J. Robert Huber

Bio: J. Robert Huber is an academic researcher from University of Zurich. The author has contributed to research in topics: Photodissociation & Excited state. The author has an hindex of 36, co-authored 151 publications receiving 4143 citations. Previous affiliations of J. Robert Huber include University of Konstanz.

Sub‐Doppler laser‐induced fluorescence measurements of the velocity distribution and rotational alignment of NO photofragments

Abstract: The photodissociation of dimethylnitrosamine, (CH3)2N–NO, at 363.5 nm produces ro‐vibrationally excited NO fragments. With two‐photon laser‐induced fluorescence the Doppler profiles of single rotational transitions were probed, using various polarization schemes for dissociation and probe lasers. These measurements provided a detailed product state distribution, the three‐dimensional recoil velocity distribution of specific fragment states, and the alignment of their angular momentum. We present evidence of the presence of correlations between fragment recoil direction and alignment of fragment angular momentum.

Photodissociation of methylnitrite: State distributions, recoil velocity distribution, and alignment effects of the NO(X 2Π) photofragment

Abstract: The photodissociation of CH3ONO→CH3O+NO at 363.9 nm generates vibrationally, rotationally, and translationally excited fragments (fNOvib =3%, fNOrot =15%, fNOtrans =33%). By means of two‐photon LIF and sub‐Doppler spectroscopy in combination with various polarization schemes of dissociation and probe lasers, the nascent NO(X 2Π) photofragment was characterized with respect to state distributions and three‐dimensional recoil velocity distribution. Furthermore, the rotational alignment and the Λ‐state populations were determined. Through the rotational alignment dependence of Doppler profiles probed by differently polarized transitions (R and S), the J–v vector correlation was assessed. Based on these results, stereochemical and dynamical information about the dissociation was obtained which shows that the fragmentation process is planar and takes place within 210 fs.

The photoreaction N2O→O(1D)+N2(1Σ) at 193 nm studied by photofragment translational spectroscopy

Abstract: Polarized laser photodissociation of N 2 O at 193 nm, investigated by the time-of-light, crossed laser-molecular-beam method, generates the fragments N 2 ( 1 Σ + g ) and O( 1 D 2 ) with an average translational energy of 26.8 kcal/mol (42% E avl ), corresponding to an average internal energy of N 2 of 37.6 kcal/mol (58% E avl ), where E avl is the available energy. A substantial part of the latter consists of rotational energy, most likely due to the bent excited electronic state of N 2 O. The recoil anisotropy parameter was measured to be β=0.48±0.2.

The vibrational predissociation of cis‐methyl nitrite in the S1 state: A comparison of exact quantum mechanical wave packet calculations with classical trajectory calculations and detailed experimental results

Abstract: We present quantum mechanical wave packet calculations for the vibrational predissociation of cis‐CH3ONO in the S1 state including three degrees of freedom—the CH3O–NO dissociation bond, the N=O stretching coordinate, and the CH3O–N–O bending angle. We calculate the autocorrelation function, the absorption spectrum, the lifetimes of the excited complex as a function of the internal excitation, and the final vibrational‐rotational state distributions of the NO fragment. The lifetimes and the product state distributions are compared with experimental data as well as with previous results obtained from classical trajectory calculations. The calculated vibrational state distributions of the NO product satisfactorily reproduce the systematic variation with the initially prepared quasibound state of the CH3ONO(S1) complex found experimentally; however, they are considerably narrower than the experimental distributions. The theoretical rotational state distributions of NO, all being highly inverted and having th...

Fano resonances in nanoscale structures

Abstract: Modern nanotechnology allows one to scale down various important devices (sensors, chips, fibers, etc.) and thus opens up new horizons for their applications. The efficiency of most of them is based on fundamental physical phenomena, such as transport of wave excitations and resonances. Short propagation distances make phase-coherent processes of waves important. Often the scattering of waves involves propagation along different paths and, as a consequence, results in interference phenomena, where constructive interference corresponds to resonant enhancement and destructive interference to resonant suppression of the transmission. Recently, a variety of experimental and theoretical work has revealed such patterns in different physical settings. The purpose of this review is to relate resonant scattering to Fano resonances, known from atomic physics. One of the main features of the Fano resonance is its asymmetric line profile. The asymmetry originates from a close coexistence of resonant transmission and resonant reflection and can be reduced to the interaction of a discrete (localized) state with a continuum of propagation modes. The basic concepts of Fano resonances are introduced, their geometrical and/or dynamical origin are explained, and theoretical and experimental studies of light propagation in photonic devices, charge transport through quantum dots, plasmon scattering in Josephson-junction networks, and matter-wave scattering in ultracold atom systems, among others are reviewed.

The multiconfiguration time-dependent Hartree (MCTDH) method: a highly efficient algorithm for propagating wavepackets

Abstract: A review is given on the multiconfiguration time-dependent Hartree (MCTDH) method, which is an algorithm for propagating wavepackets. The formal derivation, numerical implementation, and performance of the method are detailed. As demonstrated by example applications, MCTDH may perform very efficiently, especially when there are many (typically four to twelve, say) degrees of freedom. The largest system treated with MCTDH to date is the pyrazine molecule, where all 24 (!) vibrational modes were accounted for. The particular representation of the MCTDH wavefunction requires special techniques for generating an initial wavepacket and for analysing the propagated wavefunction. These techniques are discussed. The full efficiency of the MCTDH method is only realised if the Hamiltonian can be written as a sum of products of one-dimensional operators. The kinetic energy operator and many model potential functions already have this required structure. For other potential functions, we describe an efficient algorithm for determining optimal fits of product form. An alternative to the product representation, the correlation discrete variable representation (CDVR) method, is also briefly discussed.

The Quantum Theory of Light

Abstract: (b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>