Doppler broadening

About: Doppler broadening is a research topic. Over the lifetime, 5509 publications have been published within this topic receiving 92552 citations.

Spectral broadening and pulse duration reduction during cross-polarized wave generation: influence of the quadratic spectral phase

Abstract: Cross-polarized wave (XPW) generation is used for the contrast improvement of ultra-intense femtosecond laser pulses in a double CPA configuration. We present theoretical and experimental evidence that the XPW output spectrum depends in a predictable way on the input chirp. Therefore, a chirp controlled pulse can experience a pulse duration shortening up to a factor of \(\sqrt{3}\), and an initial amount of chirp that leads to the exact preservation of the spectral width of a given pulse can be predicted.

Collision Broadening of Rotational Absorption Lines. IV. Pressure Broadening of the Ammonia Inversion Spectrum

Abstract: The collision broadening of the NH3 inversion spectrum was investigated within the framework of an earlier proposed theory of pressure broadening. The original treatment must be modified before application to NH3 to allow for the fact that NH3 has two closely spaced energy levels, the inversion doublet, with all other levels very widely spaced. This situation results in a “two‐level resonance” system which greatly affects the linewidth. In general, the agreement between the calculated and experimental values is very good although the calculated values tend to be slightly smaller. Molecular quadrupole moments for N2 and H2 are determined from linewidth data for broadening of NH3 inversion lines and are in excellent agreement with values determined by other methods.

Photoionization of hydrogen in atmospheres of magnetic neutron stars

Abstract: The strong magnetic fields (B ~ 1012-1013 G) characteristic of neutron stars make all the properties of an atom strongly dependent on the transverse component K⊥ of its generalized momentum. In particular, the photoionization process is modified substantially: (1) threshold energies are decreased as compared with those for an atom at rest, (2) cross section values are changed significantly, and (3) selection rules valid for atoms at rest are violated by the motion so that new photoionization channels become allowed. To calculate the photoionization cross sections, we employ, for the first time, exact numerical treatment of both initial and final atomic states. This enables us to take into account the quasi-bound (autoionizing) atomic states as well as coupling of different ionization channels. We extend the previous consideration, restricted to the so-called centered states corresponding to relatively small values of K⊥, to arbitrary states of atomic motion. We fold the cross sections with the thermal distribution of atoms over K. For typical temperatures of neutron star atmospheres, the averaged cross sections differ substantially from those of atoms at rest. In particular, the photoionization edges are strongly broadened by the thermal motion of atoms; this "magnetic broadening" exceeds the usual Doppler broadening by orders of magnitude. The decentered states of the atoms give rise to the low-energy component of the photoionization cross section. This new component grows significantly with increasing temperature above 105.5 K and decreasing density below 1 g cm-3, i.e., for the conditions expected in atmospheres of middle-aged neutron stars.