the widgets of richfaces 4 can't manage effects contrary to RF 3.X.
the following code snippet is an example that show you how to add a "slide" effect to the <rich:accordion>
widget:
<rich:jQuery selector=".rf-ac .rf-ac-itm" event="click" query="
var elAccordion = $(this).parent('.rf-ac').first();
if (elAccordion.find('.lastAccordionItem').length == 0) {
elAccordion.find('div.rf-ac-itm-cnt').first().addClass('lastAccordionItem');
}
elAccordion.find('.lastAccordionItem').css('display','block');
elAccordion.find('.lastAccordionItem').slideUp();
elAccordion.find('.lastAccordionItem').removeClass('lastAccordionItem');
$(this).find('div.rf-ac-itm-cnt').css('display','none');
$(this).find('div.rf-ac-itm-cnt').slideDown();
$(this).find('div.rf-ac-itm-cnt').addClass('lastAccordionItem');
"/>
Typically, this code can be placed in a JSF2/facelet template.
Enjoy.