26 research outputs found
Cavity-assisted manipulation of freely rotating silicon nanorods in high vacuum
Optical control of nanoscale objects has recently developed into a thriving
field of research with far-reaching promises for precision measurements,
fundamental quantum physics and studies on single-particle thermodynamics.
Here, we demonstrate the optical manipulation of silicon nanorods in high
vacuum. Initially, we sculpture these particles into a silicon substrate with a
tailored geometry to facilitate their launch into high vacuum by laser-induced
mechanical cleavage. We manipulate and trace their center-of-mass and
rotational motion through the interaction with an intense intra-cavity field.
Our experiments show optical forces on nanorotors three times stronger than on
silicon nanospheres of the same mass. The optical torque experienced by the
spinning rods will enable cooling of the rotational motion and torsional
opto-mechanics in a dissipation-free environment.Comment: 8 page
Strong-field physics with mid-IR fields
Strong-field physics is currently experiencing a shift towards the use of
mid-IR driving wavelengths. This is because they permit conducting experiments
unambiguously in the quasi-static regime and enable exploiting the effects
related to ponderomotive scaling of electron recollisions. Initial measurements
taken in the mid-IR immediately led to a deeper understanding of
photo-ionization and allowed a discrimination amongst different theoretical
models. Ponderomotive scaling of rescattering has enabled new avenues towards
time resolved probing of molecular structure. Essential for this paradigm shift
was the convergence of two experimental tools: 1) intense mid-IR sources that
can create high energy photons and electrons while operating within the
quasi-static regime, and 2) detection systems that can detect the generated
high energy particles and image the entire momentum space of the interaction in
full coincidence. Here we present a unique combination of these two essential
ingredients, namely a 160\~kHz mid-IR source and a reaction microscope
detection system, to present an experimental methodology that provides an
unprecedented three-dimensional view of strong-field interactions. The system
is capable of generating and detecting electron energies that span a six order
of magnitude dynamic range. We demonstrate the versatility of the system by
investigating electron recollisions, the core process that drives strong-field
phenomena, at both low (meV) and high (hundreds of eV) energies. The low energy
region is used to investigate recently discovered low-energy structures, while
the high energy electrons are used to probe atomic structure via laser-induced
electron diffraction. Moreover we present, for the first time, the correlated
momentum distribution of electrons from non-sequential double-ionization driven
by mid-IR pulses.Comment: 17 pages, 11 figure
Imaging the Renner-Teller effect using laser-induced electron diffraction
Structural information on electronically excited neutral molecules can be
indirectly retrieved, largely through pump-probe and rotational spectroscopy
measurements with the aid of calculations. Here, we demonstrate the direct
structural retrieval of neutral carbonyl disulfide (CS) in the BB
excited electronic state using laser-induced electron diffraction (LIED). We
unambiguously identify the ultrafast symmetric stretching and bending of the
field-dressed neutral CS molecule with combined picometer and attosecond
resolution using intrapulse pump-probe excitation and measurement. We invoke
the Renner-Teller effect to populate the BB excited state in neutral
CS, leading to bending and stretching of the molecule. Our results
demonstrate the sensitivity of LIED in retrieving the geometric structure of
CS, which is known to appear as a two-center scatterer
Prospezioni sismiche, geoelettriche ed elettromagnetiche ad alta risoluzione in prossimità della foce del Fiume Volturno
Nell’ambito dell’Obiettivo Realizzativo 2.3 “Sviluppo e allestimento di sensoristica e sistemi innovativi per osservazioni dell’iterazione terra-aria per la qualità dell’aria e degli ecosistemi agro-forestali” del progetto PON I-AMICA (Infrastruttura di Alta tecnologia per il Monitoraggio Integrato Climatico-Ambientale), l’Istituto per l’Ambiente Marino Costiero del Consiglio Nazionale delle Ricerche (CNR-I.A.M.C.) di Napoli, coordinato dal dott. Vincenzo Di Fiore, ha eseguito delle prospezioni sismiche, geoelettriche ed elettromagnetiche in un’area prospiciente la foce del Fiume Volturno.
