Narrow-band tunable extreme-ultraviolet laser source for lifetime measurements and precision spectroscopy

Abstract

A narrow-band, extreme-ultraviolet laser source is developed that has continuous tunability in the range 96-97.5 nm and a bandwidth below 250 MHz. The versatility of the radiation source is demonstrated in two applications. Accurate values for lifetimes of highly excited molecular quantum states are determined from line-broadening measurements in three electronic states of CO:The application of the source in metrology in the extreme-ultraviolet domain is demonstrated by the highly accurate, absolute calibration of narrow resonances in CO. These molecular lines can be used for future reference standards at these short wavelengths. From accurately determined minute frequency shifts near the accidentally predissociated J f ϭ 7 level of the L 1 ⌸, v ϭ 0 state the perturber state is characterized as a yet unidentified Rydberg state with an origin at 103 266.92 cm Ϫ1 . It is demonstrated that molecular spectroscopy in the extreme-ultraviolet domain at megahertz precision is possible.

Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: Wavelength, pressure, and temperature dependency

“…Rotational and parity (e/f) resolved lifetimes of L 1 Π, W 1 Π and K 1 Σ + excited states have been experimentally determined using a narrow band extreme-UV laser source 46 . For the W 1 Π state, a radiative lifetime of 4 nanosecond was derived 47 through ab initio calculations.…”

“…For the W 1 Π state, a radiative lifetime of 4 nanosecond was derived 47 through ab initio calculations. Convoluting the experimentally determined natural lifetime of 130 ps with the radiative lifetime, Ubachs et al 46 concluded that the Π f (f-parity) component of W 1 Π (v=0) state is predissociated by 96.6 % and the 3.3% radiative decay will populate the vibrationally excited states of the electronic ground state. The experimentally determined 1.0 nanosecond lifetime of (4pπ)L 1 Π, ν=0 was suggested to be an effect of purely radiative decay 46 .…”

“…Convoluting the experimentally determined natural lifetime of 130 ps with the radiative lifetime, Ubachs et al 46 concluded that the Π f (f-parity) component of W 1 Π (v=0) state is predissociated by 96.6 % and the 3.3% radiative decay will populate the vibrationally excited states of the electronic ground state. The experimentally determined 1.0 nanosecond lifetime of (4pπ)L 1 Π, ν=0 was suggested to be an effect of purely radiative decay 46 . These non-predissociative/ partial-predissociative states may generate an isotope effect upon the end product (e.g., predissociation product (Oatom) by the entire synchrotron band).…”

Observation of molecular hyperfine structure in the extreme ultraviolet: The HF C-X spectrum

“…Relative frequency measurements are performed by comparing the XUV spectrum with the transmission markers of an actively stabilized etalon, for which the visible output of the ring-dye laser at the fundamental wavelength is used. While in absolute measurements the accuracy of the frequency scale is limited by chirp effect in the PDA system, 26 for the present relative measurements, the uncertainty is reduced to a few megahertz as the chirp effect is considered to be equal over the small frequency intervals of the scans. Hence the uncertainty in the derived hyperfine parameters is primarily due to the statistics of the fitting procedures.…”

“…26 In short, the output of a continuous-wave ring-dye laser operating near 570 nm is amplified in a three-stage pulsed-dye amplifier ͑PDA͒, then frequency-doubled in a KDP nonlinear crystal and subsequently frequency tripled in a pulsed jet of xenon gas. Coherent radiation, tunable in the wavelength range near 95 nm is produced in a forwardly directed beam at sub-nanojoule pulse energies and at a bandwidth of 250-350 MHz, depending on specific alignment and conditions.…”