imaging of arbitrary molecular orbitals via high-order harmonic generation requires that electrons recollide from one direction only. Within a semi-classical model, we show that extremely short phase-stabilized laser pulses offer control over the momentum distribution of the returning electrons. By adjusting the carrier-envelope phase, recollisions can be forced to occur from mainly one side, while retaining a broad energy spectrum. The signatures of the semi-classical distributions are observed in harmonic spectra obtained by numerical solution of the time-dependent Schr\"{o}dinger equation.Comment: 8 pages, 4 figures; v2: Added some extra clarifications; v3: minor grammatical change

Molecular Orbital Tomography using Short Laser Pulses

Recently, a method to image molecular electronic wave functions using high harmonic generation (HHG) was introduced by Itatani \textit{et al.\} [Nature {\textbf{432}}, 876 (2004)]. We show that, while the tomographic reconstruction of general orbitals with arbitrary symmetry cannot be performed with long laser pulses, this becomes possible when extremely short pulses are used. An alternative reconstruction equation based on momentum matrix elements, rather than on dipole matrix elements, is proposed. We present simulations of the procedure for 2D model systems based on numerical solutions of the time-dependent Schr\"{o}dinger equation, and present results from further post-processing of the reconstructed orbitals.Comment: 5 pages, 2 figure

Восстановление стабильности плечевого сустава по модернизированной методике Бристов-Латаржет при привычном вывихе плеча

Modification of Bristow-Latarjet procedure using whole scapular coracoid process on muscle stem placed and fi xed apical at the anterior - inferior edge of the glena, as a continuation of it, allowed in all 26 cases to re-stabilisation of humeral head in joint, without repeated dislocations with functional reabilitation in the most of cases (n=23).Модификация методики Бристов-Латаржет, с использованием всего клювовидного отростка лопатки на мышечной ножке у его верхушке, установленного у передне-нижнего края суставной впадины лопатки и фиксированного 1-2 винтами (иногда дополненные и спицами) обеспечивали во всех 26 случаях восстановление стабильности плечевого сустава и полную функциональную реабилитацию (n = 23)

27-летний опыт проведения эндопротезирования тазобедренного сустава во II-й клинике Клинической Больницы Травматологии и Ортопедии

Our experience of 619 hip arthroplasties (monopolar = 44,4%, bipolar = 25,5%, total = 30,1%) which were performed in femoral neck and trochanteric fractures, and in other orthopedical pathologies of hip joint, also good results in 95% of cases, afford authors to reccomend using this surgical intervention wider.Клинический опыт проведения 619 протезирований тазобедренного сустава (монополярные – 44,4%, биполярные – 25,5% и тотальные – 30,1%), выполненых при переломах шейки бедра, вертельной области при различных ортопедических патологиях тазобедренного сустава, а также достигнутые положительные результаты в 95% случаях позволяют авторам рекомендовать эти хирургические вмешательства к более широкому применению

One and two-center processes in high-order harmonic generation in diatomic molecules: influence of the internuclear separation

We analyze the influence of different recombination scenarios, involving one or two centers, on high-order harmonic generation (HHG) in diatomic molecules, for different values of the internuclear separation. We work within the strong-field approximation, and employ modified saddle-point equations, in which the structure of the molecule is incorporated. We find that the two-center interference patterns, attributed to high-order harmonic emission at spatially separated centers, are formed by the quantum interference of the orbits starting at a center $C_{j}$ and finishing at a different center $C_{\nu }$ in the molecule with those starting and ending at a same center $C_{j}.$ Within our framework, we also show that contributions starting at different centers exhibit different orders of magnitude, due to the influence of additional potential-energy shifts. This holds even for small internuclear distances. Similar results can also be obtained by considering single-atom saddle-point equations and an adequate choice of molecular prefactors.Comment: 8 pages, 5 figure