We have studied multiphoton ionization of Ba 6snl Rydberg states by intense ps pulses and have shown that the duration of the laser pulse compared to the orbit time of the Rydberg electron determines the laser-atom interaction. For high-n states with a long orbit time, the loosely bound Rydberg electron is not affected by the intense laser pulse. Instead the inner electron is ejected by absorption of five photons, leaving the ${\mathrm{Ba}}^{+}$ ion in a Rydberg state. For low-n states the outer electron is ejected and the residual ${\mathrm{Ba}}^{+}$ ion can subsequently be multiphoton ionized to ${\mathrm{Ba}}^{++}$ .We have studied multiphoton ionization of Ba 6snl Rydberg states by intense ps pulses and have shown that the duration of the laser pulse compared to the orbit time of the Rydberg electron determines the laser-atom interaction. For high-n states with a long orbit time, the loosely bound Rydberg electron is not affected by the intense laser pulse. Instead the inner electron is ejected by absorption of five photons, leaving the ${\mathrm{Ba}}^{+}$ ion in a Rydberg state. For low-n states the outer electron is ejected and the residual ${\mathrm{Ba}}^{+}$ ion can subsequently be multiphoton ionized to ${\mathrm{Ba}}^{++}$.

Physical Review LettersDec 2, 199156 citations

Population trapping in Kr and Xe in intense laser fields

R. R. Jones, Douglass W. Schumacher, P. H. Bucksbaum

We have observed trapping of population in Rydberg states of atoms and ions exposed to intense laser radiation. The trapping occurs in nonstationary ``wave-packet'' superposition states, created, via ac Stark-shifted multiphoton resonances during the laser pulse. The formation of these highly excited bound states requires the nonresonant absorption of up to 20 or more photons; some of the ionic Rydberg states lie nearly 32 eV above the ionic ground state. All of the trapped states having binding energies much less than the photon energy but remain stable against ionization even when the multiphoton ionization probability of the atom is saturated.We have observed trapping of population in Rydberg states of atoms and ions exposed to intense laser radiation. The trapping occurs in nonstationary ``wave-packet'' superposition states, created, via ac Stark-shifted multiphoton resonances during the laser pulse. The formation of these highly excited bound states requires the nonresonant absorption of up to 20 or more photons; some of the ionic Rydberg states lie nearly 32 eV above the ionic ground state. All of the trapped states having binding energies much less than the photon energy but remain stable against ionization even when the multiphoton ionization probability of the atom is saturated.

Physical Review AJan 1, 199397 citations

Rydberg states in multiphoton atomic ionization processes

G. K. Ivanov, Gennady V. Golubkov, Dmitry Manakov

Journal of Experimental and Theoretical PhysicsNov 1, 19943 citations

Multiphoton ionization dynamics of barium Rydberg states in intense femtosecond pulses

Duncan Tate, Thomas F. Gallagher

We have investigated multiphoton ionization of Ba $6snl$ Rydberg states by intense 200-fs laser pulses. Specifically, we have excited Ba atoms to the $6sns$ and $6snd$ 15\ensuremath{\infty} states using two nanosecond lasers. The atoms were then irradiated with the fs pulses produced by a mode-locked, regeneratively amplified Ti:sapphire laser that is stepwise-tunable between 790 and 850 nm. We have used both the fundamental light and the second harmonic (395--425 nm) to investigate the ionization dynamics in these two wavelength regions. In contrast to previous experiments, in which laser pulses 5 ps or longer were used, our results indicate that excitation of ${\mathrm{Ba}}^{+}$ Rydberg states and ${\mathrm{Ba}}^{2+}$ photoions is relatively insensitive to the femtosecond laser wavelength. In addition, we find that, as the Kepler orbital period of the Ba Rydberg electron becomes comparable to this very small laser pulse width, the inner electron ionization process no longer appears to be instantaneous to the outer electron, and the outer electron is not projected onto ${\mathrm{Ba}}^{+}$ Rydberg states.We have investigated multiphoton ionization of Ba $6snl$ Rydberg states by intense 200-fs laser pulses. Specifically, we have excited Ba atoms to the $6sns$ and $6snd$ 15\ensuremath{\infty} states using two nanosecond lasers. The atoms were then irradiated with the fs pulses produced by a mode-locked, regeneratively amplified Ti:sapphire laser that is stepwise-tunable between 790 and 850 nm. We have used both the fundamental light and the second harmonic (395--425 nm) to investigate the ionization dynamics in these two wavelength regions. In contrast to previous experiments, in which laser pulses 5 ps or longer were used, our results indicate that excitation of ${\mathrm{Ba}}^{+}$ Rydberg states and ${\mathrm{Ba}}^{2+}$ photoions is relatively insensitive to the femtosecond laser wavelength. In addition, we find that, as the Kepler orbital period of the Ba Rydberg electron becomes comparable to this very small laser pulse width, the inner electron ionization process no longer appears to be instantaneous to the outer electron, and the outer electron is not projected onto ${\mathrm{Ba}}^{+}$ Rydberg states.

Physical Review AOct 1, 19985 citations

Multiphoton ionization of highly excited atomic states

I. Berson

Journal of Experimental and Theoretical PhysicsOct 1, 19821 citation

{\mathrm{Ba}}^{+}

ion in a Rydberg state. For low-n states the outer electron is ejected and the residual

{\mathrm{Ba}}^{+}

ion can subsequently be multiphoton ionized to

{\mathrm{Ba}}^{++}

We have investigated multiphoton ionization of Ba

6snl

Rydberg states by intense 200-fs laser pulses. Specifically, we have excited Ba atoms to the

6sns

and

6snd

15\ensuremath{\infty} states using two nanosecond lasers. The atoms were then irradiated with the fs pulses produced by a mode-locked, regeneratively amplified Ti:sapphire laser that is stepwise-tunable between 790 and 850 nm. We have used both the fundamental light and the second harmonic (395--425 nm) to investigate the ionization dynamics in these two wavelength regions. In contrast to previous experiments, in which laser pulses 5 ps or longer were used, our results indicate that excitation of

{\mathrm{Ba}}^{+}

Rydberg states and

{\mathrm{Ba}}^{2+}

photoions is relatively insensitive to the femtosecond laser wavelength. In addition, we find that, as the Kepler orbital period of the Ba Rydberg electron becomes comparable to this very small laser pulse width, the inner electron ionization process no longer appears to be instantaneous to the outer electron, and the outer electron is not projected onto

{\mathrm{Ba}}^{+}

Rydberg states.