Tali indagini hanno avuto come obiettivo:
La valutazione dell’intrusione nelle falde acquifere di componenti idrosaline provenienti dalla vicina area costiera;
Lo studio, con risoluzione metrica, della porzione superficiale (0 - 80 metri di profondità) del sottosuolo al fine di caratterizzare, in termini di spessori e di velocità di propagazione, le serie riflettive che caratterizzano l’area in esame
Ultrafast imaging of the Renner-Teller effect in a field-dressed molecule
We present experimental results of linear-to-bent transition of field-dressed molecules, mediated by Renner-Teller effect. Using the state-of-the-art laser-induced electron diffraction (LIED) technique, we image a bent and symmetrically stretched carbon disulfide (CS2) molecule populating an excited electronic state under the influence of strong laser field. Our findings are well-supported by ab initio quantum mechanical calculations.Peer ReviewedPostprint (published version
Sequence variation in mature microRNA-608 and benefit from neo-adjuvant treatment in locally advanced rectal cancer patients
Single nucleotide polymorphisms (SNPs) in microRNA genes have been associated with colorectal cancer (CRC) risk, survival and response to treatment. Conflicting results are available on the association between rs4919510, a SNP in mature miR-608 and clinical outcome in CRC. Here, we analyzed the association between rs4919510 and benefit from perioperative treatment in a randomised phase II trial of neoadjuvant Capecitabine and Oxaliplatin (CAPOX) followed by chemo-radiotherapy, surgery and adjuvant CAPOX ± Cetuximab in high-risk locally advanced rectal cancer (LARC). A total of 155/164 (94.5%) patients were assessable. 95 (61.3%) were homozygous for CC, 55 (35.5%) heterozygous (CG) and 5 (3.2%) homozygous for GG. Median follow-up was 64.9 months. In the CAPOX arm the 5-year progression-free survival (PFS) and overall survival (OS) rates were 54.6% and 60.7% for CC and 82.0% and 82.1% for CG/GG, respectively (HR PFS 0.13, 95% CI: 0.12-0.83, P = 0.02; HR OS 0.38, 95% CI: 0.14-1.01, P = 0.05). In the CAPOX-C arm PFS and OS were 73.2 and 82.2%, respectively for CC carriers and 64.6 and 73.1% for CG/GG carriers (HR PFS 1.38, 95% CI: 0.61-3.13, P = 0.44; HR OS 1.34, 95% CI: 0.52-3.48, P = 0.55). An interaction was found between study treatment and rs4919510 genotype for both PFS (P = 0.02) and OS (P = 0.07). This is the first study investigating rs4919510 in LARC. The CC genotype appeared to be associated with worse prognosis compared to the CG/GG genotype in patients treated with chemotherapy and chemo-radiotherapy alone. Addition of Cetuximab to chemotherapy and chemo-radiotherapy in CC carriers appeared to improve clinical outcome
Molecular beam methods for quantum optics experiments
Die Molekülinterferometrie ist inzwischen ein weites Forschungsfeld. Sie bietet einerseits die Möglichkeit, an grundlegende Fragen der Quantenmechanik zu forschen und andererseits die Option molekulare Eigenschaften zu bestimmen. Für die Realisierung des Welle-Teilchen Dualismus mit sehr massiven Teilchen müssen neuartige Methoden entwickelt werden um neutrale, langsame Moleküle in einen Strahl zu bringen. Darüber hinaus benötigt man neue Detektionsmechanismen, um einzelne Moleküle nachweisen zu können.
Der erste Teil meiner Dissertation beinhaltet die Charakterisierung eines neuartigen supraleitenden Nanodrahtdetektors. Dieser wurde ursprünglich zum Nachweis von einzelnen Photonen entworfen und wird daher häufig auch als supraleitender Einzelphotondetektor bezeichnet. Ich konnte mit diesem Detektor neutrale, massive Teilchen grundsätzlich detektieren und die Detektionsempfindlichkeit für Ionen im Detail charakterisieren. Dazu wird in ein niederenergetischer He+-Strahl (0.2-1keV) verwendet. Abschließend diskutiere ich potentielle Anwendungen dieses neuartigen Detektors für die Massenspektroskopie.
Im zweiten Teil meiner Arbeit widme ich mich der Untersuchung der Rolle von van der Waals Potentialen bei der Beugung von Molekülen am einzelnen Gitter. Um die Wechselwirkung zwischen polarisierbaren Molekülen (PcH2 – 514u) und SiN Oberflächen zu untersuchen, werden Interferogramme hinter verschiedenen Beugungsgittern (100 nm Periodizität und Dicken zwischen 10 – 90 nm) gemessen und ausgewertet. Die Vorhersagen theoretischer Modelle werden dabei getestet und die Ergebnisse diskutiert.
Abschließend untersuche ich die Beugung von Phthaloncynaninen (PcH2) an einer biologisch gewachsenen Nanostruktur, nämlich dem aus SiO2 bestehenden Skelett der Alge Amphipleura pellucida. Die Ergebnisse untermauern die Rolle der van der Waals Wechselwirkungen in der Materiewellenbeugung an einzelnen Gittern. Sie zeigen, dass Experimente zur kohärenten Kontrolle von Molekülstrahlen, z.B. bei der Holographie mit komplexen Molekülen, in naher Zukunft durchgeführt werden können.Molecular matter-wave interferometry has become a broad research field, spanning experiments from the foundations of quantum mechanics to advanced quantum-assisted metrology. The experimental demonstration of the particle-wave dualism with particles with increasing mass and complexity requires the exploration of novel beam methods for the production of neutral slow molecules as well as the investigation of new detection schemes with single particle sensitivity.
The first part of my PhD focused on the characterization of a novel superconducting nano-wire detector which was originally developed for the detection of single photons and therefore often referred to as a Superconducting Single Photon Detector (SSPD). I provide a proof-of-principle for the detection of neutral massive particles together with a comprehensive
characterization of the SSPD sensitivity for ions. The detection efficiency of SSPDs is studied with a beam of low energetic He+ (0.2-1 keV) and their potential applications to mass spectroscopy are discussed.
The second part of my thesis is dedicated to the investigation of the role of van derWaals potentials in single-grating diffraction in the far-field with molecular matter-waves. The interaction between polarizable molecules (PcH2 - 514 u) and SiN surfaces is explored by evaluating the interference patterns collected behind different diffraction gratings (100 nm periodicity, thickness 10 - 90 nm). The validity of the existing theoretical models is discussed. Finally, I illustrate the coherent propagation of PcH2 through a biologically grown nano-structure, namely the SiO2 frustule of the alga
Amphipleura pellucida. The results corroborate the role of van der Waals interaction in matter-wave single-grating diffraction and demonstrate the feasibility of the realization in the near future of coherent control schemes, e.g. holography, with complex molecules