The B2Π−^2\Pi-X2Π^2\Pi electronic origin band of 13^{13}C6_6H

The rotationally resolved spectrum of the B$^2\Pi-$X$^2\Pi$ electronic origin band transition of $^{13}$C$_6$H is presented. The spectrum is recorded using cavity ring-down spectroscopy in combination with supersonic plasma jets by discharging a $^{13}$C$_2$H$_2$/He/Ar gas mixture. A detailed analysis of more than a hundred fully-resolved transitions allows for an accurate determination of the spectroscopic parameters for both the ground and electronically excited state of $^{13}$C$_6$H.Comment: 4 pages, 1 figure, 2 table

UV frequency metrology on CO (a3Pi); isotope effects and sensitivity to a variation of the proton-to-electron mass ratio

UV frequency metrology has been performed on the a3Pi - X1Sigma+ (0,0) band of various isotopologues of CO using a frequency-quadrupled injection-seeded narrow-band pulsed Titanium:Sapphire laser referenced to a frequency comb laser. The band origin is determined with an accuracy of 5 MHz (delta \nu / \nu = 3 * 10^-9), while the energy differences between rotational levels in the a3Pi state are determined with an accuracy of 500 kHz. From these measurements, in combination with previously published radiofrequency and microwave data, a new set of molecular constants is obtained that describes the level structure of the a3Pi state of 12C16O and 13C16O with improved accuracy. Transitions in the different isotopologues are well reproduced by scaling the molecular constants of 12C16O via the common mass-scaling rules. Only the value of the band origin could not be scaled, indicative of a breakdown of the Born-Oppenheimer approximation. Our analysis confirms the extreme sensitivity of two-photon microwave transitions between nearly-degenerate rotational levels of different Omega-manifolds for probing a possible variation of the proton-to-electron mass ratio, \mu=m_p/m_e, on a laboratory time scale

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

An extensive survey of the D2 absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer of the DESIRS beamline at the SOLEIL synchrotron. The frequency range of 90 000-119 000 cm-1 covers the full depth of the potential wells of the B 1{\Sigma}+u, B' 1{\Sigma}+u, and C 1{\Pi}u electronic states up to the D(1s) + D(2\ell) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ~0.35 cm-1. Extended calibration methods are employed to extract line positions of D2 lines at absolute accuracies of 0.03 cm-1. The D1{\Pi}u and B" 1{\Sigma}+u electronic states correlate with the D(1s) + D(3\ell) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D2. The observations are compared with previous studies, both experimental and theoretical.Comment: 13 pages, 6 figures. The second set of Tables (Tables I-IV after the references), is auxiliary materia

A Spectroscopic Survey of Electronic Transitions of C6_6H, 13^{13}C6_6H, and C6_6D

Electronic spectra of C$_6$H are measured in the $18\,950-21\,100$ cm$^{-1}$ domain using cavity ring-down spectroscopy of a supersonically expanding hydrocarbon plasma. In total, 19 (sub)bands of C$_6$H are presented, all probing the vibrational manifold of the B$^2\Pi$ electronically excited state. The assignments are guided by electronic spectra available from matrix isolation work, isotopic substitution experiments (yielding also spectra for $^{13}$C$_6$H and C$_6$D), predictions from ab initio calculations as well as rotational fitting and vibrational contour simulations using the available ground state parameters as obtained from microwave experiments. Besides the $0_0^0$ origin band, three non-degenerate stretching vibrations along the linear backbone of the C$_6$H molecule are assigned: the $\nu_6$ mode associated with the C-C bond vibration and the $\nu_4$ and $\nu_3$ modes associated with C$\equiv$C triple bonds. For the two lowest $\nu_{11}$ and $\nu_{10}$ bending modes, a Renner-Teller analysis is performed identifying the $\mu^2\Sigma$($\nu_{11}$) and both $\mu^2\Sigma$($\nu_{10}$) and $\kappa^2\Sigma$($\nu_{10}$) components. In addition, two higher lying bending modes are observed, which are tentatively assigned as $\mu^2\Sigma$($\nu_9$) and $\mu^2\Sigma$($\nu_8$) levels. In the excitation region below the first non-degenerate vibration ($\nu_6$), some $^2\Pi-^{2}\Pi$ transitions are observed that are assigned as even combination modes of low-lying bending vibrations. The same holds for a $^2\Pi-^{2}\Pi$ transition found above the $\nu_6$ level. From these spectroscopic data and the vibronic analysis a comprehensive energy level diagram for the B$^2\Pi$ state of C$_6$H is derived and presented.Comment: Accepted for publication in The Journal of Physical Chemistry A (26 July 2016

Benchmarking theory with an improved measurement of the ionization and dissociation energies of H2_2

The dissociation energy of H$_2$ represents a benchmark quantity to test the accuracy of first-principles calculations. We present a new measurement of the energy interval between the EF $^1\Sigma_g^+(v=0,N=1)$ state and the 54p1$_1$ Rydberg state of H$_2$. When combined with previously determined intervals, this new measurement leads to an improved value of the dissociation energy $D_0^{N=1}$ of ortho-H$_2$ that has, for the first time, reached a level of uncertainty that is three times smaller than the contribution of about 1 MHz resulting from the finite size of the proton. The new result of 35999.582834(11) cm$^{-1}$ is in remarkable agreement with the theoretical result of 35999.582820(26) cm$^{-1}$ obtained in calculations including high-order relativistic and quantum electrodynamics corrections, as reported in the companion article (M. Puchalski, J. Komasa, P. Czachorowski and K. Pachucki, submitted). This agreement resolves a recent discrepancy between experiment and theory that had hindered a possible use of the dissociation energy of H$_2$ in the context of the current controversy on the charge radius of the proton

Analysis of hybrid mode-locking of two-section quantum dot lasers operating at 1.5 micron

For the first time a detailed study of hybrid mode-locking in two- section InAs/InP quantum dot Fabry-Pérot-type lasers is presented. The output pulses have a typical upchirp of approximately 8 ps/nm, leading to very elongated pulses. The mechanism leading to this typical pulse shape and the phase noise is investigated by detailed radio-frequency and optical spectral studies as well as time-domain studies. The pulse shaping mechanism in these lasers is found to be fundamentally different than the mechanism observed in conventional mode-locked laser diodes, based on quantum well gain or bulk material. ©2009 Optical Society of America