We discuss a treacherous point in light-front dynamics (LFD) which should be taken into account to restore complete equivalence with the manifestly covariant formalism. We present examples that require an inclusion of the arc contribution in the light-front energy contour integration in order to achieve the equivalence between the LFD result and the manifestly covariant result.
The effect of vibrational pre-excitation of anions on their photoelectron spectra is explored, combining slow photoelectron velocitymap imaging of cryogenically cooled anions (cryo-SEVI) with tunable IR radiation to pre-excite the anions. This new IR cryo-SEVI method is applied to OH − as a test system, where the R(0) transition of the hydroxyl anion (3591.53 cm −1 ) is pumped. Vibrational excitation induces a 30% depletion in photodetachment signal from the v = 0, J = 0 ground state of the anion and the appearance of all five allowed, rotationally resolved photodetachment transitions from the OH − (v = 1, J = 1) level, each with peak widths between 1 and 2 cm −1 . By scanning the IR laser, IR cryo-SEVI can also serve as a novel action technique to obtain the vibrational spectrum of OH − , giving an experimental value for the R(0) transition of 3591(1.2) cm −1 .
High-resolution anion photoelectron spectra of cryogenically cooled NO 3ˉ anions obtained using slow photoelectron velocity-map imaging are presented and provide new insight into the vibronic structure of the corresponding neutral radical. A combination of improved spectral resolution, measurement of energy-dependent intensity effects, temperature control, and comparison to theory allows for full assignment of the vibronic features observed in this spectrum. We obtain a refined electron affinity of 3.9289( 14) eV for NO 3 . Further, the appearance of Franck-Condon forbidden transitions from vibrationally cold anions to neutral states with excitation along the NO 3 v 4 mode confirms that these features arise from vibronic coupling with the excited state of NO 3 and are not hot bands as has been suggested. Together, the suite of experimental and simulated results provides clear evidence that the v 3 fundamental of NO 3 resides near 1050 cm −1 , addressing a long-standing controversy surrounding this vibrational assignment. File list (2) download file view on ChemRxiv NO3_SI.pdf (208.75 KiB) download file view on ChemRxiv NO3_FINAL.pdf (722.77 KiB)
We construct a relativistic 3 P 0 wave function for scalar mesons within the framework of the light-front quark model ͑LFQM͒. This scalar wave function is used to perform relativistic calculations of absolute widths for the radiative decay processes (0 ϩϩ )→␥␥, (0 ϩϩ )→␥, and (0 ϩϩ )→␥ which incorporate the effects of glueball-qq mixing. The mixed physical states are assumed to be f 0 (1370), f 0 (1500), and f 0 (1710) for which the flavor-glue content is taken from the mixing calculations of other works. Since experimental data for these processes are poor, our results are compared with those of a recent non-relativistic model calculation. We find that while the relativistic corrections introduced by the LFQM reduce the magnitudes of the decay widths by 50-70 %, the relative strengths between different decay processes are fairly well preserved. We also calculate decay widths for the processes →(0 ϩϩ )␥ and (0 ϩϩ )→␥␥ involving the light scalars f 0 (980) and a 0 (980) to test the simple qq model of these mesons. Our results of the qq model for these processes are not consistent with well-established data, further supporting the idea that f 0 (980) and a 0 (980) are not conventional qq states.
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